Creating a crop-heterogeneous system by intraspecific mixtures of different rice varieties can substantially reduce blast diseases. Such variety mixtures provide an ecological approach for effective disease control, m...Creating a crop-heterogeneous system by intraspecific mixtures of different rice varieties can substantially reduce blast diseases. Such variety mixtures provide an ecological approach for effective disease control, maintaining high yields with the minimum fungicide applications. Whether such an approach is universally applicable for random rice variety combinations and what is the variation pattern of the diseases under intercropping still remains unclear. We conducted two-year large-scale field experiments involving 47 rice varieties/lines and 98 variety-combinations to compare the occurrence of rice blast in monoculture and intercropping plots at multiple sites. In the experiments, the plant height of the selected tradi- tional varieties was about 30 cm taller, and their life cycle was 10 days longer, than that of the improved rice varieties. The monoculture included either traditional or modern rice varieties grown in separate plots. The intercropping included both traditional and modern rice varieties planted together in the same plots. Results from the field experiments under natural disease conditions demonstrated significant reduction for rice blast disease in intercropping plots, compared with that in monoculture plots. For traditional varieties, the average blast incidence reduced from -26% in monoculture to -10% in intercropping, and the disease severity reduced from -17 in monoculture to -5 in intercropping. For modern varieties, the average blast incidence reduced from -19% in monoculture to -10% in intercropping, and the severity from -10 in mono- culture to -4 in intercropping. Traditional rice varieties （-72%） had a much greater increase in the efficiency of disease control than modern varieties （-60%）. In addition, substantially lower values of variance in the blast incidence and severity was detected among the variety combinations in intercropping plots than in monoculture plots. Based on these results, we conclude that the intercropping or mixture of rice varieties greatly reduces the occurrence and variation of rice blast disease in particular variety combinations, which makes the intercropping system more stable and consistent for disease suppression on a large scale of rice cultivation.展开更多
Eighty-five rice(Oryza sativa L.)varieties,including 82 rice landraces collected from 17villages in Yunnan Province of China and three standard varieties representing typical Indica and Japonica ecotypes,were studied ...Eighty-five rice(Oryza sativa L.)varieties,including 82 rice landraces collected from 17villages in Yunnan Province of China and three standard varieties representing typical Indica and Japonica ecotypes,were studied using simple sequence repeat(SSR)markers to estimate their genetic diversity for the purpose of strategic conservation.Nineteen selected SSR primer pairs amplified a total of 83 SSR alleles,with molecular weight ranging from 100 to 500 bp,from the 85 rice varieties.An UPGMA dendrogram based on the cluster analysis of genetic similarity of the SSR alleles showed a significant genetic variation among the included rice varieties,with the similarity coefficients varying between 0.152 and 0.900.However,genetic diversity of the rice varieties collected from Yunnan was unevenly distributed over their geographical locations.Two distinct groups were identified from the cluster analysis of the 85rice varieties at the similarity coefficient level of 0.152,with one group that included almost all accessions of Indica ecotype and another group that contained all accessions of Japonica ecotype.Varieties that shared the same names but collected from different villages did not always show a close genetic relationship,indicating misidentification of some varieties by local farmers.It is concluded from this study that conservation of genetic diversity in rice landraces is urgently necessary in Yunnan,given their high level of diversity,but an appropriate strategy needs to be followed to guarantee the effectiveness of conservation activities.Properly selected SSR primer pairs might provide an ideal method for identifying Indica and Japonica ecotypes for rice conservation and breeding programs.展开更多
