Phenotypic and physiological evaluation of drought resistance in seedling populations of Xinjiang native peach germplasm

【Objective】The Xinjiang native peach, referred to as Tutao, serves as the primary rootstock for seedling breeding in China. Evaluating the drought tolerance of these native varieties is crucial for understanding their resistance mechanisms and physiological traits, which can aid in enhancing selection of drought-resistant germplasm and rootstock varieties.【Methods】In this study, 21 germplasm accessions were subjected to simulated drought stress using varying concentrations of polyethylene glycol 6000 (PEG-6000) at 0%, 15%, and 25%, with 14 of these being Tutao. The seven potted wild and related germplasm seedlings with drought-resistant phenotypes including Baigen Gansutao No. 1, Honggen Gansutao No. 1 (Prunus kansuensis), Shantao 3-12 (P. davidiana), Xikang Biantao No. 3 (P. dulcis), Xi-kang Biantao No. 4 (P. dulcis), Sidaoling wild plum (P. salicina), and Yuyemei No. 1 (P. triloba), were used as controls. In the study, the effects of PEG-6000 were analyzed on malondialdehyde (MDA) and proline (PRO) levels, as well as peroxidase (POD) activity in the leaves of both peach and control groups.【Results】Results indicated that the Tutao group demonstrated a 50.10% higher germination rate, a 8.39% higher survival rate, and a 18.61% shorter germ length compared to the control group. Different seed sources would affect various germination indexes of seeds, which were closely related to drought resistance. The germination rate of Tutao was higher than that of other mainland varieties, indicating better seed fullness. The variation of drought stress damage index of different germplasm accessions ranged from 0 to 98.75%. The drought resistance of Tutao and control germplasm could be divided into three grades: Weak (＞80), Moderate (16-80), Strong (≤16). The results showed that there were 4 weak- drought- resistant germplasm accessions, 12 medium drought- resistant germplasm accessions and 5 strong-drought- resistant germplasm accessions. The five accessions with strong resistance were Shandao 3-12, Kunyu Youtao No. 1, Shache Bai Youtao No. 1, Shache Nuroutao No. 5, and Ruoqiang Nuroutao No. 1. The drought resistance levels among different quality types were as follows: Shandao demonstrated the highest drought resistance, Tutao had strong drought resistance, which also showed strong resistance. However, there was no significant difference in drought resistance between common peach and nectarine. In contrast, Gansutao exhibited medium resistance, while Xikang Biantao, Sidaolin wild plum, and Yuyemei showed low resistance. Based on the correlation analysis between drought resistance and the physiological indexes of MDA, PRO, and POD, it was determined that the drought resistance was positively correlated with MDA and PRO, while it had a negative correlation with POD. Therefore, germplasm accessions corresponding to its trend were selected for physiological index analysis. It was found that the contents of malondialdehyde (MDA) and free proline (PRO), and the activity of peroxidase (POD) in leaves of all varieties had significant differences with the increase of PEG- 6000 concentration, and the contents of malondialdehyde (MDA) and free proline (PRO) showed an overall upward trend. The peroxidase (POD) activity increased firstly and then decreased, and the physiological changes of Tutao were basically consistent with its drought resistance phenotype. The leaf drought damage of Xinjiang Tutao peach and control varieties was positively correlated with MDA and PRO contents, and negatively correlated with POD activity. MDA and PRO contents were positively correlated with each other (p＜0.05), and PRO content and POD activity were significantly and positively correlated with each other (p＜0.01). Progressive drought stress triggered significant accumulation of leaf proline to reduce the effect of drought stress. When the drought stress was mild, the activity of peroxidase in leaves increased to reduce the oxidative damage. However, the activity of oxidase decreased significantly when the drought stress intensified. The more drought- resistant varieties showed better physiological response, excellent ability to adapt to drought conditions, and to enhance the drought resistance of plants. The higher the antioxidant capacity of varieties, the stronger the drought resistance.【Conclusion】The results showed that: Firstly, the germination rate of the native peach germplasm was 50.11% higher than that of the control variety, which could be used as a highquality material for rootstocks; Secondly, the drought resistance of Tutao was stronger, and the tolerance to drought stress was higher; Finally, the selection of 4 excellent drought tolerance germplasm accessions provided a theoretical basis for further exploration of drought tolerance genes and breeding of drought-resistant varieties in Xinjiang native peaches.