灌浆期高温对冬小麦籽粒氨基酸含量和组成的影响

Effects of high temperature during grain filling on the content and composition of amino acids in the grains of two winter wheat cultivars

以强筋小麦品种郑麦366和中筋小麦品种洛旱2号为材料,采用盆栽和人工气候室模拟的方法,研究了花后不同时段(灌浆前期即花后5 d,灌浆中期即花后15 d)和持续时间(处理2 d和4 d)的高温胁迫对籽粒氨基酸含量和积累量(以单粒中氨基酸含量表示)的影响。结果显示:(1)高温胁迫显著增加了小麦籽粒中必需氨基酸(EAA)、非必需氨基酸(NAA)和总氨基酸(TAA)含量,但降低了其积累量和EAA/TAA,2品种表现一致;(2)灌浆前期高温胁迫对2品种籽粒氨基酸含量的影响大于灌浆中期,而对氨基酸积累量的影响则相反;(3)高温持续时间对籽粒氨基酸含量的影响在2品种间存在差异,洛旱2号籽粒赖氨酸、EAA、NAA和TAA含量均随高温持续时间的延长显著增加,而郑麦366籽粒中上述指标仅在高温胁迫4 d下较对照增加显著;(4)从受高温胁迫的影响看,籽粒EAA/TAA对高温时段更敏感,而氨基酸含量表现为更易受高温持续时间的影响;(5)高温时段与持续时间的互作效应体现在:灌浆前期籽粒氨基酸积累量2品种均以高温胁迫4 d的影响最大,而灌浆中期则均以高温2 d的降幅最大。上述结果表明,小麦籽粒氨基酸及其组分对高温胁迫的响应不仅在品种间存在差异,且受高温时段和持续时间的影响。

High temperatures （HT） over 30℃ occur frequently during the wheat grain filling season in China, and have become an important limiting factor of wheat quality. To evaluate the impact of post-anthesis HT exposure on the amino acid content and composition of wheat grains, two winter wheat cultivars of different gluten strengths, Zhengmai366 （a high-gluten-strength cultivar） and Luohan2 （a medium-gluten-strength cultivar）, were investigated via a pot-culture experiment conducted at the experimental farm of Henan Agricultural University in Zhengzhou, China （113°35＇ E, 34°51＇ N）. The experiment was performed using a split-plot design with two developmental stages and two durations of HT treatment. The plants were exposed to HT （38℃） in a climate-controlled greenhouse from 11：00 to 16：00 at 5 days post-anthesis （DPA）, for 2 d and 4 d, and at 15 DPA for 2 d and 4 d. The control （CK） plants were treated at 28℃ in a different greenhouse. After the completion of treatment, the plants were returned to field conditions. The results were as follows：（1） post-anthesis HT significantly increased the lysine, essential amino acids （EAAs）, non-essential amino acids （NAAs）, and total amino acids （TAAs） content of the grains, whereas the EAA/TAA ratio and amino acid accumulation per kernel declined in both wheat cultivars. High temperatures had a stronger impact on the amino acid content of Luohan2 grains than on those of Zhengmai366. （2） The impact of HT on the amino acid content of grains was greater when HT was applied at an early stage of grain development （5 DPA） than when the treatment was applied at an intermediate stage of grain-filling （15 DPA）. However, with respect to the amino acid accumulation per kernel, the effect of HT exposure at the intermediate stage （15 DPA） was greater than when the treatment was applied at the early grain-filling stage （5 DPA）. （3） The amino acid content of the grains of the two wheat cultivars responded differently to different durations of HT treatment. The lysine, EAA, NAA, and TAA contents of the grains of Luohan2 significantly increased with prolonged exposure to HT. However, the lysine, EAA, NAA, and TAA contents of Zhengmai366 grains exhibited an initial decline after 2 d of HT, and then showed a significant increase after 4 d of HT. （4） The effects of the developmental stage and duration of HT exposure on the amino acid content of wheat grains differed between the two cultivars. The EAA/TAA ratio of both cultivars was strongly influenced by HT stage. With respect to amino acid content, Zhengmai366 exhibited greater sensitivity to HT duration, whereas Luohan2 exhibited a similar sensitivity to the different stages and durations of HT treatment. （5） Developmental stage and the duration of HT exposure interacted significantly to affect amino acid accumulation. During the early grain-filling stage （5 DPA）, 4 d of HT exposure resulted in the lowest amino acid accumulation per kernel, whereas 2 d of treatment at the mid-grain-filling stage （15 DPA） induced the lowest amino acid accumulation per kernel, in both cultivars. In conclusion, the influence of HT stress on the content and composition of amino acids in wheat grains during the early and mid-grain-filling stages depended not only on genotype, but also on the developmental stage at which the treatment was applied, and the duration of the exposure.