ASSESSMENT OF MORPHOLOGICAL AND PHYSIOLOGICAL RESPONSES OF PEACH ROOTSTOCKS UNDER DROUGHT AND ALUMINUM STRESS

The challenging constrain of peach production in highlands of northern Thailand is limited irrigation water and acidic soil. These problems could be alleviated by using a suitable rootstock. Field screening for drought and acidic soil tolerant rootstocks is time consuming and costly. Therefore, any parameter related to these traits detected in a greenhouse screening would be very useful as a selection index for a breeding program. In acidic soil, aluminum toxicity is one of the major confinements on plant growth. The aim of this study was to evaluate potential morphological (shoot fresh and dry weight, leaf size and leaf burn) and physiological (photosynthesis, chlorophyll a content, leaf conductance, leaf water potential and proline content) parameters related to drought and aluminum stress. A factorial experiment with two levels of the irrigation: 1) well watered (100% of evapotranspiration, ET) and 2) drought treatment (25-50% of ET), combined with three levels of aluminum: 1) no aluminum, 2) 50 mg kg-1 of aluminum and 3) 100 mg kg-1 of aluminum was done with four-week-old ‘Flordaguard’ rootstocks. The results showed that drought and aluminum stress caused leaf burn. Drought treatment significantly reduced shoot fresh weight (50%), shoot dry weight (35%), photosynthesis rate (80%), leaf conductance (90%) and leaf water potential (75%). Conversely, drought effect increased proline content by 10%. Aluminum stress caused linear decrease in shoot fresh weight and quadratic decrease in shoot dry weight and leaf size, but leaf burn was quadratic increased. For drought stress all parameters, except leaf size, leaf burn and chlorophyll content, were potentially selection index. Meanwhile, for aluminum stress, potential selection parameters were shoot fresh and dry weight, leaf size and leaf burn.