Posts Tagged ‘Hybrid’

Does low yield heterosis limit commercial hybrids in wheat?

Posted by Carelia Juarez on , in Journal Articles

Published in African Journal of Agricultural Research 8 (50) : 6663-6669, 2013

Sharma, R.K.

Heterosis has contributed to productivity gains in several crops like maize, rice, sorghum, cotton etc. Wheat breeders have largely been unsuccessful to take advantage from this technology at commercial level. Lack of commercial level yield heterosis is regarded as a major reason for this failure as compared to other technical barriers like difficult pollination control and seed production. The allopolyploidy nature of wheat endows even wheat purelines with a fixed intergenomic heterosis which perhaps is the foremost reason for lack of classical yield heterosis in wheat. The coming together of three diverse but functionally similar genomes causes differential gene expression among several other outcomes and leads to a diploid behaving self-sustaining intergenomic hybrid. A long history of highly successful pureline breeding and shortage of nicking parents are other two reasons responsible for failure to realize commercial level heterosis in wheat. Molecular biology tools now make it possible to dissect the phenomenon of heterosis into detectable Mendelian factors to tailor nicking parents to develop commercially sustainable wheat hybrids. This review probes the reasons for the absence of commercial-scale heterosis in wheat.

Performance prediction of F1 hybrids between recombinant inbred lines derived from two elite maize inbred lines

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics 126 (1) : 189-201, 2013

Tingting Guo, Huihui Li, Jianbing Yan, Jihua Tang, Jiansheng Li, Zhiwu Zhang, Luyan Zhang and Jiankang Wang

Selection of recombinant inbred lines (RILs) from elite hybrids is a key method in maize breeding especially in developing countries. The RILs are normally derived by repeated self-pollination and selection. In this study, we first investigated the accuracy of different models in predicting the performance of F1 hybrids between RILs derived from two elite maize inbred lines Zong3 and 87-1, and then compared these models through simulation using a wider range of genetic models. Results indicated that appropriate prediction models depended on genetic architecture, e.g., combined model using breeding value and genome-wide prediction (BV+GWP) has the highest prediction accuracy for high VD/VA ratio (>0.5) traits. Theoretical studies demonstrated that different components of genetic variance were captured by different prediction models, which in turn explained the accuracy of these models in predicting the F1 hybrid performance. Based on genome-wide prediction model (GWP), 114 untested F1 hybrids possibly having higher grain yield than the original F1 hybrid Yuyu22 (the single cross between Zong3 and 87-1) have been identified and recommended for further field test.

Strategies to subdivide a target population of environments: Results from the CIMMYT-led maize hybrid testing programs in Africa

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Science 52 (5) : 2143-2152, 2012

Vanessa S. Windhausen, Silke Wagener, Cosmos Magorokosho, Dan Makumbi, Bindiganavile Vivek, Hans-Peter Piepho, Albrecht E. Melchinger and Gary N. Atlin

To develop stable and high-yielding maize (Zea mays L.) hybrids for a diverse target population of environments (TPE), breeders have to decide whether greater gains result from selection across the undivided TPE or within more homogeneous subregions. Currently, CIMMYT subdivides the TPE in eastern and southern Africa into climatic and geographic subregions. To study the extent of specific adaptation to these subregions and to determine whether selection within subregions results in greater gains than selection across the undivided TPE, yield data of 448 maize hybrids evaluated in 513 trials across 17 countries from 2001 to 2009 were used. The trials were grouped according to five subdivision systems into climate, altitude, geographic, country, and yield-level subregions. For the first four subdivision systems, genotype × subregion interaction was low, suggesting broad adaptation of maize hybrids across eastern and southern Africa. In contrast, genotype × yield-level interactions and moderate genotypic correlations between low- and high-yielding subregions were observed. Therefore, hybrid means should be estimated by stratifying the TPE considering the yield-level effect as fixed and appropriately weighting information from both subregions. This strategy was at least 10% better in terms of predicted gains than direct selection using only data from the low- or high-yielding subregion and should facilitate the identification of hybrids that perform well in both subregions.