The Effects of Irrigation Methods on Proline- and Osmotic Stress-Related Genes of Grape (Vitis vinifera L.cv. Moldova) in Arid Regions

【Objective】 Metabolic activities and the genes coding them are modulated by soil water, and the aim of this paper is to study how a new irrigation technology - microfiber capillary core infiltration irrigation (MII) -affects soil water content, leaf water potential, expression of proline- and osmotic stress-related genes of grape in comparison with conventional irrigation methods. 【Method】 We used the Moldovan variety (Vitis vinifera L. cv. Moldova) as the model plant and conducted the experiment from May to September in 2019 in Yuquanying Farm at the eastern foot of Helan Mountain in Ningxia province. We compared three irrigation methods: conventional ditch irrigation (CK1), drip irrigation (D), and the new microfiber capillary core infiltration irrigation by burying the fibers at the depth of 10 cm; the irrigation amount in all of them was the same. To study the efficacy of MII in saving water, we also laid the capillary fibers over the soil surface and compared three irrigation accounts: the amount used in conventional irrigation (CK2), and reducing it by 2/3 (W1) and 1/3 (W2) respectively. In each treatment, we measured soil water content, leaf water potential, proline content of the fruits, and relative expression of P5CS genes. 【Result】 All treatments resulted in water stress though the degree of the stress varied. The water stress in CK1 was most severe persisting in 73% of the growing season, followed by C and D with the crop in the former and the latter suffering from water stress in 67% and 40% of its growth season respectively. The effects of the irrigation method on fruit yield, water use efficiency and irrigation water use efficiency were ranked in the order of C > D > CK1, and in the middle and later growth stage, the soil water content in C and D was higher than that in CK1. For MII, we did not find difference in water stress between the three irrigation amounts at significant level. The leaf water potential in CK1 was less than that in D, meaning that CK1 was more likely to have given rise to water stress, while its proline content was greater than that in D. For all data we measured, the leaf water potential was least in CK1 and largest in D, with that in C in between. Under different irrigation amounts in MII, the leaf water potential was ranked in the order of W2 <W1 <CK2 for data measured from July 13 to August 22, where the proline content in W2 was 1.1 to 1.8 times that that in CK2, depending on the sampling time. The yield, water use efficiency and irrigation water use efficiency were ranked in the order of W1 >W2 >CK2. Coding proline synthesis, the content of P5CS gene reflects the water stress and their relative expression in CK1 was significantly higher than those in D and C only from 4 to 28 August. Outside this window, there was no insignificant difference between them based on the data measured on July 25 and September 4. 【Conclusion】 Water use efficiency of D and MII was higher than that of CK1, indicating both microfiber infiltration irrigation and drip irrigations were water-saving. Among all treatments, the relative expression of P5CS gene was the highest in W1, indicating grapes in this treatment had been subjected to serious water stress despite achieving high yield and water use efficiency. Therefore, the superfine fiber infiltration is an improved irrigation method for grape production in arid regions as studied in this paper.