RELATIONSHIP AMONG WATER USE EFFICIENCY, CANOPY TEMPERATURE, CHLOROPHYLL CONTENT AND SPOT BLOTCH (COCHLIOBOLUS SATIVUS) RESISTANCE IN DIVERSE WHEAT (TRITICUM AESTIVUM L.) GERMPLASM

摘要

The food security vision for 2050 has front- lined wheat as the major conduit to feed the global populace estimated at9.2 billion. Pakistan ranks 6th in world population and among the top ten countries for wheat production, but annual yieldproductivity appears to be stagnated due to prevalence of various biotic and abiotic stresses. More recently the incidence of anew foliar wheat disease spot blotch (Cochliobolus sativus) in drought and heat stressed areas of Pakistan has necessitatedthat a new look on both water use efficiency and spot blotch resistance be taken. Hence this study has attempted to establisha relationship between these two stress influencing constraints. One hundred lines were assessed for intrinsic water useefficiency, canopy temperature, chlorophyll concentration index and spot blotch resistance. Rates of photosynthesis (A) andtranspiration (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 physiologicalchanges 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 concentrationindex and spot blotch resistance. Keeping three growth stages (GS: 63, GS: 69 and GS: 77) as a source of variation, dataanalyses have shown a significant difference amongst the studied attributes. Structural model equation revealed that about87.8% variability was explained by the studied attributes. Looking at significance of mean square values of % severity, 17wheat lines were found spot blotch resistant. These lines are valuable breeding stocks for wheat improvement for hotecological niches within Pakistan and globally where higher incidence of spot blotch prevails.