The western flower thrips, Frankliniella occidentalis, is one of the most destructive sucking pests of vegetables, fruits and ornamental crops in China. Spinosad is one of the most commonly used insecticides to manage...The western flower thrips, Frankliniella occidentalis, is one of the most destructive sucking pests of vegetables, fruits and ornamental crops in China. Spinosad is one of the most commonly used insecticides to manage thrips. To assess the incidence of spinosad resistance in F. occidentalis field populations in eastern China, survival rates for 24 different populations were compared with those of a susceptible laboratory strain. All populations showed significantly higher resistance to spinosad compared with the control as determined by comparing median lethal concentrations. Two populations from Shouguang and Liaocheng in Shandong Province were classified as having moderate and high levels of resistance to spinosad with a mean resistance ratio of 17.0 and 89.2, respectively. Our research indicates a widespread reduction in spinosad efficacy for controlling F. occidentalis field populations, and that resistance management strategies should be implemented as soon as practicable, to reduce the potential of progressive resistance development and loss of efficacy.展开更多
Identification and deployment of high-yielding and stress-tolerant maize hybrids adapted to stress-prone agro-ecologies is important for improving the food security and livelihoods of smallholder farmers in eastern Af...Identification and deployment of high-yielding and stress-tolerant maize hybrids adapted to stress-prone agro-ecologies is important for improving the food security and livelihoods of smallholder farmers in eastern Africa.The objectives of this study were to(i)assess the performance of maize hybrids under well-watered and drought stress conditions;(ii)evaluate grain yield stability of 65 intermediate-maturing and 55 early-maturing hybrids in 24 well-watered locations and seven drought stress locations;and(iii)identify representative and/or discriminative testing locations for increasing genetic gains for the target traits.There were significant differences for grain yield among early-and intermediatematuring hybrids tested under well-watered and drought stress environments.Among the early-maturing hybrids,the top 10 hybrids produced 46.8%–73.9%and 31.2%–42.1%higher mean grain yields than the best commercial check under drought and well-watered conditions,respectively.Among the intermediate-maturing hybrids,the top 10 hybrids produced 25.2%–47.7%and 8.5%–13.5%higher grain yield than commercial checks under drought stress and well-watered conditions,respectively,suggesting improvement in the levels of drought tolerance in both early-and intermediate-maturing hybrids.GGE biplot analysis and a bi-segmented regression linear method identified specific early-maturing and intermediate-maturing hybrids that performed well under both well-watered and drought stress conditions.These hybrids could be recommended for commercial production in eastern Africa.Kakamega in Kenya was found to be the most representative and highly discriminating site among well-watered testing locations,while Kabuku in Tanzania was the least representative of test locations.For testing under drought stress conditions,Kiboko in Kenya was identified as the most representative location.This information could be useful for allocating resources and streamlining CIMMYT maize hybrid testing in eastern Africa.展开更多
Five field trials were conducted over a two-year period (2013, 2014) to determine the control of glyphosate-resistant (GR) giant ragweed with isoxaflutole (IFT) and metribuzin (MTZ) applied alone and in combination. T...Five field trials were conducted over a two-year period (2013, 2014) to determine the control of glyphosate-resistant (GR) giant ragweed with isoxaflutole (IFT) and metribuzin (MTZ) applied alone and in combination. Treatments were designed to assess the dose response of an IFT plus MTZ tank-mix as well as each chemical applied alone to classify the response using Flint’s adaptation of Colby’s equation. Two factor factorial experiments were performed in the growth room to ascertain the response of IFT versus glyphosate, IFT versus MTZ, and IFT plus MTZ versus glyphosate on single plants. Field experiments evaluated the control of GR giant ragweed with IFT plus MTZ in tank-mix in a 1:4 ratio. The rate of IFT plus MTZ for 80% control of GR giant ragweed at 4 and 8 weeks after application (WAA) was 518 (104 g a.i. ha<sup>-1</sup> IFT + 414 g a.i. ha<sup>-1</sup> MTZ) and 631 g a.i. ha<sup>-1</sup> (126 g a.i. ha<sup>-1</sup> IFT + 505 g a.i. ha<sup>-1</sup> MTZ), respectively. A rate of 668 and 467 g a.i. ha<sup>-1</sup> was required to reduce GR giant ragweed density and biomass by 80%, respectively. Field experiments evaluating the control of GR giant ragweed with tank-mixes of IFT plus MTZ, where glyphosate was a constant tank-mix partner, were mostly synergistic. However, the low tank-mix rate (52.5 + 210 g a.i. ha<sup>-1</sup>) had an additive response for GR giant ragweed biomass reduction. When tested in the greenhouse and growth room, glyphosate susceptible (GS) giant ragweed showed some antagonism with glyphosate and isoxaflutole tank-mixes at rates less than commercial field rates. GR giant ragweed showed an additive response across all treatments in the growth room. Greenhouse experiments evaluating IFT versus MTZ and IFT plus MTZ versus glyphosate revealed all tank-mix treatments to be synergistic at 2 WAA.展开更多
Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter &l...Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter < 10 μm (PM<sub>10</sub>) from cattle feedlots. Meteorological conditions were measured and PM<sub>10</sub> concentrations were profiled vertically (i.e., 2.0 to 7.62 m) at a large commercial beef cattle feedlot in Kansas from May through September 2011. Results show that between the two methods evaluated, WindTrax was least sensitive to changes in heights and number of heights used in the emission estimation, with calculated PM<sub>10</sub> emission rates varying by up to 18% only. On the other hand, PM<sub>10</sub> emission rates produced by the flux-gradient technique varied by almost 56% when changing either heights and/or number of heights in emission calculation. Both methods were sensitive to height settings, with their respective PM<sub>10</sub> emission rates higher when the lowest height setting (2.0 m) was included. Calculating PM<sub>10</sub> emission rates with the 7.62-m height led to lower estimates for the flux-gradient technique but no significant change in estimates was observed for WindTrax. As demonstrated in this study, for the flux-gradient technique, settings for the lowest and highest heights were the most critical in emission estimation;exclusion of other heights in between showed only to 2% to 6% change in calculated PM<sub>10</sub> emission rates. In general, the higher PM<sub>10</sub> emission rates were obtained with the flux-gradient technique. However, eliminating the lowest height (2.0 m) in the calculation and, at the same time, using a specific set of formulations for the flux-gradient technique made its calculated PM<sub>10</sub> emission rates slightly lower (but not significantly different) than those from WindTrax.展开更多
