The backcross(BC) breeding strategy has been increasingly used for developing high yielding varieties with improved abiotic stress tolerances in rice. In this study, 189Huang-Hua-Zhan(HHZ) introgression lines(ILs) dev...The backcross(BC) breeding strategy has been increasingly used for developing high yielding varieties with improved abiotic stress tolerances in rice. In this study, 189Huang-Hua-Zhan(HHZ) introgression lines(ILs) developed from three different selection schemes were evaluated for yield related traits under drought stress and non-stress conditions in the target and off-season winter nursery environments to assess the selection efficiency of BC breeding for improving different complex traits, and led us to five important results. The first result indicated that the primary target traits should be selected first in the target environments(TEs) in order to achieve the maximum genetic gain. Secondly, BC breeding for drought tolerance(DT) in rice was almost equally effective by strong phenotypic selection in the main target environments and in the winter-season of Hainan.Thirdly, exploiting genetic diversity in the subspecific gene pools is of great importance for future genetic improvement of complex traits in rice. Fourthly, considerable genetic gain can be effectively achieved by selection for secondary target traits among the ILs with the primary traits. Finally, the developed ILs provide useful materials for future genetic/genomic dissection and molecular breeding of complex traits.展开更多
The selection of superior genotypes based on the simultaneous response to several characteristics of agronomic importance is a key strategy to overcome the scarcity of available varieties of papaya. This study aimed t...The selection of superior genotypes based on the simultaneous response to several characteristics of agronomic importance is a key strategy to overcome the scarcity of available varieties of papaya. This study aimed to apply the combined selection by using distinct selection indexes based on both the genetic values obtained by the REML/BLUP methodology and the real measured values to select agronomically superior genotypes of papaya within backcross progenies. The combined selection was carried out based on genetic and phenotypic values, original and standardized, multiplied by the agronomic weights. The results of the analysis of genetic parameters indicate that the evaluated progenies have expressive genetic variability for the considered traits, and that there are real possibilities of genetic progress with the selection. Among the analyzed indexes, the one based on standardized genetic value presented greater consistency in the ranking of genetic material, demonstrating the advantage of data standardization. Five progenies belonging to the BC1 generation, and five to the BC3 generation were selected using this index. A total of 27 plants ag-ronomically superior were selected within the top five progenies and recommended for generation advance, 23 being selected by combined selection and 4 using the direct selection for the four mainly characters in papaya breeding program: production, pulp and fruit firmness and soluble solids. Beyond the selection of superior genotypes for the development of future inbred lines, this study also allowed defining the best strategy to apply the combined selection in papaya using pre-dicted breeding values obtained by BLUP. This strategy may allow higher accuracy in the selection process, thus increasing the chances of success of the breeding programs.展开更多
Cassava mosaic disease （CMD）, the most important disease of cassava （Manihot esculenta Crantz） is a potential threat to Africa＇s cassava production. The disease is embedded in most landraces resulting in low yiel...Cassava mosaic disease （CMD）, the most important disease of cassava （Manihot esculenta Crantz） is a potential threat to Africa＇s cassava production. The disease is embedded in most landraces resulting in low yields. Host plant resistance has been found to be the best control strategy. A breeding programme using genetic hybridisation and Marker Assisted Selection was initiated in 2007 to improve the resistance levels of farmer-preferred landraces and reduce the long breeding cycle for developing improved cassava varieties. Thirty farmer-preferred landraces were selected and crossed with a high yielding and mosaic resistant cultivar （TMEI l） from International Institute of Tropical Agriculture （IITA）. The resultant progenies found to have a reasonable level of resistance （score, 1-3） to the CMD were AW 18, 273 Nyamebekyere, NK 43, AW 3, NK 26, K 25, Dabodabo, Ahwengyankwa, 674 Debor, Degarti, Agric Bankye, and NK 57. These resultant progenies were backcrossed to the resistant cultivar. The backcross one （BC l） progenies totaling 