关键词: ABA, 小麦, 穗发芽, 籽粒品质

Abstract:

【Objective】Pre-harvest sprouting (PHS) resulted from higher rainfall during the harvest period is one of the crucial reasons degrade food uses quality of wheat flour in Southwest wheat production region of China. This study was carried out to investigate the inhibition effect of exogenous abscisic acid (ABA) to pre-harvest sprouting, and the changes in grain quality with respecting to PHS sensitivity was also measured. 【Method】Two cultivators with pre-harvest sprouting resistance (sensitive: white-seeded wheat Zhongkemai 138; insensitive: red-seeded wheat Mianmai 367) were used as experimental materials. The anti-photodegraded ABA (0, 50, and 100 mg·L ^-1) were sprayed at 15 (initial filling stage), 30 (late filling stage) and 35 days (physiological maturity stage) after anthesis (DAA) to investigate the changes in germination traits, α-amylase activity and grain quality. 【Result】 (1) The application of 50-100 mg·L ^-1 ABA at 30 DAA could inhibit PHS, with the optimum spraying time achieved at 30 DAA. In normal years (2018), the wheat spraying with 50 mg·L ^-1ABA was better than other treatments as compared to the control, the germination rate of Zhongkemai 138 was reduced by 13.8 and 3.8 percentage points at physiological maturity and dough stage, respectively, and the PHS sensitivity cultivator (Mianmai 367)was decreased by 23.5 and 9.7 percentage points, respectively, as compared with control. In 2019 (rainy season), spraying with 100 mg·L ^-1 ABA performed better than other treatments with the germination rate of Zhongkemai 138 was reduced by 22.5 and 19.6 percentage points during the physiological maturity and dough stage, respectively, as compared with control, and PHS sensitivity cultivator (Mianmai 367) was reduced by 10.0 and 12.0 percentage points than that of control, respectively. Meanwhile, the inhibitory effects of ABA were all released at 60 days after harvest, and did not affect subsequent seed germination. (2) Exogenous application of ABA could reduce α-amylase activity and inhibited α-amylase activity, which further delayed the hydrolysis of starch in 35-45 DAA. Compared with the control, the α-amylase activity and soluble sugar content were decreased by 30.1%, and 41.9%, respectively, and the starch content was 10.2 percentage points higher when the 100 mg·L ^-1 ABA was spraying at 30 DAA. (3) The application of 100 mg·L ^-1 ABA improved the precipitation value by 4.3%-8.8%, and exogenous application of ABA showed a greater impact on the starch content with the amylopectin content and total starch content increased by 8.1 and 7.6 percentage points, and the amylose/amylopectin ratio decreased by 18.2%. Further, the pasting properties of flour were also improved with the falling value, peak viscosity and disintegration value was 20.9%-24.2%, 26.5%-51.4% and 12.4%-43.4% higher than that of CK, respectively. 【Conclusion】The application of 50-100 mg·L ^-1 ABA at 30 DAA could effectively reduce pre-harvest sprouting by inhibiting α-amylase induced starch hydrolysis without decline the protein quality, and thereby improved the pasting properties of wheat flour by enhancing amylopectin and total starch contents, reducing the ratio of amylase and amylopectin. Therefore, the application of 50-100mg·L ^-1 ABA at 30 DAA was highly recommended for farmers to enhance the pre-harvest sprouting resistance and reducing the losses in food uses quality in Southwest wheat production region of China.

Key words: abscisic acid, wheat, pre-harvest sprouting, grain quality