In the U.S.,Helicoverpa zea(Boddie)is a major pest targeted by both transgenic maize and cotton expressing Bacillus thuringiensis(Bt)proteins.Resistance of insect to Bt maize and cotton containing cry1A and cry2A gene...In the U.S.,Helicoverpa zea(Boddie)is a major pest targeted by both transgenic maize and cotton expressing Bacillus thuringiensis(Bt)proteins.Resistance of insect to Bt maize and cotton containing cry1A and cry2A genes has widely occurred in the U.S.In this study,two trials were performed to investigate larval survival and development of a Cry1A.105/Cry2Ab2 dual-protein resistant(VT2P-RR),a susceptible,and an F1 heterozygous(VT2P-RS)populations of H.zea on ears of nine Bt and three non-Bt maize hybrids.The Bt maize hybrids evaluated represent five common pyramided traits expressing two or three of the Cry1A.105,Cry1Ab,Cry1F,Cry2Ab2,and Vip3Aa20 proteins.In the laboratory,neonates of the three H.zea populations were inoculated on silks of ears collected from maize at R1-R2 plant stages;and larval survivorship was checked 10 d after neonate release.All three insect populations survived normally on non-Bt maize ears.Varied numbers of VT2P-RR and VT2P-RS survived on ears of Cry1A.105/Cry2Ab2 maize,while all larvae of the three populations died or could not develop on ears of Vip3Aa20-expressing maize.The results demonstrated that the dual-protein resistant H.zea was not cross-resistant to Vip3Aa20-expressing maize,and thus traits with vip3Aa20 gene should be effective to manage Cry1A.105/Cry2Ab2-resistant H.zea.The resistance in VT2P-RR was determined to be incomplete on Cry1A.105/Cry2Ab2 maize.The effective dominance levels varied greatly,from recessive to incompletely dominant,depending on maize hybrids and trials,suggesting that proper selection of maize hybrids could be important for mitigating the Cry1A.105/Cry2Ab2 resistance.The data generated should aid in modeling multiple-protein Bt resistance in H.zea.展开更多
Water-logging and the inability to take up sufficient iron (Fe), causing iron deficiency chlorosis (IDC) in soybean (<em>Glycine max</em>, L. Merr.), can be major yield reducing factors in certain soils in...Water-logging and the inability to take up sufficient iron (Fe), causing iron deficiency chlorosis (IDC) in soybean (<em>Glycine max</em>, L. Merr.), can be major yield reducing factors in certain soils in the northern USA and Manitoba, Canada, soybean growing regions. The objective of this research was to evaluate soybean IDC, biomass production, and yield with seeding on raised beds and seed application of the Fe-chelate compound ortho-ortho-Fe-EDDHA. In six environments, soybean were seeded on raised beds and conventionally prepared seedbeds (flat) and with a factorial arrangement of five cultivars (within adapted maturity group 0.1 to 0.9 and variable IDC tolerance) and seed applied Fe-EDDHA using rates of 0 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup> and 3.36 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>. There were no significant interactions between the factors tested. The plant population was 27% higher on the raised beds compared with flat, and yield was 6.3% higher (2893 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup> vs. 2722 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>). Total dry plant biomass on raised beds was 9.8% greater compared with flat. The plant population with seed applied Fe-EDDHA was 10.6% lower compared with no application. However, the IDC score was significantly lower 2.2 vs 2.4 (1 = green, 5 = dead) for Fe-EDDHA seed application. Yield and plant biomass were not significantly different between Fe treatments. Raised beds offer an opportunity for soybean growers to reduce the negative influence of excessive water. Further research is needed to determine the long-term effect of raised beds on plant development, IDC expression, and yield. The application of Fe-EDDHA remains a partial solution and should therefore be combined with other methods to reduce IDC. Further research should study other Fe-EDDHA application rates and methods.展开更多
DNA methylation and demethylation activities are coordinated to maintain DNA methylation patterns.However,the interplay between them remains to be explored.In this study,we found that loss of DNA demethylase in maize ...DNA methylation and demethylation activities are coordinated to maintain DNA methylation patterns.However,the interplay between them remains to be explored.In this study,we found that loss of DNA demethylase in maize results in a significant decrease in CHH methylation,a hallmark of RNA-directed DNA methylation(RdDM).Further analyses suggested that this is caused by reduced expression in the DNA demethylase mutant of three CLASSY(CLSY)genes,which encode chromatin remodelers controlling small RNA production.Series of molecular assays confirm that the expression of three maize CLSY genes is sensitive to the DNA methylation levels at their promoter regions,which are regulated by both the DNA demethylase and the RdDM pathway.Moreover,we revealed that Arabidopsis DNA demethylase mutants also show decreased CHH methylation and reduced expression of CLSY1,one of four CLSY genes in Arabidopsis.Similar to the observations in maize,the expression of CLSY1 is associated with DNA methylation levels of its promoter that is targeted by both DNA demethylase and RdDM pathways.Taken together,these results suggest a conserved interplay between DNA demethylation and RdDM pathways,revealing a mechanism to maintain the homeostasis of DNA methylation levels across plants.展开更多
