Abstract

Citrus, an important fruit crop in the Mediterranean region is significantly affected by climate change, which affects plant morphology and physiology. Grafting has improved the citrus industry. In this study, we studied the impact of water stress, 100%, 75%, and 50% substrate field capacity on seedlings of new hybrid citrus rootstocks. Growth rates, stomatal conductance, and fresh and dry weights were assessed, and proline, soluble sugar, and chlorophyll contents were estimated. Water stress affected all citrus rootstock seedlings. The growth parameters decreased with increasing stress levels. According to growth parameters, Poncirus trifoliata×Citrus Volkameriana seedlings were the least affected, followed by Poncirus Trifoliata×Citrus reshni Hort. ex Tan. (H1) seedlings, whereas those of Poncirus trifoliata×Citrus reshni Hort. ex Tan. (H2) were the most affected. Seedlings of Poncirus trifoliata×Citrus reshni Hort. ex Tan. (H5) accumulated less proline, whereas Poncirus Trifoliata×Citrus reshni Hort. ex Tan. (H3) had the highest content. The chlorophyll content and stomatal conductance decreased with increasing drought stress. Overall, the Poncirus trifoliata×Citrus volkameriana rootstock was more tolerant to drought stress, and the Poncirus trifoliata×Citrus reshni Hort. ex Tan. (H2) appeared to be sensitive. Future citrus breeding programs should prioritize the development of rootstocks that can tolerate dry conditions.

Key words: citrus, drought, hybrid, rootstock, water stress, growth