Allelopathy was defined in 1996 by IAS （international allelopathy society） as any process involving secondary metabolites produced by plant, algae, bacteria and fungi that influences the growth and development of ag...Allelopathy was defined in 1996 by IAS （international allelopathy society） as any process involving secondary metabolites produced by plant, algae, bacteria and fungi that influences the growth and development of agricultural and biological systems. Rice allelopathy against weeds was reported since 1989, which offers an integrated weed management with substantially reduced herbicide usage. Application of allelopathic rice cultivars is thought a resources conservation and environmental friendly way of weed bio-control, and could promote the sustainable development of agriculture. Screening or evaluating the allelopathic potential rice variety is the first step. In this paper, a new bioassay method was set up by the allelopathic potential of 9 rice lines on the target weed barnyardgrass （Echinochloa crusgalli）, and comparing with bioassay methods such as relay seeding in filter paper （RSF） and relay seeding in agar （RSA）. The results indicated that three methods had a same tendency in evaluating the allelopathic potential of rice; there existed a significant difference among different bioassay methods, and an interaction between bioassay methods and rice lines. The method of root exudates （RE） with the highest value and a correlation efficiency of 0.98 was considered as ideal bioassay method for evaluation of allelopathic potential.展开更多
The beet armyworm(BAW),Spodoptera exigua(Lepidoptera:Noctuidae)is a highly destructive pest of vegetables and field crops.Management of beet armyworm primarily relies on synthetic pesticides,which is threatening the b...The beet armyworm(BAW),Spodoptera exigua(Lepidoptera:Noctuidae)is a highly destructive pest of vegetables and field crops.Management of beet armyworm primarily relies on synthetic pesticides,which is threatening the beneficial community and environment.Most importantly,the BAW developed resistance to synthetic pesticides with making it difficult to manage.Therefore,alternative and environment-friendly pest management tactics are urgently required.The use of pesticidal plant extracts provides an effective way for a sustainable pest management program.To evaluate the use of pesticidal plant extracts against BAW,we selected six plant species(Lantana camara,Aloe vera,Azadirachta indica,Cymbopogon citratus,Nicotiana tabacum,and Ocimum basilicum)for initial screening experiment.Four out of six plant species such as A.indica,N.tabacum,C.citratus and O.basilicum showed promising mortality of more than 50%.Therefore,we selected these four plant extracts for the subsequent experiments.Through contact bioassay,A.indica showed high mortality 66.63%,followed by the N.tabacum 53.33%,at 10%w/v concentration.Similarly,N.tabacum showed the highest mortality rate,66%at 10%w/v concentration,followed by the A.indica 46%through feeding bioassay.Furthermore,the feeding deterrence assay showed that C.citratus had a high antifeedant index(−50)followed by A.indica(−39),and N.tabacum(−28).In living plant assay,the N.tabacum extract showed a low mean damage score 3.6 on living cotton plant followed by C.citratus 4.5 and A.indica 5.5.Hence,extracts of three plant species provided promising results against the BAW,which can minimize the use of synthetic chemicals,particularly for small landholding farmers.Further studies are also required to evaluate the effects of these plant extract against BAW on cotton plants under field conditions to optimize the further use.展开更多
Cellular growth dynamics and allelopathic activity in coffee cell cultures were examined as follows: First, we compared allelopathic activity of seven woody plant calli, Coffea canephora, Derris indica, Ficus carica L...Cellular growth dynamics and allelopathic activity in coffee cell cultures were examined as follows: First, we compared allelopathic activity of seven woody plant calli, Coffea canephora, Derris indica, Ficus carica L., Juniperus conferta, Prunus persica, Punica granatum, and Sonneratia ovata, using a modified “sandwich method bioassay” and found that coffee callus showed the strongest growth inhibition to lettuce seedling nearly 90% of hypocotyl and 96% of root. This coffee callus actively proliferated, with a 21-fold increase during five weeks of subculture, with a growth curve comprising two typical phases: a lag phase of 0 - 2 weeks of culture and an exponential phase of 3 - 5 weeks of culture. Allelopathic activity varied depending on the growth phase of the coffee callus. The strongest allelopathic activity was detected in 1 - 2-week-old callus showing nearly 100% inhibitory effect on lettuce seedling growth. As the allelopathic activity of coffee calli is extremely high, beyond the natural level in coffee leaves and green beans, we focused on analyzing the allelopathic activity of its aqueous extracts using high-performance liquid chromatography. Several prominent peaks, including two reference alkaloids, theobromine and caffeine, which are known allelochemicals in coffee plants, and three distinct unknown peaks were identified at 270 nm in coffee calli during the lag phase (1 - 2 weeks of culture). The higher value of the total phenolic content in the lag phase also suggested a key biosynthetic pathway in relation to the allelopathic activity of coffee callus will be activated in the lag phase.展开更多