Helicoverpa zea is a major target pest of Bt corn and Bt cotton.Field-evolved resistance of H.zea to Cry1 and Cry2 proteins has been widely reported in the United States.Understanding the frequency of resistance allel...Helicoverpa zea is a major target pest of Bt corn and Bt cotton.Field-evolved resistance of H.zea to Cry1 and Cry2 proteins has been widely reported in the United States.Understanding the frequency of resistance alleles in a target insect is critical for Bt resistance management.Despite multiple cases of practical resistance to Cry proteins having been documented in H.zea,there are no data on the current status of alleles conferring resistance to Cry1Ac and Cry2Ab2 in field populations of this pest.During 2018‒2019,a total of 106 F2 families for Cry1Ac and 120 F2 families for Cry2Ab2 were established using mass mating and light trap strategy.We screened 13,568 and 15,360 neonates using a discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The results showed that 93.4%and 35.0%of the F2 families could survive on the discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The estimated resistance allele frequency for Cry1Ac in H.zea ranged from 0.4150 to 0.4975 and for Cry2Ab2 ranged from 0.1097 and 0.1228.These data indicate that the frequency of alleles conferring resistance to Cry1 and Cry2 proteins in H.zea in Texas are high.In addition,our data suggest the resistance to Cry1Ac and Cry2Ab2 in the screened families of H.zea varies from recessive to dominant.The information in this study provides precise estimates of Cry resistance allele frequencies in H.zea and increases our understanding of the risks to the sustainability of Bt crops.展开更多
Robust genome editing technologies are becoming part of the crop breeding toolbox.Currently,genome editing is usually conducted either at a single locus,or multiple loci,in a variety at one time.Massively parallel gen...Robust genome editing technologies are becoming part of the crop breeding toolbox.Currently,genome editing is usually conducted either at a single locus,or multiple loci,in a variety at one time.Massively parallel genomics platforms,multifaceted genome editing capabilities,and flexible transformation systems enable targeted variation at nearly any locus,across the spectrum of genotypes within a species.We demonstrate here the simultaneous transformation and editing of many genotypes,by targeting mixed seed embryo explants with genome editing machinery,followed by re-identification through genotyping after plant regeneration.Transformation and Editing of Mixed Lines(TREDMIL)produced transformed individuals representing 101 of 104(97%)mixed elite genotypes in soybean;and 22 of 40(55%)and 9 of 36(25%)mixed maize female and male elite inbred genotypes,respectively.Characterization of edited genotypes for the regenerated individuals identified over 800 distinct edits at the Determinate1(Dt1)locus in samples from 101 soybean genotypes and 95 distinct Brown midrib3(Bm3)edits in samples from 17 maize genotypes.These results illustrate how TREDMIL can help accelerate the development and deployment of customized crop varieties for future precision breeding.展开更多
To sustain plant growth,development,and crop yield,sucrose must be transported from leaves to distant parts of the plant,such as seeds and roots.To identify genes that regulate sucrose accumulation and transport in ma...To sustain plant growth,development,and crop yield,sucrose must be transported from leaves to distant parts of the plant,such as seeds and roots.To identify genes that regulate sucrose accumulation and transport in maize(Zea mays),we isolated carbo/iydrafe part/f/ofi/ngf defecf/Ve33(cpd33),a recessive mutant that accumulated excess starch and soluble sugars in mature leaves.The cpd33 mutants also exhibited chlorosis in the leaf blades,greatly diminished plant growth,and reduced fertility.Cpd33 encodes a protein containing multiple C2 domains and transmembrane regions.Subcellular localization experiments showed the CPD33 protein localized to plasmodesmata(PD),the plasma membrane,and the endoplasmic reticulum.We also found that a loss-of-function mutant of the CPD33 homolog in Arabidopsis,QUIRKY,had a similar carbohydrate hyperaccumulation phenotype.Radioactively labeled sucrose transport assays showed that sucrose export was significantly lower in cpd33 mutant leaves relative to wild-type leaves.However,PD transport in the adaxial-abaxial direction was unaffected in cpd33 mutant leaves.Intriguingly,transmission electron microscopy revealed fewer PD at the companion cell-sieve element interface in mutant phloem tissue,providing a possible explanation for the reduced sucrose export in mutant leaves.Collectively,our results suggest that CPD33 functions to promote symplastic transport into sieve elements.展开更多
A seed blend refuge has been implemented in the U.S.Corn Belt for Bt maize resistance management.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a target pest of Bt maize in the Americas.The larvae of this pest ...A seed blend refuge has been implemented in the U.S.Corn Belt for Bt maize resistance management.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a target pest of Bt maize in the Americas.The larvae of this pest are mobile,which may affect the efficacy of seed blend refuges.In this study,field and greenhouse trials were conducted to determine the performance of Bt-susceptible(aabb)and-heterozygous dual-gene-resistant(AaBb)genotypes of S.frugiperda in seed blends of non-Bt and pyramided Bt maize.Three field trials evaluated larval survival,larval growth,and plant injury with aabb in seed blends of Bt maize expressing Cry1A.105/Cry2Ab2/Vip3A with 0–30%non-Bt seeds.Greenhouse tests investigated the performance of aabb and AaBb in seed blends of Cry1A.105/Cry2Ab2 with 0–30% non-Bt seeds.In pure non-Bt maize plots,after 9–13 d of neonates being released on the plants,0.39 and 0.65 larvae/plant survived with leaf injury ratings of 4.7 and 5.9(Davis's 1–9 scale)in the field and greenhouse,respectively.In contrast,live larvae and plant injury were virtually not observed on Bt plants across all planting patterns.Larval occurrence and plant injury by aabb on non-Bt plants were similar between seed blends and pure non-Bt plantings,suggesting that the blended refuges could provide an equivalent susceptible population as structured refuge under the test conditions.In the greenhouse,the two insect genotypes in seed blends performed similarly,indicating that the seed blends did not provide more favorable conditions for AaBb over aabb.The information generated from this study should be useful in managing S.frugiperda and evaluating if send blends could be suitable refuge options for Bt resistance management in the regions where the insect is a primary target pest.展开更多
