Advanced Molecular Breeding for Yield

Abstract

AbstractImprovement in crop yields in Brassica juncea has been stagnating for some time, a trend that is likely to exacerbate further due to the effects of various biotic and abiotic stresses like insects or diseases, drought, submergence, salinity and high temperature. The crucial increase in the crop production should necessarily come from higher yields, since there is little scope for expanding the agricultural land base. These factors must be addressed directly in targeted approaches for improvement in yield. Yield influencing traits with a large genetic component and direct correlation with yield can be considered suitable as selection criteria. Different morphological characters like number of pods per plant, number of seeds per pod and seed weight along with flowering time fulfill these criteria, and have therefore been the subject of genetic analysis by molecular mapping. The genetic dissection of principal yield components, documentation of genes and quantitative trait loci (QTLs) associated with various trait phenotypes in B. juncea have been undertaken in several studies which were based on a wide array of molecular markers including restriction fragment length polymorphism, amplified fragment length polymorphism, intron polymorphism, simple sequence repeats, etc. A few of these studies have also indicated that the A sub genome has played a major role compared to the B sub genome in the process of domestication of B. juncea as an oilseed crop. Moreover, it also appears that rigorous selection procedures were in practice for the selection of superior alleles during the course of domestication of lines belonging to the Indian germplasm as compared to lines of the exotic gene pool. However, genes underlying the QTLs for yield and most of the yield-related traits have still not been identified. Recent developments in the sequencing technologies are anticipated to further accelerate the discovery of the genomic regions/QTLs associated with yield and related traits. This chapter provides a detailed review on molecular mapping approaches for dissection of the genetic bases of yield in B. juncea.Keywords Brassica juncea Genetic mapQuantitative traitsYield-related traitsMeta-analysisEpistasis