Ácido salicílico atenua os efeitos da restrição hídrica em cultivares de feijão-caupi [Vigna unguiculata (L.) walp] em condições de campo

Abstract

Cowpea is a legume widely cultivated in the North and Northeast of Brazil, where it plays an important socioeconomic role. In these regions, the yield of this crop is strongly affected by the occurrence of water déficit during the cultivation period, which promotes a series of morphological and metabolic changes, restricting its production. To mitigate these effects, the use of resistance-inducing substances, such as salicylic acid, has been studied. Thus, the present study was carried out with the objective of evaluating salicylic acid as a water stress attenuator in cowpea cultivars, cultivated under irrigation depths in field conditions. The experiment was carried out in Lagoa Seca-PB, using a randomized block design where 4 cowpea cultivars (BRS Novaera, BRS Tapaihum, BRS Pujante and BRS Pajeú), 2 irrigation depths (W100 -) were studied. 100% of water replacement of the water evapotranspiration by the culture (ETc); and W50 - 50% of water replacement of ETc) and 3 concentrations of salicylic acid (Zero, 2mM and 4mM), in a 4x2x3 factorial scheme, with 3 replications. Evaluations of water status (leaf water potential and relative water content), electrolyte leakage, biochemical (free proline content, total soluble sugars, ascorbate peroxidase and catalase), photosynthesis and gas exchange, and production components were carried out in the phenological stages V7, R2 and R5. Data were subjected to analysis of variance (F test up to 5% probability), followed by Student's t-test (P ≤ 0.05) for irrigation depths, and Tukey's test (P ≤ 0.05) for AS cultivars and concentrations, using SISVAR 5.6 software. Water restriction reduced the water status, growth and photosynthetic processes of cowpea cultivars, however, under stress conditions, salicylic acid mitigated the effects of water restriction, which could be perceived by increases in growth, water status, photosynthesis and the content of osmoregulatory molecules and antioxidant enzymes. The yield of cultivars BRS Novaera, BRS Pujante and BRS Pajeú was significantly reduced by water limitation, however, in cultivar BRS Pujante this effect was circumvented by the application of salicylic acid. Cultivars BRS Novaera, BRS Tapaihum and BRS Pujante showed higher yields with the application of AS in blade W100. Among the cultivars studied, BRS Tapaihum was more tolerant to water restriction, while cultivar BRS Pujante was more responsive to SA application under stress conditions. Furthermore, the concentration of 2mM of AS proved to be more efficient in mitigating the effects of water déficit.