Cultivated potato is a clonally propagated autotetraploid species with a highly heterogeneous genome.Phased assemblies of six cultivars including two chromosome-scale phased genome assemblies revealed extensive alleli...Cultivated potato is a clonally propagated autotetraploid species with a highly heterogeneous genome.Phased assemblies of six cultivars including two chromosome-scale phased genome assemblies revealed extensive allelic diversity,including altered coding and transcript sequences,preferential allele expression,and structural variation that collectively result in a highly complex transcriptome and predicted proteome,which are distributed across the homologous chromosomes.Wild species contribute to the extensive allelic diversity in tetraploid cultivars,demonstrating ancestral introgressions predating modern breeding efforts.As a clonally propagated autotetraploid that undergoes limited meiosis,dysfunctional and deleterious alleles are not purged in tetraploid potato.Nearly a quarter of the loci bore mutations are predicted to have a high negative impact on protein function,complicating breeder’s efforts to reduce genetic load.The StCDF1 locus controls maturity,and analysis of six tetraploid genomes revealed that 12 allelic variants of StCDF1 are correlated with maturity in a dosage-dependent manner.Knowledge of the complexity of the tetraploid potato genome with its rampant structural variation and embedded deleterious and dysfunctional alleles will be key not only to implementing precision breeding of tetraploid cultivars but also to the construction of homozygous,diploid potato germplasm containing favorable alleles to capitalize on heterosis in F1 hybrids.展开更多
Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widel...Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034.In this study,two tests(Test-Ⅰ and Test-Ⅱ)were conducted to evaluate the relative fitness of Bt-susceptible and-resistant H.zea on non-Bt diet(Test-Ⅰ and Test-Ⅱ)and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration(Test-Ⅱ only).Insect populations evaluated in Test-Ⅰ were two Bt-susceptible strains and three Bt-resistant strains(a single-protein Cry1A.105-,a single-protein Cry2Ab2-,and a dual-protein Cry1A.105/Cry2Ab2-resistant strains).Test-Ⅱ analyzed the same two susceptible strains,three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains,and three F1 heterozygous strains.Measurements of life table parameters showed that neither the single-nor dual-protein Cry1A.105/Cry2Ab2 resistance in H.zea was associated with fitness costs under the test conditions.The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant,and the dual-protein resistance was completely dominant.The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species.Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H.zea.展开更多
Polyamines are small aliphatic amines found in almost all organisms,ranging from bacteria to plants and animals.In most plants,putrescine,the metabolic precursor for longer polyamines,such as spermidine and spermine,i...Polyamines are small aliphatic amines found in almost all organisms,ranging from bacteria to plants and animals.In most plants,putrescine,the metabolic precursor for longer polyamines,such as spermidine and spermine,is produced from arginine,with either agmatine or ornithine as intermediates.Here we show that Arabidopsis thaliana(Arabidopsis)arginine de-carboxylase 1(ADC1),one of the two known arginine decarboxylases in Arabidopsis,not only synthesizes agmatine from arginine,but also converts N-acety.lornithine to N-acetylputrescine.Phylogenetic analyses indicate that duplication and neofunctionalization of ADC1 and NATA1,the enzymes that synthesize Nδ-acetylormithine in Arabidopsis,co-occur in a small number of related species in the Brassicaceae.Unlike ADC2,which is localized in the chloroplasts,ADC1 is in the endoplasmic reticulum together with NATA1,an indication that these two enzymes have access to the same substrate pool.Together,these results are con-sistent with a model whereby NATA1 and ADC1 to-gether provide a pathway for the synthesis of N-acetylputrescine in Arabidopsis.展开更多
Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern US...Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern USA.Methods:One thousand tall fescue genotypes were evaluated in the greenhouse for high relative water content(RWC)and low cell sap osmotic potential(OP).Fifty contrasting genotypes for the two traits were identified and used in further greenhouse and field studies.These genotypes were also screened with 30%PEG8000.Root and shoot characteristics were studied in 10 genotypes.Results:The genotypes differed for RWC(33.7%–97.3%,mean:79.7%)and had an almost fivefold difference in OP(−0.5 to−2.4 MPa,mean:−1.2 MPa).Significant variation(p<0.001)for the main effects of environment and genotypes was found for RWC and OP.Apart from the greenhouse trial,no correlation was found between RWC and OP,indicating that differences in RWC might have been due to factors other than osmotic adjustment.Genotypes with either long roots or high root weights,and high root/shoot ratios demonstrated high RWC and low OP.Conclusions:Genotypes with consistently high RWC and low OP were identified and used for the development of mapping populations and transcriptome studies.展开更多
基金financially supported by the National Natural Science Foundation of China (31371942)the National Key Research and Development Program,China (2016YFC1200600)the Ministry of Science and Technology,China
文摘The western flower thrips, Frankliniella occidentalis, is one of the most destructive sucking pests of vegetables, fruits and ornamental crops in China. Spinosad is one of the most commonly used insecticides to manage thrips. To assess the incidence of spinosad resistance in F. occidentalis field populations in eastern China, survival rates for 24 different populations were compared with those of a susceptible laboratory strain. All populations showed significantly higher resistance to spinosad compared with the control as determined by comparing median lethal concentrations. Two populations from Shouguang and Liaocheng in Shandong Province were classified as having moderate and high levels of resistance to spinosad with a mean resistance ratio of 17.0 and 89.2, respectively. Our research indicates a widespread reduction in spinosad efficacy for controlling F. occidentalis field populations, and that resistance management strategies should be implemented as soon as practicable, to reduce the potential of progressive resistance development and loss of efficacy.
