Assessment of drought tolerance in some peach cultivars by chlorophyll fluorescence induction method

Water deficit stress has a significant effect on the growth and yield of peach plants. The aim of the study: to assess the effect of leaf tissue dehydration on the changes in chlorophyll fluorescence parameters and to identify cultivars highly tolerant to drought. The photosynthetic activity of the leaves was studied under native conditions, as well as after artificial dehydration. The studies of chlorophyll fluorescence were carried out on a MINI-PAM II portable pulsed fluorimeter (Heinz Walz, Germany, 2017). The investigations were made on leaves of four peach cultivars: ‘Asmik’ (Armenia), ‘Zempush’ (Azerbaijan), ‘Naryadny Nikitsky’ (Russia), and ‘San Lorenzo’ (Italy). The weight method was used to determine water content, water holding capacity and fluorescence indexes were calculated. The loss of water by the leaves per day was 34.5% in ‘San Lorenzo’, 35.4% in ‘Zempush’, 35.8% in ‘Asmik’ and 40.5% in ‘Naryadny Nikitsky’ from the initial weight of the samples. Despite the greatest water loss, ‘Naryadny Nikitsky’ demonstrated better activity of the photosynthetic apparatus under stress, compared to the other studied cultivars, and maintained high production processes. After 24 h of ‘Naryadny Nikitsky’ leaf dehydration, index F_v decreased by 23%, Y(II) – by 31%, and Y(NPQ) increased by 23%. Indexes PA, F_v/F_m, Rfd and Y(NO) did not change. According to the results of the experiments, ‘Naryadny Nikitsky’ was characterized by high adaptability of the photosynthetic apparatus to water stress. In addition, ‘Naryadny Nikitsky’ was characterized by the highest levels of chlorophyll a+b (5.06 mg g^‑1 dry matter).