Use of molecular markers to improve terminal drought tolerance in pearl millet. Final Technical Report.
Abstract
The purpose of the project was to identify and characterise new QTLs for terminal drought tolerance in pearl millet (by studying a mapping population from a cross between ICMB 841x 843B) and to transfer those identified in an earlier project (R 6451) into the agronomically elite pollinator H 77/833-2 using marker-assisted backcrossing. Three new QTLs for terminal drought tolerance (in addition to one identified on LG 2 by studying H 77/833-2 x PRLT 2/98-33 cross in R 6445) were identified using ICMB 841 x 843B. These QTLs were also characterised for their effects on agronomic traits such as grain and stover yield per se in terminal drought stress environments and for the putative physiological mechanisms associated with them. These QTLs contributed to increased grain yield in terminal drought stress environments either by their effects on increased harvest index or biomass yield or both. QTLs for physiological mechanisms underlying drought tolerance such as increased relative water content, delayed leaf rolling, osmotic adjustment and early flowering comapped to these QTLs indicating the role of these processes in contributing to increased grain and stover yield under terminal drought stress conditions. QTLs for morphological traits (such as plant height, panicle characteristics etc.) and for yield under non-drought conditions were also identified. The QTL for terminal drought tolerance identified on LG 2 by studying the H 77/833-2 x PRLT 2/98- 33 mapping population was transferred to elite parental line H 77/833-2 using marker assisted back crossing. NILs for individual QTL so developed were tested for their response to drought in a number of terminal drought stress environments to revalidate effect of this QTL in a range of environments. NIls were also tested in the genetic background of several different female parents to understand QTL x genetic backgrounds effects. This QTL for terminal drought tolerance was found to have a positive effect in most terminal drought stress environments without any significant effect on yield in the irrigated control environment. In some situations, significant QTL x genetic background interactions effects were observed. QTL x genotype interaction was mainly associated with plant size: high tillering backgrounds leading to large plant size were found to negate the effect of QTL. In addition to marker assisted back crossing, this QTL was also transferred into a more heterogeneous genetic background by developing top cross pollinator populations (TCPs). TCPs so developed were again tested in different water environments and genetic backgrounds and showed superior performance in terminal drought stress environments. During the project period, other QTLs for terminal drought tolerance identified by studying ICM841 x 863B mapping family were also transferred to the background of sensitive parent using marker assisted backcrossing. NILs for these individual QTLs are now ready for evaluation. Study of these NILs would lead towards detailed characterisation of these QTLs for their usability in different water stress environments and genetic backgrounds. These QTL NILs together with those developed for other QTLs in other DFID funded projects could be utilised to accumulate useful QTLs in elite pearl millet cultivars with wider adaptability, yielding, and resistance to diseases.
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