224 were screened with molecular markers that are associated to the CMD 2 gene. De-oxyribonucleic Acid （DNA） was extracted from leaves of the 224 BC1 progenies and 13 parents. Two Simple Sequence Repeats （SSR） markers （SSY28 and NSl58） and one Sequenced Characterized Amplified Region （SCAR） marker RME1, were used to screen and select for the resistant BC l progenies. Marker Assisted Selection （MAS） revealed that 82% of the genotypes had at least a marker allele for the CMD2 gene, indicating resistance. The study further revealed that by using MAS, the breeding cycle of cassava in the generation of varieties could be reduced from 8 years to 2 years. The resistant genotypes identified will be evaluated for yield and starch cooking quality in future breeding work.展开更多
Further improvement of rice productivity remains a challenge. Breeding is perceived as an important option to increase rice yield. However, the genetic progress of grain yield in most rice breeding programs was slow i...Further improvement of rice productivity remains a challenge. Breeding is perceived as an important option to increase rice yield. However, the genetic progress of grain yield in most rice breeding programs was slow in the last decades. Although great progress in rice genomics and molecular biology has been achieved, the effect of such technological innovations on rice breeding is far small. Marker-assisted selection （MAS） for a few target quantitative trait loci （QTLs） has significant effects in improving qualitative traits, such as disease resistance. The success of MAS has therefore motivated breeders to identify and use major QTLs for yield and yield component traits. In this review, we summarized the recent methods in QTL identification, including novel statistical methods for linkage and association mapping, special population types, and whole-genome sequencing. We reviewed the successful application of marker-assisted gene introgression and gene pyramiding to improve grain yield and discussed the design of efficient MAS schemes to further increase the success rate of breeding programs. The use of well-characterized major QTLs through introgression and gene pyramiding is proven effective in improving grain yield, particularly yield under abiotic stress. Major QTLs that are stable across genetic background and growing environments are often found in less adapted germplasms, such as landraces and wild relatives. Advanced backcross QTL analysis and introgression lines, which integrate QTL discovery and utilization, are important methods for exploiting major QTLs contained in such germplasms. Next-generation sequencing substantially increases mapping resolution and accelerates the identification of casual genes underlying major QTLs. Practical guidelines derived from theoretical and empirical studies are given to guide the design of efficient marker-assisted gene introgression and pyramiding schemes.展开更多
基金funded by the National High Technology Research and Development Program of China (2012AA101101) from the Ministry of Science and Technology of Chinathe National Science Foundation Project (30570996)+1 种基金the Program of Introducing International Super Agricultural Science and Technology (#2011-G2B) from the Ministry of Agriculture of Chinathe Bill & Melinda Gates Foundation Project (OPP51587)
文摘The backcross(BC) breeding strategy has been increasingly used for developing high yielding varieties with improved abiotic stress tolerances in rice. In this study, 189Huang-Hua-Zhan(HHZ) introgression lines(ILs) developed from three different selection schemes were evaluated for yield related traits under drought stress and non-stress conditions in the target and off-season winter nursery environments to assess the selection efficiency of BC breeding for improving different complex traits, and led us to five important results. The first result indicated that the primary target traits should be selected first in the target environments(TEs) in order to achieve the maximum genetic gain. Secondly, BC breeding for drought tolerance(DT) in rice was almost equally effective by strong phenotypic selection in the main target environments and in the winter-season of Hainan.Thirdly, exploiting genetic diversity in the subspecific gene pools is of great importance for future genetic improvement of complex traits in rice. Fourthly, considerable genetic gain can be effectively achieved by selection for secondary target traits among the ILs with the primary traits. Finally, the developed ILs provide useful materials for future genetic/genomic dissection and molecular breeding of complex traits.
基金the Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro(FAPERJ)for providing the Master’s scholarshipthe Empresa Caliman Agrícola S/A(Caliman)for the financial and logistical support.
