RELATIONSHIP AMONG WATER USE EFFICIENCY CANOPY TEMPERATURE CHLOROPHYLL CONTENT AND SPOT BLOTCH COCHLIOBOLUS SATIVUS RESISTANCE IN DIVERSE WHEAT TRITICUM AESTIVUM L GERMPLASM
The food security vision for 2050 has frontlined wheat as the major conduit to feed the global populace estimated at 9.2 billion. Pakistan ranks 6 in world population and among the top ten countries for wheat production, but annual yield productivity appears to be stagnated due to prevalence of various biotic and abiotic stresses. More recently the incidence of a new foliar wheat disease spot blotch (Cochliobolus sativus) in drought and heat stressed areas of Pakistan has necessitated that a new look on both water use efficiency and spot blotch resistance be taken. Hence this study has attempted to establish a relationship between these two stress influencing constraints. One hundred lines were assessed for intrinsic water use efficiency, canopy temperature, chlorophyll concentration index and spot blotch resistance. Rates of photosynthesis (A) and transpiration (E) stomatal conductance (gs) and internal CO2 (Ci) were estimated using the Infrared Gas Analyzer (IRGA) Chlorophyll concentration index and canopy temperature were also measured to determine the extent of physiological changes under disease pressure. Spot blotch presence was estimated using the standard double digit disease scoring scale. Our results have revealed a direct relationship among water use efficiency, canopy temperature, chlorophyll concentration index and spot blotch resistance. Keeping three growth stages (GS: 63, GS: 69 and GS: 77) as a source of variation, data analyses have shown a significant difference amongst the studied attributes. Structural model equation revealed that about 87.8% variability was explained by the studied attributes. Looking at significance of mean square values of severity, 17 wheat lines were found spot blotch resistant. These lines are valuable breeding stocks for wheat improvement for hot ecological niches within Pakistan and globally where higher incidence of spot blotch prevails.