文摘Allelopathy was defined in 1996 by IAS （international allelopathy society） as any process involving secondary metabolites produced by plant, algae, bacteria and fungi that influences the growth and development of agricultural and biological systems. Rice allelopathy against weeds was reported since 1989, which offers an integrated weed management with substantially reduced herbicide usage. Application of allelopathic rice cultivars is thought a resources conservation and environmental friendly way of weed bio-control, and could promote the sustainable development of agriculture. Screening or evaluating the allelopathic potential rice variety is the first step. In this paper, a new bioassay method was set up by the allelopathic potential of 9 rice lines on the target weed barnyardgrass （Echinochloa crusgalli）, and comparing with bioassay methods such as relay seeding in filter paper （RSF） and relay seeding in agar （RSA）. The results indicated that three methods had a same tendency in evaluating the allelopathic potential of rice; there existed a significant difference among different bioassay methods, and an interaction between bioassay methods and rice lines. The method of root exudates （RE） with the highest value and a correlation efficiency of 0.98 was considered as ideal bioassay method for evaluation of allelopathic potential.
文摘The beet armyworm(BAW),Spodoptera exigua(Lepidoptera:Noctuidae)is a highly destructive pest of vegetables and field crops.Management of beet armyworm primarily relies on synthetic pesticides,which is threatening the beneficial community and environment.Most importantly,the BAW developed resistance to synthetic pesticides with making it difficult to manage.Therefore,alternative and environment-friendly pest management tactics are urgently required.The use of pesticidal plant extracts provides an effective way for a sustainable pest management program.To evaluate the use of pesticidal plant extracts against BAW,we selected six plant species(Lantana camara,Aloe vera,Azadirachta indica,Cymbopogon citratus,Nicotiana tabacum,and Ocimum basilicum)for initial screening experiment.Four out of six plant species such as A.indica,N.tabacum,C.citratus and O.basilicum showed promising mortality of more than 50%.Therefore,we selected these four plant extracts for the subsequent experiments.Through contact bioassay,A.indica showed high mortality 66.63%,followed by the N.tabacum 53.33%,at 10%w/v concentration.Similarly,N.tabacum showed the highest mortality rate,66%at 10%w/v concentration,followed by the A.indica 46%through feeding bioassay.Furthermore,the feeding deterrence assay showed that C.citratus had a high antifeedant index(−50)followed by A.indica(−39),and N.tabacum(−28).In living plant assay,the N.tabacum extract showed a low mean damage score 3.6 on living cotton plant followed by C.citratus 4.5 and A.indica 5.5.Hence,extracts of three plant species provided promising results against the BAW,which can minimize the use of synthetic chemicals,particularly for small landholding farmers.Further studies are also required to evaluate the effects of these plant extract against BAW on cotton plants under field conditions to optimize the further use.
文摘Cellular growth dynamics and allelopathic activity in coffee cell cultures were examined as follows: First, we compared allelopathic activity of seven woody plant calli, Coffea canephora, Derris indica, Ficus carica L., Juniperus conferta, Prunus persica, Punica granatum, and Sonneratia ovata, using a modified “sandwich method bioassay” and found that coffee callus showed the strongest growth inhibition to lettuce seedling nearly 90% of hypocotyl and 96% of root. This coffee callus actively proliferated, with a 21-fold increase during five weeks of subculture, with a growth curve comprising two typical phases: a lag phase of 0 - 2 weeks of culture and an exponential phase of 3 - 5 weeks of culture. Allelopathic activity varied depending on the growth phase of the coffee callus. The strongest allelopathic activity was detected in 1 - 2-week-old callus showing nearly 100% inhibitory effect on lettuce seedling growth. As the allelopathic activity of coffee calli is extremely high, beyond the natural level in coffee leaves and green beans, we focused on analyzing the allelopathic activity of its aqueous extracts using high-performance liquid chromatography. Several prominent peaks, including two reference alkaloids, theobromine and caffeine, which are known allelochemicals in coffee plants, and three distinct unknown peaks were identified at 270 nm in coffee calli during the lag phase (1 - 2 weeks of culture). The higher value of the total phenolic content in the lag phase also suggested a key biosynthetic pathway in relation to the allelopathic activity of coffee callus will be activated in the lag phase.
