Introgression and Exploitation of QTL for Yield and Yield Components from Related Wild Species in Rice Cultivars

Abstract

Green revolution led to the narrowing of the genetic base of cultivated rice gene pool. Genetic diversity is the prerequisite for increasing yield and for stabilizing production under series of biotic and abiotic stresses. The wild Oryza species comprising AA, BB, CC, BBCC, CCDD, EE, FF, GG, HH, and JJ genomes are the important reservoir of useful genes. The wild relatives of crop species with hidden potential for useful variability are, however, phenotypically less desirable than the modern cultivars in their overall appearance. They have been utilized extensively for introgression of major genes for disease and insect resistance, but their utilization in enhancing yield and yield-related traits of modern cultivars has remained limited. The related wild species Oryza rufipogon (AA genome) has been utilized widely for transferring yield and yield-related traits to the elite rice cultivars followed by reports on O. glaberrima, O. minuta, O. nivara, and O. glumaepatula. The availability of advance molecular breeding techniques has enabled the use of alien species with minimum linkage drag. Yield QTLs have been identified on almost all the rice chromosomes though the QTL clusters are confined to only four (1, 2, 3, and 4) chromosomes. Some of the component traits of yield have higher heritability and correlation among themselves. This provides an opportunity for their simultaneous improvement for more than one trait using marker-assisted selection. Many QTLs from different wild species are mapped to the identical chromosomal regions, thus giving an idea of orthologous yield QTLs across the species and populations. This chapter deals with the utilization of wild species for introgression of QTLs for yield and yield-related traits for the improvement of rice productivity.