Characterization of a Nagina22 rice mutant for heat tolerance and mapping of yield traits

Heat is one of the major factors that considerably limit rice production. Nagina 22 (N22) is a deep-rooted, drought and heat tolerant aus rice cultivar. This study reports the characterization of a previously isolated dark green leaf mutant N22-H-dgl219 (NH219) which showed reduced accumulation of reactive oxygen species in leaf under 40A degrees C heat conditions. The mutant was characterized for several traits in field under ambient (38A degrees C) and heat stress (44A degrees C) conditions by raising temperature artificially from flowering stage till maturity by covering plants with polythene sheets during dry season 2011. Yield traits were mapped in 70 F-2 segregants of IR64 x NH219 and 36 F-2 segregants of its reciprocal cross. Leaf proteome analysis using two-dimensional gel electrophoresis from N22 and NH219 showed distinct constitutive expression of ribulose bisphosphate carboxylase large chain precursor (EC 4.1.1.39) in NH219 under ambient growth condition. Heat stress resulted in reduction of all 11 traits except plant height in both N22 and NH219. The extent of reduction was more in N22 than in NH219. Both pollen viability and spikelet fertility were not reduced significantly in N22 and NH219 but reduced by 20% in IR64. NH219 is more tolerant to heat stress than wild type N22 as its percent yield reduction is lesser than N22. Single marker analysis showed significant association of RM1089 with number of tillers and yield per plant, RM423 with leaf senescence, RM584 with leaf width and RM229 with yield per plant.