Marker-assisted selection, QTLs and contig lines for improving downy mildew resistance of pearl millet hybrids. Final Technical Report.
Abstract
This project had as its primary purpose increasing the yield and yield stability of pearl millet hybrids by improving their resistance to downy mildew (DM) disease. It was intended to identify previously unidentified quantitative trait loci (QTLs) (equivalent to host plant resistance genes) for pearl millet DM resistance, and make these available to plant breeders in arid and semi-arid regions of India where hybrid pearl millets are grown. It was further intended to familiarize a wider range of breeders in these areas with the utility of marker-assisted selection (MAS) to improve disease resistance of economically important hybrid parental lines developed in their own breeding programmes. Additional host plant resistances to downy mildew were identified by screening mapping populations against a diverse range of pathogen isolates from pearl millet producing regions of Africa and Asia - the resulting phenotypic data were combined with marker genotype data to map quantitative trait loci (QTLs) contributing to disease reaction against each pathogen isolate. Individually, or in combination with a few others, such QTLs accounted for as much as 70% of the observed phenotypic variation for disease reaction when a given pathogen isolate was used to screen a particular pearl millet mapping population. Transfer of several resistance QTLs from mapped donor parents P 7-3 and ICMP 85410 to the elite genetic background of early dwarf maintainer line 843B was completed, and evaluation of the hybrid performance of these (and their male-sterile line counterparts) was initiated. Based on these initial results it appears it will be possible, in some but not all cases, to introduce QTLs for improved disease resistance into such elite hybrid parental lines without adversely affecting the performance of their hybrids (as might occur if there were negative linkage drag effects due to linkage between genes controlling resistance and those controlling other characters of economic importance). Contiguous segmental substitution line set development of segments of ICMP85410 in the 843B approached completion. It has allowed identification of genomic regions associated with male fertility restoration ability for the A1 cytoplasmic-genetic male-sterility system, as well as those associated with panicle length and flowering time. Products of this research stream began to reach private- and public-sector pearl millet breeders in India during the course of this project, and should make it to farmers' fields in India in a big way over the next five years, directly contributing to DFID's development goal of improving production of target crops on impoverished soils in semi-arid areas by selection and genetic enhancement of cultivars.
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