基金supported by the Bill and Melinda Gates Foundationthe Howard G.Buffett Foundation+4 种基金the United States Agency for International Development(USAID)through the Water Efficient Maize for Africa(WEMA)projectthe Stress Tolerant Maize for Africa(STMA)projectthe CGIAR Research Program MAIZEThe CGIAR Research Program MAIZE receives W1&W2 support from the Governments of Australia,Belgium,Canada,China,France,India,Japan,the Republic of Korea,Mexico,the Netherlands,New Zealand,Norway,Sweden,Switzerland,United Kingdom,the United States,and the World BankBrazilian Coordination for the Improvement of Higher Education Personnel(CAPES)for a scholarship supporting Wender Rezende
文摘Identification and deployment of high-yielding and stress-tolerant maize hybrids adapted to stress-prone agro-ecologies is important for improving the food security and livelihoods of smallholder farmers in eastern Africa.The objectives of this study were to(i)assess the performance of maize hybrids under well-watered and drought stress conditions;(ii)evaluate grain yield stability of 65 intermediate-maturing and 55 early-maturing hybrids in 24 well-watered locations and seven drought stress locations;and(iii)identify representative and/or discriminative testing locations for increasing genetic gains for the target traits.There were significant differences for grain yield among early-and intermediatematuring hybrids tested under well-watered and drought stress environments.Among the early-maturing hybrids,the top 10 hybrids produced 46.8%–73.9%and 31.2%–42.1%higher mean grain yields than the best commercial check under drought and well-watered conditions,respectively.Among the intermediate-maturing hybrids,the top 10 hybrids produced 25.2%–47.7%and 8.5%–13.5%higher grain yield than commercial checks under drought stress and well-watered conditions,respectively,suggesting improvement in the levels of drought tolerance in both early-and intermediate-maturing hybrids.GGE biplot analysis and a bi-segmented regression linear method identified specific early-maturing and intermediate-maturing hybrids that performed well under both well-watered and drought stress conditions.These hybrids could be recommended for commercial production in eastern Africa.Kakamega in Kenya was found to be the most representative and highly discriminating site among well-watered testing locations,while Kabuku in Tanzania was the least representative of test locations.For testing under drought stress conditions,Kiboko in Kenya was identified as the most representative location.This information could be useful for allocating resources and streamlining CIMMYT maize hybrid testing in eastern Africa.
文摘Five field trials were conducted over a two-year period (2013, 2014) to determine the control of glyphosate-resistant (GR) giant ragweed with isoxaflutole (IFT) and metribuzin (MTZ) applied alone and in combination. Treatments were designed to assess the dose response of an IFT plus MTZ tank-mix as well as each chemical applied alone to classify the response using Flint’s adaptation of Colby’s equation. Two factor factorial experiments were performed in the growth room to ascertain the response of IFT versus glyphosate, IFT versus MTZ, and IFT plus MTZ versus glyphosate on single plants. Field experiments evaluated the control of GR giant ragweed with IFT plus MTZ in tank-mix in a 1:4 ratio. The rate of IFT plus MTZ for 80% control of GR giant ragweed at 4 and 8 weeks after application (WAA) was 518 (104 g a.i. ha<sup>-1</sup> IFT + 414 g a.i. ha<sup>-1</sup> MTZ) and 631 g a.i. ha<sup>-1</sup> (126 g a.i. ha<sup>-1</sup> IFT + 505 g a.i. ha<sup>-1</sup> MTZ), respectively. A rate of 668 and 467 g a.i. ha<sup>-1</sup> was required to reduce GR giant ragweed density and biomass by 80%, respectively. Field experiments evaluating the control of GR giant ragweed with tank-mixes of IFT plus MTZ, where glyphosate was a constant tank-mix partner, were mostly synergistic. However, the low tank-mix rate (52.5 + 210 g a.i. ha<sup>-1</sup>) had an additive response for GR giant ragweed biomass reduction. When tested in the greenhouse and growth room, glyphosate susceptible (GS) giant ragweed showed some antagonism with glyphosate and isoxaflutole tank-mixes at rates less than commercial field rates. GR giant ragweed showed an additive response across all treatments in the growth room. Greenhouse experiments evaluating IFT versus MTZ and IFT plus MTZ versus glyphosate revealed all tank-mix treatments to be synergistic at 2 WAA.
文摘Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter < 10 μm (PM<sub>10</sub>) from cattle feedlots. Meteorological conditions were measured and PM<sub>10</sub> concentrations were profiled vertically (i.e., 2.0 to 7.62 m) at a large commercial beef cattle feedlot in Kansas from May through September 2011. Results show that between the two methods evaluated, WindTrax was least sensitive to changes in heights and number of heights used in the emission estimation, with calculated PM<sub>10</sub> emission rates varying by up to 18% only. On the other hand, PM<sub>10</sub> emission rates produced by the flux-gradient technique varied by almost 56% when changing either heights and/or number of heights in emission calculation. Both methods were sensitive to height settings, with their respective PM<sub>10</sub> emission rates higher when the lowest height setting (2.0 m) was included. Calculating PM<sub>10</sub> emission rates with the 7.62-m height led to lower estimates for the flux-gradient technique but no significant change in estimates was observed for WindTrax. As demonstrated in this study, for the flux-gradient technique, settings for the lowest and highest heights were the most critical in emission estimation;exclusion of other heights in between showed only to 2% to 6% change in calculated PM<sub>10</sub> emission rates. In general, the higher PM<sub>10</sub> emission rates were obtained with the flux-gradient technique. However, eliminating the lowest height (2.0 m) in the calculation and, at the same time, using a specific set of formulations for the flux-gradient technique made its calculated PM<sub>10</sub> emission rates slightly lower (but not significantly different) than those from WindTrax.
基金This article is published with the approval of the Director of the Louisiana Agricultural Experiment Station as manuscript No.2022-234-37238This project represents work supported by Bayer Crop Science(St.Louis,MO,USA)the Hatch funds from the USDA National Institute of Food and Agriculture,and the USDA Regional Research Project NC-246.
