QlLs for response to low temperature stress during seedling growth in rice

Abstract

QTLs associated with growth of rice seedling under favourable and low temperature affected environments were mapped using a DH population derived from a cross between lowland indica variety, IR64 and upland japonica variety, Azucena. A dynamic approach to conventional mapping technique was employed in conjunction with a novel mapping technique termed as 'conditional mapping' using age-specific measures for seedling height, seedling weight and root depth. Among 15, 12 and 17 QTLs detected for seedling height, seedling weight and root depth, respectively, only 7, 6 and 2 QTLs for the respective traits were common to favourable temperature and low temperature affected environments indicating that, while a set of QTLs could hold the key to growth irrespective of growing environments, few QTLs with situation-specific expression might determine the differential response of the genotypes to environmental stress. The study also indicated that the difference in time of expression of some of the QTLs detected across growing environments might be additional feature of differential response of genotypes to varied growing environments. The conditional mapping technique allowed detection of 4 QTLs for seedling height and 6 QTLs each for seedling weight and root depth- which remained undetected by the conventional mapping technique indicating temporal pattern of gene expression and suggesting the importance of this technique in QTL analysis for developmental traits.