文摘The selection of superior genotypes based on the simultaneous response to several characteristics of agronomic importance is a key strategy to overcome the scarcity of available varieties of papaya. This study aimed to apply the combined selection by using distinct selection indexes based on both the genetic values obtained by the REML/BLUP methodology and the real measured values to select agronomically superior genotypes of papaya within backcross progenies. The combined selection was carried out based on genetic and phenotypic values, original and standardized, multiplied by the agronomic weights. The results of the analysis of genetic parameters indicate that the evaluated progenies have expressive genetic variability for the considered traits, and that there are real possibilities of genetic progress with the selection. Among the analyzed indexes, the one based on standardized genetic value presented greater consistency in the ranking of genetic material, demonstrating the advantage of data standardization. Five progenies belonging to the BC1 generation, and five to the BC3 generation were selected using this index. A total of 27 plants ag-ronomically superior were selected within the top five progenies and recommended for generation advance, 23 being selected by combined selection and 4 using the direct selection for the four mainly characters in papaya breeding program: production, pulp and fruit firmness and soluble solids. Beyond the selection of superior genotypes for the development of future inbred lines, this study also allowed defining the best strategy to apply the combined selection in papaya using pre-dicted breeding values obtained by BLUP. This strategy may allow higher accuracy in the selection process, thus increasing the chances of success of the breeding programs.
文摘Cassava mosaic disease （CMD）, the most important disease of cassava （Manihot esculenta Crantz） is a potential threat to Africa＇s cassava production. The disease is embedded in most landraces resulting in low yields. Host plant resistance has been found to be the best control strategy. A breeding programme using genetic hybridisation and Marker Assisted Selection was initiated in 2007 to improve the resistance levels of farmer-preferred landraces and reduce the long breeding cycle for developing improved cassava varieties. Thirty farmer-preferred landraces were selected and crossed with a high yielding and mosaic resistant cultivar （TMEI l） from International Institute of Tropical Agriculture （IITA）. The resultant progenies found to have a reasonable level of resistance （score, 1-3） to the CMD were AW 18, 273 Nyamebekyere, NK 43, AW 3, NK 26, K 25, Dabodabo, Ahwengyankwa, 674 Debor, Degarti, Agric Bankye, and NK 57. These resultant progenies were backcrossed to the resistant cultivar. The backcross one （BC l） progenies totaling 224 were screened with molecular markers that are associated to the CMD 2 gene. De-oxyribonucleic Acid （DNA） was extracted from leaves of the 224 BC1 progenies and 13 parents. Two Simple Sequence Repeats （SSR） markers （SSY28 and NSl58） and one Sequenced Characterized Amplified Region （SCAR） marker RME1, were used to screen and select for the resistant BC l progenies. Marker Assisted Selection （MAS） revealed that 82% of the genotypes had at least a marker allele for the CMD2 gene, indicating resistance. The study further revealed that by using MAS, the breeding cycle of cassava in the generation of varieties could be reduced from 8 years to 2 years. The resistant genotypes identified will be evaluated for yield and starch cooking quality in future breeding work.
基金supported by the National Natural Science Foundation of China(Grant Nos.31221004 and 31271700)National Basic Research Program of China(Grant No.2013CBA01405)the Chinese 863 Program(Grant No.2012AA10A302)
文摘Further improvement of rice productivity remains a challenge. Breeding is perceived as an important option to increase rice yield. However, the genetic progress of grain yield in most rice breeding programs was slow in the last decades. Although great progress in rice genomics and molecular biology has been achieved, the effect of such technological innovations on rice breeding is far small. Marker-assisted selection （MAS） for a few target quantitative trait loci （QTLs） has significant effects in improving qualitative traits, such as disease resistance. The success of MAS has therefore motivated breeders to identify and use major QTLs for yield and yield component traits. In this review, we summarized the recent methods in QTL identification, including novel statistical methods for linkage and association mapping, special population types, and whole-genome sequencing. We reviewed the successful application of marker-assisted gene introgression and gene pyramiding to improve grain yield and discussed the design of efficient MAS schemes to further increase the success rate of breeding programs. The use of well-characterized major QTLs through introgression and gene pyramiding is proven effective in improving grain yield, particularly yield under abiotic stress. Major QTLs that are stable across genetic background and growing environments are often found in less adapted germplasms, such as landraces and wild relatives. Advanced backcross QTL analysis and introgression lines, which integrate QTL discovery and utilization, are important methods for exploiting major QTLs contained in such germplasms. Next-generation sequencing substantially increases mapping resolution and accelerates the identification of casual genes underlying major QTLs. Practical guidelines derived from theoretical and empirical studies are given to guide the design of efficient marker-assisted gene introgression and pyramiding schemes.
