Abstract
Plant physiological parameters such as membrane thermostability, canopy temperature depression, leaf chlorophyll content and yield related traits like no. of spikelets per spike, no. of grains per spike, 200-grain weight and grain yield of 18 wheat genotypes were carried out to assess for heat tolerance. Performances of all the genotypes were found to have significant differences for all the traits except canopy temperature depression. But, canopy temperature depression with some other traits like leaf chlorophyll content, no. of grains per spike, 200-grain weight and grain yield per plant demonstrated significant differences when it grown in heat stress condition. In general, genotypes with higher leaf chlorophyll content and enhanced membrane thermostability demonstrated higher 200-grain weight or grain yield. Besides, in spite of having heat tolerant traits, several genotypes performed poor due to their poor genotypic potential. The present investigation has successfully isolated several genotypes viz. H024, H023, H022 and H018 with desirable traits related to heat tolerance based on overall performance while grown under heat stress. These genotypes can be used as gene source for future breeding program to improve heat tolerance of the local wheat cultivars.
 J. Bangladesh Agril. Univ. 16(3): 457–463, December 2018
Highlights
Wheat (Triticum aestivum L.) is an important cereal crop, grown in wide range of environments in the world (FAO, 2013)
There are some physiological traits used as selection criteria for heat tolerance in wheat, and have strong correlation with grain yield under heat stress. viz. membrane thermostability (Sharma et al, 2016; Yildirim et al, 2009; Reynolds et al, 1994), canopy temperature depression (Bahar et al, 2008; Reynolds et al, 1994, 2001), chlorophyll content (Yildirim et al 2011), stomatal conductance (Reynolds et al 1994), grain number per spike, grains per spikelet and thousand grain weight and grain yield (Pimentel et al, 2015)
Analysis of variance (Table 1) showed that, for canopy temperature depression (CTD) there was no significant variation among the genotypes and genotype-treatment interaction does not have any effects on the genotypes
Summary
Wheat (Triticum aestivum L.) is an important cereal crop, grown in wide range of environments in the world (FAO, 2013). In Bangladesh, wheat plants received the sudden high temperature stress from the very beginning of March or just after end of winter season when plant reaches to grain filling stage. With every 1oC increase in temperature from 28oC during grain filling period results 3–4% yield reduction (Reynolds et al 1994, 1998; Wardlaw et al, 1989). Another important problem is getting short winter period due to late planting of wheat, which exposed wheat plants to heat stress and offers short grain filling period. The main objective of this study was to evaluate some exotic wheat genotypes to identify heat tolerant genotypes for using in future breeding program and to prepare a ranking table on the basis of physiological traits to identify the best genotype
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