Spot blotch and terminal heat stress tolerance in south Asian spring wheat genotypes

Abstract

Terminal heat stress and spot blotch disease (caused by Cochliobolus sativus) are the most important stresses responsible for significant yield losses every year in warm South Asian plains. Both of these stresses are very severe in late planted wheat, which is common in rice-wheat and rice-rice-wheat cropping systems. The development of genotypes tolerant to both stresses might be very useful for increasing yield and reducing yield losses. Information is limited on how different genotypes respond to both stresses (individually and combined) and on the degree of tolerance present in South Asian wheat genotypes. The study was done to evaluate the tolerance of South Asian wheat genotypes to both stresses by comparing the stress factor susceptibility index (SFSI). Eleven diverse South Asian genotypes were evaluated under spot blotch stress (non-fungicide protected plots), heat stress (late planted and fungicide protected), both stresses (non-fungicide protected and late planted) and normal planting situations (fungicide protected and normal season planted) at Rampur, Chitwan, Nepal. Both stresses reduced the grain yield and thousand-kernel weight (TKW), but not other yield components, including grains/spike and spikelets/spike. Genotypes BL 1473, Gautam and NL971 were moderately to highly tolerant to both types of stress. Generally genotypes that are tolerant or resistant to spot blotch also showed tolerance to heat stress, suggesting a common physiological mechanism to combat both stresses in tolerant genotypes.

The effect of spot blotch and heat stress on variation of canopy temperature depression, chlorophyll fluorescence and chlorophyll content of hexaploid wheat genotypes

“…On the other hand, BL1473, a highly susceptible genotype, showed tolerance to both spot blotch and heat stress (Table 3). The result is consistent with previous reports (Rosyara et al 2005(Rosyara et al , 2007(Rosyara et al , 2009b. BL1473 also showed higher compensation to removal of the flag and penultimate leaves (Rosyara et al 2005) indicating some type of compensation mechanism.…”

Combined effect of the drought duration and elevated atmospheric CO2 level on physiological and yield parameters of winter wheat

“…In the present work, water withholding at first node appearance resulted in higher grain mass per plant, but there was a decline in the thousand-kernel mass. In response to abiotic and biotic stress, Rosyara et al (2009) reported reductions in both the yield and the thousand-kernel mass, but observed no changes in other yield parameters. By contrast, in the present work water withholding in the early stage of development resulted in a decrease in the grain number.…”

Crosses with spelt improve tolerance of South Asian spring wheat to spot blotch, terminal heat stress, and their combination

“…Attributing to the fact that south Asian wheat growing season is characterised by high humidity and high temperature, it is favourable for spot blotch particularly during flowering and grain filling stage 2 , 18 . Heat stress and spot blotch have been found to be positively associated 19 . Moderate to warm temperature range (18 to 32 °C) generally favours the growth of spot blotch pathogen Bipolaris sorokiniana .…”

“…Most of earlier studies have focused on separate investigations of spot blotch or terminal heat stress in wheat, often in T. aestivum × T. aestivum crosses. Although a few studies have attempted to investigate the effects of the simultaneous stresses 11 , 19 , they do not provide comprehensive insights under controlled individual and combined stress conditions.…”