Gas exchange characteristics, water use efficiency and osmotic adjustment in relation to heterosis in hot pepper (Capsicum annuum L.) under water stress

Two hybrids and parents (hyb MSH-11; IHR 3289 male, IHR3285femaleand hybECH-86; IHR2444 male, IHR AR 18 female parents) of hot pepper (Capsicum annuum L) were studied to examine the response of morphological attributes, net photosynthetic rate (P_N), stomatal conductance (g_s) and water use efficiency (WUE) under control (irrigated) and water stress conditions. Water stress was imposed at flowering stage under field condition by withholding the irrigation for a period of 35 days. Both the hybrids responded differentially to water stress. In general, the plant height, fruit numbers, fruit fresh weight and total dry matter (TDM) accumulation were higher in hybs than their respective parents in control as well as stress conditions. The fruit bearing and TDM accumulation were more in hyb MSH-11 compared to the hyb ECH-86. The hyb ECH-86 had the higher P_N compared to parents under control as well as stress conditions. However, in hyb MSH11, there was no definite patter in P_N under control but it was greater than parents under water stress. Though, in both the hybs P_N decreased substantially after 21 days of stress, the quantum of decrease was more in hyb ECH-86 than hyb MSH-11. Further MSH-11 had shown better osmotic adjustment (OA) than hyb ECH-86. The higher WUE of hyb MSH-11 than its parents under control and stress conditions shows the heterosis for WUE in this hybrid. WUEwashigher in hybMSH-11(2.5μmolCO₂/mol H₂O) as compared to hyb ECH-86 (2.0μ mol CO₂/mol H₂O) under stress which may be due to the higher P_N in this hybrid under stress. The heterosis for TDM, P_N and WUE in hyb MSH-11 under stress may be a contributing factor for better performance of this hyb under stress.