文摘In the U.S.,Helicoverpa zea(Boddie)is a major pest targeted by both transgenic maize and cotton expressing Bacillus thuringiensis(Bt)proteins.Resistance of insect to Bt maize and cotton containing cry1A and cry2A genes has widely occurred in the U.S.In this study,two trials were performed to investigate larval survival and development of a Cry1A.105/Cry2Ab2 dual-protein resistant(VT2P-RR),a susceptible,and an F1 heterozygous(VT2P-RS)populations of H.zea on ears of nine Bt and three non-Bt maize hybrids.The Bt maize hybrids evaluated represent five common pyramided traits expressing two or three of the Cry1A.105,Cry1Ab,Cry1F,Cry2Ab2,and Vip3Aa20 proteins.In the laboratory,neonates of the three H.zea populations were inoculated on silks of ears collected from maize at R1-R2 plant stages;and larval survivorship was checked 10 d after neonate release.All three insect populations survived normally on non-Bt maize ears.Varied numbers of VT2P-RR and VT2P-RS survived on ears of Cry1A.105/Cry2Ab2 maize,while all larvae of the three populations died or could not develop on ears of Vip3Aa20-expressing maize.The results demonstrated that the dual-protein resistant H.zea was not cross-resistant to Vip3Aa20-expressing maize,and thus traits with vip3Aa20 gene should be effective to manage Cry1A.105/Cry2Ab2-resistant H.zea.The resistance in VT2P-RR was determined to be incomplete on Cry1A.105/Cry2Ab2 maize.The effective dominance levels varied greatly,from recessive to incompletely dominant,depending on maize hybrids and trials,suggesting that proper selection of maize hybrids could be important for mitigating the Cry1A.105/Cry2Ab2 resistance.The data generated should aid in modeling multiple-protein Bt resistance in H.zea.
文摘Water-logging and the inability to take up sufficient iron (Fe), causing iron deficiency chlorosis (IDC) in soybean (<em>Glycine max</em>, L. Merr.), can be major yield reducing factors in certain soils in the northern USA and Manitoba, Canada, soybean growing regions. The objective of this research was to evaluate soybean IDC, biomass production, and yield with seeding on raised beds and seed application of the Fe-chelate compound ortho-ortho-Fe-EDDHA. In six environments, soybean were seeded on raised beds and conventionally prepared seedbeds (flat) and with a factorial arrangement of five cultivars (within adapted maturity group 0.1 to 0.9 and variable IDC tolerance) and seed applied Fe-EDDHA using rates of 0 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup> and 3.36 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>. There were no significant interactions between the factors tested. The plant population was 27% higher on the raised beds compared with flat, and yield was 6.3% higher (2893 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup> vs. 2722 kg<span style="white-space:nowrap;"><span style="white-space:nowrap;">·</span></span>ha<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>). Total dry plant biomass on raised beds was 9.8% greater compared with flat. The plant population with seed applied Fe-EDDHA was 10.6% lower compared with no application. However, the IDC score was significantly lower 2.2 vs 2.4 (1 = green, 5 = dead) for Fe-EDDHA seed application. Yield and plant biomass were not significantly different between Fe treatments. Raised beds offer an opportunity for soybean growers to reduce the negative influence of excessive water. Further research is needed to determine the long-term effect of raised beds on plant development, IDC expression, and yield. The application of Fe-EDDHA remains a partial solution and should therefore be combined with other methods to reduce IDC. Further research should study other Fe-EDDHA application rates and methods.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(32321005)the 111 Project Crop Genomics and Molecular Breeding(B20051)+1 种基金the Outstanding Youth Team Cultivation Project of Central Universities(2662023PY007)the Postdoctoral Fellowship Program of CPSF undergrantnumberGZB20240254.
文摘DNA methylation and demethylation activities are coordinated to maintain DNA methylation patterns.However,the interplay between them remains to be explored.In this study,we found that loss of DNA demethylase in maize results in a significant decrease in CHH methylation,a hallmark of RNA-directed DNA methylation(RdDM).Further analyses suggested that this is caused by reduced expression in the DNA demethylase mutant of three CLASSY(CLSY)genes,which encode chromatin remodelers controlling small RNA production.Series of molecular assays confirm that the expression of three maize CLSY genes is sensitive to the DNA methylation levels at their promoter regions,which are regulated by both the DNA demethylase and the RdDM pathway.Moreover,we revealed that Arabidopsis DNA demethylase mutants also show decreased CHH methylation and reduced expression of CLSY1,one of four CLSY genes in Arabidopsis.Similar to the observations in maize,the expression of CLSY1 is associated with DNA methylation levels of its promoter that is targeted by both DNA demethylase and RdDM pathways.Taken together,these results suggest a conserved interplay between DNA demethylation and RdDM pathways,revealing a mechanism to maintain the homeostasis of DNA methylation levels across plants.
基金supported by Biotechnology Risk Assessment grant no.2017-33522-27090/project accession no.1013740 from the USDA National Institute of Food and Agriculture.
文摘Helicoverpa zea is a major target pest of Bt corn and Bt cotton.Field-evolved resistance of H.zea to Cry1 and Cry2 proteins has been widely reported in the United States.Understanding the frequency of resistance alleles in a target insect is critical for Bt resistance management.Despite multiple cases of practical resistance to Cry proteins having been documented in H.zea,there are no data on the current status of alleles conferring resistance to Cry1Ac and Cry2Ab2 in field populations of this pest.During 2018‒2019,a total of 106 F2 families for Cry1Ac and 120 F2 families for Cry2Ab2 were established using mass mating and light trap strategy.We screened 13,568 and 15,360 neonates using a discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The results showed that 93.4%and 35.0%of the F2 families could survive on the discriminatory dose of Cry1Ac and Cry2Ab2,respectively.The estimated resistance allele frequency for Cry1Ac in H.zea ranged from 0.4150 to 0.4975 and for Cry2Ab2 ranged from 0.1097 and 0.1228.These data indicate that the frequency of alleles conferring resistance to Cry1 and Cry2 proteins in H.zea in Texas are high.In addition,our data suggest the resistance to Cry1Ac and Cry2Ab2 in the screened families of H.zea varies from recessive to dominant.The information in this study provides precise estimates of Cry resistance allele frequencies in H.zea and increases our understanding of the risks to the sustainability of Bt crops.