The aldehyde dehydrogenase （ALDH） superfamily of NAD（P）-dependent enzymes, in general, oxidize a wide range of endogenous and exogenous aliphatic and aromatic aldehydes to their corresponding carboxylic acids and ...The aldehyde dehydrogenase （ALDH） superfamily of NAD（P）-dependent enzymes, in general, oxidize a wide range of endogenous and exogenous aliphatic and aromatic aldehydes to their corresponding carboxylic acids and play an essential role in detoxification of reactive oxygen species （ROS） accumulated under the stressed conditions. In order to identify genes required for the stresses responses in the grass crop Oryza sativa, a homologue of ALDH gene （OsALDH22） was isolated and characterized. OsALDH22 is conserved in eukaryotes, shares high homology with the orthologs from aldehyde dehydrogenase subfamily ALDH22. The OsALDH22 encodes a protein of 597 amino acids that in plants exhibit high identity with the orthologs from Zea mays, Sorghum bicolor, Hordeum vulgare and Arabidopsis thaliana, respectively, and the conserved amino acid characteristics for ALDHs are present, including the possible NAD~ binding site （F-V-G-S- P-G-V-G）, the catalytic site （V-T-L-E-L-G-G-K） and the Cys active site. Semi-quantitative PCR and real-time PCR analysis indicates that OsALDH22 is expressed differentially in different tissues. Various elevated levels of OsALDH22 expression have been detected when the seedlings exposed to abiotic stresses including dehydration, high salinity and abscisic acid （ABA）. Transgenic rice plants overexpressing OsALDH22 show elevated stresses tolerance. On the contrary, down- 0 regulation of OsALDH22 in the RNA interference （RNAi） repression transgenic lines manifests declined stresses tolerance.展开更多
Vernalization, the process of a long exposure to low temperature to induce flowering in plants, is essential for plants to adapt to cold winters. The presence of vernalization genes Vrn-A1, -B1, and -D1 in four corner...Vernalization, the process of a long exposure to low temperature to induce flowering in plants, is essential for plants to adapt to cold winters. The presence of vernalization genes Vrn-A1, -B1, and -D1 in four cornerstone breeding parents of wheat in China （Funo, Mentana, Yanda 1817, and Bima 4） and 322 derivative varieties （mostly winter wheat） from these parents were determined using PCR based molecular method. The frequencies of the VRN-1 genes in these derivative varieties were in order of Vrn-Dl（67.1%）〉 Vrn-Bl（19.6%）〉 Vrn-Al（5.3%）, which are similar as the former conclusion that Vrn-D1 is associated with the latest heading time, Vrn-A1 the earliest, and Vrn-B1 intermediate values. The frequencies of Vrn-Al and Vrn-B1 loci in the derivative varieties from winter wheat zones were higher than that from spring winter zones. Based on the wheat breeding history in China and the fact of non-random distribution of Vrn-A1 and Vrn-B1 in the derivative varieties from the four parents, there could be a strong selective effect on VRN-1 genes in different regions where the derivative varieties were cultivated.展开更多
基金funded by the National Basic Research Program of China (2011CB100401)
文摘Creating a crop-heterogeneous system by intraspecific mixtures of different rice varieties can substantially reduce blast diseases. Such variety mixtures provide an ecological approach for effective disease control, maintaining high yields with the minimum fungicide applications. Whether such an approach is universally applicable for random rice variety combinations and what is the variation pattern of the diseases under intercropping still remains unclear. We conducted two-year large-scale field experiments involving 47 rice varieties/lines and 98 variety-combinations to compare the occurrence of rice blast in monoculture and intercropping plots at multiple sites. In the experiments, the plant height of the selected tradi- tional varieties was about 30 cm taller, and their life cycle was 10 days longer, than that of the improved rice varieties. The monoculture included either traditional or modern rice varieties grown in separate plots. The intercropping included both traditional and modern rice varieties planted together in the same plots. Results from the field experiments under natural disease conditions demonstrated significant reduction for rice blast disease in intercropping plots, compared with that in monoculture plots. For traditional varieties, the average blast incidence reduced from -26% in monoculture to -10% in intercropping, and the disease severity reduced from -17 in monoculture to -5 in intercropping. For modern varieties, the average blast incidence reduced from -19% in monoculture to -10% in intercropping, and the severity from -10 in mono- culture to -4 in intercropping. Traditional rice varieties （-72%） had a much greater increase in the efficiency of disease control than modern varieties （-60%）. In addition, substantially lower values of variance in the blast incidence and severity was detected among the variety combinations in intercropping plots than in monoculture plots. Based on these results, we conclude that the intercropping or mixture of rice varieties greatly reduces the occurrence and variation of rice blast disease in particular variety combinations, which makes the intercropping system more stable and consistent for disease suppression on a large scale of rice cultivation.
