Water Relations, Gas Exchange, and Yield of Pepper Cultivars under Water Deficit Stress

Deficit irrigation has been used as an agricultural water management strategy to maximize water productivity in vegetable crops worldwide. Eight pepper (Capsicum spp.) cultivars in four distinctive groups differing in pungency levels (Serrano: Diablo and Alcon; Jalapeno: TAMU-JAL and TAMU-J222; Bell: 81447 and S1122; and Habanero: TMH and TAM-Orange) were evaluated under field conditions for their water relations, gas exchange (photosynthesis, intercellular CO₂, and stomatal conductance), and yield under water deficit.  The experiment was conducted in two sites, Uvalde in the Wintergarden region, and Amarillo in the Texas High Plains.  Pepper cultivars were grown at three irrigation levels (100%, 75%, and 50% of crop evapotranspiration (ET_c) requirement).  Peppers from the Habanero group had lower gas exchange rates, midday stem water potential, and yield than those in serrano, jalapeno and bell groups.  However, gas exchange and midday stem water potential within groups (jalapeno, bell and Habanero) were similar.  At both sites and across cultivars, the 50% ET_c treatment significantly reduced gas exchange rates, midday stem water potential and marketable yield.  The reduction of photosynthesis was mainly attributed to stomatal closure.  However, except for jalapenos at the Uvalde site, marketable yields within each group were similar at 100% and 75% ET_c treatments.  Therefore, deficit irrigation at 75% ET_c improved pepper water productivity in these water-limited regions of Texas.