RESPONSE OF SOME POTATO VARIETIES TO GROWTH AND PRODUCTION UNDER HIGH TEMPERATURE CONDITIONS: AN APPROACH TO IDENTIFY THE RESISTANT VARIETIES

Potato is a winter crop; the optimal temperature range is 20-25°C for haulm growth and 15–20 °C for tuberization. Recently climatic changes, provoked the importance of adaptability of varieties to high temperatures. For this reason, a study was conducted during 2018and2019 seasons at Vegetables Research Farm in Kaha, Qualiobia Governorate, totest the response of some potato varieties (Cara, Spunta, Barcelona and Valor) for cultivation during the summer months (first July, first August, first September and first October). Data were recorded to measure vegetative growth at 75 DAPS while yield parameters were recorded at harvesting time. Concerning differences between planting dates, the results showed that the planting in October gave the best results for vegetative growth and yield in all tested varieties, while September plantation came the second place. Planting during July and August caused dramatic effects on vegetative growth and yield. Furthermore, the cv. Cara gave higher significant growth measurements (stem length, weight of tubers plant, fresh and dry total weight, CGR and RGR). Also, Cara gave also the highest stem number, leaves number, tubers number and close to that obtained from cv. Valor in both seasons. Cara variety produced the highest tuber yield and its components followed by Barcelona, and then Valor and Spunta, in both seasons. Moreover, the interaction between the tested varieties and planting dates showed that the most tolerant cultivars during the high temperature months (July and August) was Cara in the first place, then Valor and Barcelona in the second rank, while Spunta cv. was the most sensitive cultivar. In general, it is recommended for early potato planting in summer months (July and August) under Egyptian conditions the choice of varieties which exhibit tolerance to stresses as Cara, Valor or Barcelona and avoid planting susceptible varieties as Spunta in these months.