文摘Robust genome editing technologies are becoming part of the crop breeding toolbox.Currently,genome editing is usually conducted either at a single locus,or multiple loci,in a variety at one time.Massively parallel genomics platforms,multifaceted genome editing capabilities,and flexible transformation systems enable targeted variation at nearly any locus,across the spectrum of genotypes within a species.We demonstrate here the simultaneous transformation and editing of many genotypes,by targeting mixed seed embryo explants with genome editing machinery,followed by re-identification through genotyping after plant regeneration.Transformation and Editing of Mixed Lines(TREDMIL)produced transformed individuals representing 101 of 104(97%)mixed elite genotypes in soybean;and 22 of 40(55%)and 9 of 36(25%)mixed maize female and male elite inbred genotypes,respectively.Characterization of edited genotypes for the regenerated individuals identified over 800 distinct edits at the Determinate1(Dt1)locus in samples from 101 soybean genotypes and 95 distinct Brown midrib3(Bm3)edits in samples from 17 maize genotypes.These results illustrate how TREDMIL can help accelerate the development and deployment of customized crop varieties for future precision breeding.
文摘To sustain plant growth,development,and crop yield,sucrose must be transported from leaves to distant parts of the plant,such as seeds and roots.To identify genes that regulate sucrose accumulation and transport in maize(Zea mays),we isolated carbo/iydrafe part/f/ofi/ngf defecf/Ve33(cpd33),a recessive mutant that accumulated excess starch and soluble sugars in mature leaves.The cpd33 mutants also exhibited chlorosis in the leaf blades,greatly diminished plant growth,and reduced fertility.Cpd33 encodes a protein containing multiple C2 domains and transmembrane regions.Subcellular localization experiments showed the CPD33 protein localized to plasmodesmata(PD),the plasma membrane,and the endoplasmic reticulum.We also found that a loss-of-function mutant of the CPD33 homolog in Arabidopsis,QUIRKY,had a similar carbohydrate hyperaccumulation phenotype.Radioactively labeled sucrose transport assays showed that sucrose export was significantly lower in cpd33 mutant leaves relative to wild-type leaves.However,PD transport in the adaxial-abaxial direction was unaffected in cpd33 mutant leaves.Intriguingly,transmission electron microscopy revealed fewer PD at the companion cell-sieve element interface in mutant phloem tissue,providing a possible explanation for the reduced sucrose export in mutant leaves.Collectively,our results suggest that CPD33 functions to promote symplastic transport into sieve elements.
基金This article is published with the approval of the Director of the Louisiana Agri-cultural Experiment Station as manuscript No.2020-234-34595This project represents work supported by Bayer Crop Science(St.Louis,MO,USA),USDA Regional Research Project NC-246Hatch funds from the USDA National Institute of Food and Agriculture.
文摘A seed blend refuge has been implemented in the U.S.Corn Belt for Bt maize resistance management.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a target pest of Bt maize in the Americas.The larvae of this pest are mobile,which may affect the efficacy of seed blend refuges.In this study,field and greenhouse trials were conducted to determine the performance of Bt-susceptible(aabb)and-heterozygous dual-gene-resistant(AaBb)genotypes of S.frugiperda in seed blends of non-Bt and pyramided Bt maize.Three field trials evaluated larval survival,larval growth,and plant injury with aabb in seed blends of Bt maize expressing Cry1A.105/Cry2Ab2/Vip3A with 0–30%non-Bt seeds.Greenhouse tests investigated the performance of aabb and AaBb in seed blends of Cry1A.105/Cry2Ab2 with 0–30% non-Bt seeds.In pure non-Bt maize plots,after 9–13 d of neonates being released on the plants,0.39 and 0.65 larvae/plant survived with leaf injury ratings of 4.7 and 5.9(Davis's 1–9 scale)in the field and greenhouse,respectively.In contrast,live larvae and plant injury were virtually not observed on Bt plants across all planting patterns.Larval occurrence and plant injury by aabb on non-Bt plants were similar between seed blends and pure non-Bt plantings,suggesting that the blended refuges could provide an equivalent susceptible population as structured refuge under the test conditions.In the greenhouse,the two insect genotypes in seed blends performed similarly,indicating that the seed blends did not provide more favorable conditions for AaBb over aabb.The information generated from this study should be useful in managing S.frugiperda and evaluating if send blends could be suitable refuge options for Bt resistance management in the regions where the insect is a primary target pest.
