Water Deficit Stress Modulates Nutrient Partitioning and Polygalacturonase Activity in Cape Gooseberry (Physalis peruviana L.) Fruits: Interactions with Calcium Supply

Global demand for cape gooseberry fruits has experienced significant growth in recent years. These fruits exhibit a physiological disorder known as cracking, caused by irregular water supply to the crop and calcium deficiencies. Therefore, the effects of different irrigation levels and calcium fertilization on fruit quality and on enzymes such as polygalacturonase, which is involved in cell wall degradation during ripening and stress responses. A completely randomized block design was used, with three blocks representing irrigation frequencies (4, 9, and 14 days) and twelve treatments arranged in a 4 × 3 factorial design. The first factor was the irrigation coefficient (0.7, 0.9, 1.1, and 1.3 of evaporation), and the second was calcium fertilization (0, 50, and 100 kg ha−1 of Ca2+ applied as calcium nitrate). Calcium fertilization did not affect the fruits’ calcium concentration [Ca2+]. Cape gooseberry plants fertilized with 50 and 100 kg ha−1 of calcium accumulated 57% and 107% more of this nutrient in the leaves compared to the control, while the calyx accumulated 72% more with calcium application. Irrigation coefficients of 1.1 and 1.3 of ETc reduced [Ca2+] in the leaves by 24% compared to irrigation coefficients of 0.7 and 0.9. [Ca2+] in the calyx decreased by 25% when the irrigation frequency was increased from 4 to 14 days. Numerically, the highest fruit concentrations of K+, Ca2+, and Mg2+ were observed under the combination of a 50 kg ha−1 calcium dose, a 0.9 irrigation coefficient, and a 9-day irrigation frequency. Polygalacturonase activity was significantly reduced by calcium fertilization, but irrigation treatments did not produce statistically significant effects.