Water strategy improves the inflorescence primordia formation of 'Arra 15' grapevine in the Brazilian semiarid region.

Failure in irrigation management of grapevines grown in the Brazilian semiarid region can affect bud fertility. Adequate irrigation, considering both the development of bunches in the current cycle and the formation of fertile buds for subsequent cycles, can bring significant advances to viticulture. Therefore, the objective of this research was to investigate the effect of different irrigation levels during flowering on the formation of buds and potential bunches of 'Arra 15' grapevine and its relationship with metabolic processes. A field experiment was carried out in a commercial vineyard in Petrolina, Pernambuco, Brazil, during the 2021 and 2022 seasons. The experiment was designed in randomized blocks with four replications and five irrigation levels (70; 85; 100; 115 and 130% of crop evapotranspiration - ETc) during three production cycles. The variables fertile bud, vegetative bud, dead bud, potential fertility of the basal, median, and apical regions of the branches, number of potential bunches, reducing sugar, total soluble sugar, net photosynthesis, stomatal conductance, transpiration, and relative chlorophyll index were evaluated. The 115% ETc irrigation level improved the number of fertile buds and number of potential bunches. Irrigation level above 115% ETc increased gas exchange and relative chlorophyll index, while 70% ETc increased leaf sugar content. The most appropriate irrigation strategy is the application of 115% ETc during the flowering stage, for the increase of fertile buds and potential bunches of the next cycle, without influencing the vine metabolism. Total soluble sugars are a promising indicator of water deficit during flowering and as an indicator of vegetative bud formation for the next cycle.

Selection of cowpea cultivars for high temperature tolerance: physiological, biochemical and yield aspects.

High temperature stress can hinder the development of cowpea resulting in several damages including vegetative and reproductive phases of the crop. In this context, the objective of this study was to select cowpea cultivars tolerant to high temperature stress using various parameters related to physiological, biochemical, and yield aspects. For this, the cultivars Carijó, Itaim, Pujante, Rouxinol, and Tapahium were used, maintained in two temperature regimes: 20-26-33 °C and 24.8-30.8-37.8 °C. The experiment was carried out in growth chambers, in a 5 × 2 factorial arrangement (cultivars × temperature regimes). Responses differentiated among the cultivars Carijó, Itaim, Pujante, Rouxinol, and Tapahium with the increase of 4.8 °C in air temperature. The high temperature promoted a greater quantity of aborted flowers, leading to a reduction in the yield of the cultivars Carijó, Pujante, Rouxinol, and Tapahium. The photosynthesis, stomatal conductance, leaf transpiration and enzymatic activities were significantly influenced by high temperature. From the combination of the responses of biometric, physiological and productive variables, the cultivar Itaim can be considered as tolerant to an increase of 4.8 °C in air temperature.