基金We acknowledge financial support from AAFC-Genome Quebec GQAAC-2019-2 to M.V.S.,Agriculture and Agri-Food Canada Genomics Research and Development Initiative grant number J-002367 to H.H.T.and K.M.G.Compute Canada,Research Portals and Platforms(RPP)award to M.V.S,Compute Canada,Resources for Research Groups(RRG)award to M.V.S.,DFG Germany’s Excellence Strategy(EXC2048/1-Project 390686111)to B.U.,Dutch TKI top-sector project Novel genetic and genomic tools for polyploid crops(project numbers BO26.03-009-004 and BO-50-002-022)to P.M.B.,European Union’s Horizon 2020 research and innovation programme under grant agreement no 862858(ADAPT)to C.W.B.B.,Germany Ministry of Education and Research BMBF FKZ031A536C to B.U.,Germany Ministry of Education and Research BMBF FKZ031A536C to M.E.B.,GIZ on behalf of the of the Federal Ministry for Economic Cooperation and Development,Germany to D.Ellis and N.L.A.,National Science Foundation(IOS 2140176)to C.R.B.+6 种基金National Science Foundation NRT-IMPACTS fellowship(1828149)to N.B.,NC Agricultural Research Service to G.C.Y.,NC State University to G.C.Y.,NSF IOS-1929982 to C.R.B.NWO-domein Toegepaste en Technische Wetenschappen MAMY project ID 16889 to C.W.B.B.and N.L.,Potato Variety Management Institute to K.V.and V.S.,State of Minnesota,Minnesota Department of Agriculture to L.M.S.,the United States-Israel Binational Agricultural Research and Development Funds IS-5038-17C and IS-5317-20C to J.J.Texas A&M University to M.I.V.,The Clen P.and Emma L.Atchley Potato Research Faculty Excellence Endowment to J.C.K.,University of Maine to E.H.T.,USDA AFRI NIFA Pre-doctoral Fellowship project 2019-07160 to N.R.K.,USDA Multistate Research Funds accession 1004958 to W.S.D.J.USDA Hatch Act 2019-03162 to C.R.B.,USDA NIFA 2020-67034-31731 to G.H.USDA-NIFA 2016-34141-25707 to L.M.S.,USDA-NIFA-SCRI 2019-51181-30021 to L.M.S.,Dutch TKI top-sector project Genetics Assisted Assembly of Complex Genomes(project number BO-68-001-033-WPR)LWV20.112 Application of sequence-based multi-allelic markers in genetics and breeding of polyploids(project number BO-68-001-042-WPR)Wageningen UR Plant Breeding to R.F.,Wageningen UR Plant Breeding to R.G.F.V.,and Washington State Potato Commission to M.J.F.We would like to thank Emily McCoy and Martin Lague for assistance with data analysis.
文摘Cultivated potato is a clonally propagated autotetraploid species with a highly heterogeneous genome.Phased assemblies of six cultivars including two chromosome-scale phased genome assemblies revealed extensive allelic diversity,including altered coding and transcript sequences,preferential allele expression,and structural variation that collectively result in a highly complex transcriptome and predicted proteome,which are distributed across the homologous chromosomes.Wild species contribute to the extensive allelic diversity in tetraploid cultivars,demonstrating ancestral introgressions predating modern breeding efforts.As a clonally propagated autotetraploid that undergoes limited meiosis,dysfunctional and deleterious alleles are not purged in tetraploid potato.Nearly a quarter of the loci bore mutations are predicted to have a high negative impact on protein function,complicating breeder’s efforts to reduce genetic load.The StCDF1 locus controls maturity,and analysis of six tetraploid genomes revealed that 12 allelic variants of StCDF1 are correlated with maturity in a dosage-dependent manner.Knowledge of the complexity of the tetraploid potato genome with its rampant structural variation and embedded deleterious and dysfunctional alleles will be key not only to implementing precision breeding of tetraploid cultivars but also to the construction of homozygous,diploid potato germplasm containing favorable alleles to capitalize on heterosis in F1 hybrids.
基金supported by Bayer Crop Science(St.Louis,MO,USA),USDA Regional Research Project NC-246Hatch funds from the USDA National Institute of Food and Agriculture.
文摘Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034.In this study,two tests(Test-Ⅰ and Test-Ⅱ)were conducted to evaluate the relative fitness of Bt-susceptible and-resistant H.zea on non-Bt diet(Test-Ⅰ and Test-Ⅱ)and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration(Test-Ⅱ only).Insect populations evaluated in Test-Ⅰ were two Bt-susceptible strains and three Bt-resistant strains(a single-protein Cry1A.105-,a single-protein Cry2Ab2-,and a dual-protein Cry1A.105/Cry2Ab2-resistant strains).Test-Ⅱ analyzed the same two susceptible strains,three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains,and three F1 heterozygous strains.Measurements of life table parameters showed that neither the single-nor dual-protein Cry1A.105/Cry2Ab2 resistance in H.zea was associated with fitness costs under the test conditions.The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant,and the dual-protein resistance was completely dominant.The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species.Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H.zea.
基金funded by the Triad Foundation and United States National Science Foundation awards 1121788,1358843,and 1358843 to GJthe Graduate College at Bowling Green State University。
文摘Polyamines are small aliphatic amines found in almost all organisms,ranging from bacteria to plants and animals.In most plants,putrescine,the metabolic precursor for longer polyamines,such as spermidine and spermine,is produced from arginine,with either agmatine or ornithine as intermediates.Here we show that Arabidopsis thaliana(Arabidopsis)arginine de-carboxylase 1(ADC1),one of the two known arginine decarboxylases in Arabidopsis,not only synthesizes agmatine from arginine,but also converts N-acety.lornithine to N-acetylputrescine.Phylogenetic analyses indicate that duplication and neofunctionalization of ADC1 and NATA1,the enzymes that synthesize Nδ-acetylormithine in Arabidopsis,co-occur in a small number of related species in the Brassicaceae.Unlike ADC2,which is localized in the chloroplasts,ADC1 is in the endoplasmic reticulum together with NATA1,an indication that these two enzymes have access to the same substrate pool.Together,these results are con-sistent with a model whereby NATA1 and ADC1 to-gether provide a pathway for the synthesis of N-acetylputrescine in Arabidopsis.
文摘Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern USA.Methods:One thousand tall fescue genotypes were evaluated in the greenhouse for high relative water content(RWC)and low cell sap osmotic potential(OP).Fifty contrasting genotypes for the two traits were identified and used in further greenhouse and field studies.These genotypes were also screened with 30%PEG8000.Root and shoot characteristics were studied in 10 genotypes.Results:The genotypes differed for RWC(33.7%–97.3%,mean:79.7%)and had an almost fivefold difference in OP(−0.5 to−2.4 MPa,mean:−1.2 MPa).Significant variation(p<0.001)for the main effects of environment and genotypes was found for RWC and OP.Apart from the greenhouse trial,no correlation was found between RWC and OP,indicating that differences in RWC might have been due to factors other than osmotic adjustment.Genotypes with either long roots or high root weights,and high root/shoot ratios demonstrated high RWC and low OP.Conclusions:Genotypes with consistently high RWC and low OP were identified and used for the development of mapping populations and transcriptome studies.
