Fine mapping of QTL on chromosome 9 for drought tolerance in maize
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Drought is considered as one of the major limiting factors in sustainable maize production all over the world as it causes yield reduction by an average of 15% to 20%. Maize is generally grown in Kharif season but spring maize is now coming up in India. However, the water requirement is very high but farmers are reluctant to see the long term effect of maize cultivation during spring season. To meet the growing demand of water during spring season, enhancement of maize yield can be achieved by developing water efficient maize hybrids. The objective of the study was to identify and to transfer QTL associated with drought tolerance into spring maize inbreds through marker assisted backcross breeding (MABB). A total of 135 F8 recombinant inbred lines (RILs) from the cross between CM123 as the susceptible (female) parent and CM140 as the tolerant (male) parent along with parents were evaluated under control and drought stress conditions for two consecutive seasons. The QTL on chromosome 1, 3, 4, 6, 7 and 9 were identified for drought tolerance under both stress and control conditions. The present study focused on fine mapping of QTL for number of kernel per ear (qKPE) present on chromosome 9 (bnlg1401-umc1634) explaining phenotypic variance of 23.14% under stressed environment. This region was narrow down by designing 50 new SSR markers between the bracketed QTL (qKPE). Seventeen SSR markers showed the polymorphism between CM123 and CM140. These markers along-with previous mapped markers were employed on RIL population. The QTL analysis narrowed down the genetic distance to 3.8 cM from 11.5 cM and physical distance to 691 kb from earlier distance of 15 Mb flanked by two new SSR markers viz. PAU_1143 and PAU_1137. The qKPE is also introgressed through MABB into two spring maize inbreds LM23 and LM24 of hybrid PMH10 for water use efficiency. The foreground selection has been carried out in two generations i.e., BC1F1 and BC2F1. Also, Background selection has been done in BC1F1 to check the background recovery of recurrent parent. The plants carrying the QTL with highest recurrent parent background recovery were selected and again backcrossed to respective parent for generation of BC3F1 population. The BC3F1 plants have been raised during Kharif 2019. The development of drought tolerant PMH10 hybrid will lead to overcome frequent irrigations during spring season and helps to conserve ground water depletion.
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