文摘Eighty-five rice(Oryza sativa L.)varieties,including 82 rice landraces collected from 17villages in Yunnan Province of China and three standard varieties representing typical Indica and Japonica ecotypes,were studied using simple sequence repeat(SSR)markers to estimate their genetic diversity for the purpose of strategic conservation.Nineteen selected SSR primer pairs amplified a total of 83 SSR alleles,with molecular weight ranging from 100 to 500 bp,from the 85 rice varieties.An UPGMA dendrogram based on the cluster analysis of genetic similarity of the SSR alleles showed a significant genetic variation among the included rice varieties,with the similarity coefficients varying between 0.152 and 0.900.However,genetic diversity of the rice varieties collected from Yunnan was unevenly distributed over their geographical locations.Two distinct groups were identified from the cluster analysis of the 85rice varieties at the similarity coefficient level of 0.152,with one group that included almost all accessions of Indica ecotype and another group that contained all accessions of Japonica ecotype.Varieties that shared the same names but collected from different villages did not always show a close genetic relationship,indicating misidentification of some varieties by local farmers.It is concluded from this study that conservation of genetic diversity in rice landraces is urgently necessary in Yunnan,given their high level of diversity,but an appropriate strategy needs to be followed to guarantee the effectiveness of conservation activities.Properly selected SSR primer pairs might provide an ideal method for identifying Indica and Japonica ecotypes for rice conservation and breeding programs.
基金the National 973 Program of China (2011CB100401)the Chongqing Municipal Science and Technology Research Project of China (2010AA1019)+1 种基金the National Science and Technology Key Projects of China (2009ZX08001-011B and 2009ZX08009-072B)the National Science Fund for Distinguished Young Scholars of China (30825030)
文摘The aldehyde dehydrogenase （ALDH） superfamily of NAD（P）-dependent enzymes, in general, oxidize a wide range of endogenous and exogenous aliphatic and aromatic aldehydes to their corresponding carboxylic acids and play an essential role in detoxification of reactive oxygen species （ROS） accumulated under the stressed conditions. In order to identify genes required for the stresses responses in the grass crop Oryza sativa, a homologue of ALDH gene （OsALDH22） was isolated and characterized. OsALDH22 is conserved in eukaryotes, shares high homology with the orthologs from aldehyde dehydrogenase subfamily ALDH22. The OsALDH22 encodes a protein of 597 amino acids that in plants exhibit high identity with the orthologs from Zea mays, Sorghum bicolor, Hordeum vulgare and Arabidopsis thaliana, respectively, and the conserved amino acid characteristics for ALDHs are present, including the possible NAD~ binding site （F-V-G-S- P-G-V-G）, the catalytic site （V-T-L-E-L-G-G-K） and the Cys active site. Semi-quantitative PCR and real-time PCR analysis indicates that OsALDH22 is expressed differentially in different tissues. Various elevated levels of OsALDH22 expression have been detected when the seedlings exposed to abiotic stresses including dehydration, high salinity and abscisic acid （ABA）. Transgenic rice plants overexpressing OsALDH22 show elevated stresses tolerance. On the contrary, down- 0 regulation of OsALDH22 in the RNA interference （RNAi） repression transgenic lines manifests declined stresses tolerance.
基金supported by the National 973 Program of China(2006CB101700)the National 863 Program of China(2006AA10Z1C6)+1 种基金the National Natural Science Foundation of China(30771338,30700495)the Science and Technology Department of SichuanProvince,China(09ZQ026-086)
文摘Vernalization, the process of a long exposure to low temperature to induce flowering in plants, is essential for plants to adapt to cold winters. The presence of vernalization genes Vrn-A1, -B1, and -D1 in four cornerstone breeding parents of wheat in China （Funo, Mentana, Yanda 1817, and Bima 4） and 322 derivative varieties （mostly winter wheat） from these parents were determined using PCR based molecular method. The frequencies of the VRN-1 genes in these derivative varieties were in order of Vrn-Dl（67.1%）〉 Vrn-Bl（19.6%）〉 Vrn-Al（5.3%）, which are similar as the former conclusion that Vrn-D1 is associated with the latest heading time, Vrn-A1 the earliest, and Vrn-B1 intermediate values. The frequencies of Vrn-Al and Vrn-B1 loci in the derivative varieties from winter wheat zones were higher than that from spring winter zones. Based on the wheat breeding history in China and the fact of non-random distribution of Vrn-A1 and Vrn-B1 in the derivative varieties from the four parents, there could be a strong selective effect on VRN-1 genes in different regions where the derivative varieties were cultivated.
