The wheat industry rejects grain with unacceptably high α-amylase enzyme levels due to the risk of poor endproduct quality. There are two main causes of elevated grain α-amylase: (1) preharvest sprouting in response to rain before harvest and (2) late maturity α-amylase (LMA) induction in response to a cool temperature shock during late grain development. LMA induction was detected in a panel of 24 Northwestern US spring wheat lines. Thus, this problem previously described in Australian and U.K. varieties also exists in U.S. varieties. Because LMA induction results were highly variable using published methods, a characterization of LMA-inducing conditions was conducted in an LMA-susceptible soft white spring wheat line, WA8124. Problems with elevated α-amylase in untreated controls were reduced by raising the temperature, 25°C day/18°C night versus 20°C day/10°C night. LMA induction was not improved by colder temperatures (15°C day/4°C night) versus moderately cold temperatures (18°C day/7.5°C night or 10°C day/10°C night). While previous studies observed LMA induction by heat stress, it failed to induce LMA in WA8124. Thus, not all LMA-susceptible cultivars respond to heat. The timing of LMA susceptibility varied between two cultivars and within a single cultivar grown at slightly different temperatures. Thus, variability in LMA induction likely results from variability in the timing of the grain developmental stage during which cold shock induces LMA. Thus, it was concluded that the visual inspection of grain is needed to correctly identify LMA-sensitive spikes at the soft dough stage of grain development (Zadok's stage 85).

中文翻译：

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使用美国西北部春小麦 (Triticum aestivum L.) 研究诱导晚熟 α-淀粉酶 (LMA) 的条件

由于最终产品质量差的风险，小麦行业拒绝接受具有不可接受的高α-淀粉酶水平的谷物。谷物α-淀粉酶升高的主要原因有两个：（1）收获前因雨水而发芽和（2）晚熟α-淀粉酶（LMA）诱导，以应对谷物发育后期的低温冲击。在一组 24 个美国西北部春小麦品系中检测到 LMA 诱导。因此，先前在澳大利亚和英国品种中描述的这个问题在美国品种中也存在。由于使用已发表的方法，LMA 诱导结果差异很大，因此在 LMA 易感软白春小麦系 WA8124 中进行了 LMA 诱导条件的表征。通过提高温度（白天 25°C/夜间 18°C）减少了未经处理的对照组中 α-淀粉酶升高的问题相对20°C 白天/10°C 夜晚。较冷的温度（白天 15°C/晚上 4°C）并未改善 LMA 诱导相对温度适中（白天 18°C/晚上 7.5°C 或白天 10°C/晚上 10°C）。虽然先前的研究观察到热应激引起的 LMA 诱导，但它未能在 WA8124 中诱导 LMA。因此，并非所有对 LMA 敏感的品种都对热有反应。LMA 易感性的时间在两个品种之间以及在稍微不同温度下生长的单一品种内有所不同。因此，LMA 诱导的变异性可能是由冷冲击诱导 LMA 的谷物发育阶段时间的变异性引起的。因此，得出的结论是，在谷物发育的软面团阶段（Zadok 的第 85 阶段），需要对谷物进行目视检查以正确识别 LMA 敏感的尖峰。