Seventy-eight doubled haploid (DH) lines, derived from 21 elite and diverse winter × spring wheat F
1
hybrids, following the wheat × maize system, were screened along with the parental genotypes under
in vitro
and
in vivo
conditions for cold tolerance. Under
in vitro
conditions, the 2,3,5-triphenyl tetrazolium chloride (TTC) test was used to characterize the genotypes for cold tolerance. Based on the TTC test, only one doubled haploid, DH 69, was characterized as cold-tolerant, seven DH and five winter wheat parents were moderately tolerant, while the rest were susceptible. Analysis of variance under
in vivo
conditions also indicated the presence of sufficient genetic variability among the genotypes (DH lines + parents) for all the yield-contributing traits under study. The correlation and path analysis studies underlined the importance of indirect selection for tillers per plant, harvest index and grains per spike in order to improve grain yield. It was also concluded that selection should not be practised for grain weight per spike as it would adversely affect the grain yield per plant. When comparing the field performance of the genotypes with the
in vitro
screening parameters, it was concluded that in addition to the TTC test, comprising a single parameter, other physiological and biochemical
in vitro
parameters should be identified, which clearly distinguish between cold-tolerant and susceptible genotypes and also correlate well with their performance under field conditions.
Evaluation of heat stress tolerance in spring wheat (Triticum aestivum L.) genotypes using stress tolerance indices in western region of Nepal