Abstract:

Lodging is a bottleneck problem of restricting the high quality and high yield of rice （Oryza sativa L.） under the rice-crayfish coculture. To study the effect of exogenous melatonin spraying on the lodging characteristics of rice stems under rice-crayfish coculture， ‘Nanjing 5718’ was as the experimental material， and the experiment set two treatments： 200 μmol·L^-1 melatonin foliar-spraying ^{at the early stage of jointing （MT） and control treatment （CK）. The morphology index， culm mechanics index， culm chemical composition content， rice yield and the expression levels of key genes for lignin and cellulose biosynthesis under different treatments were determined. The results showed that the rice yield of MT treatment was 9 261 kg·hm-2， which had no significant difference with CK treatment， however， the spikelets per panicle of MT treatment significantly increased than that of CK， while the effective panicles and seed setting rate significantly decreased. Compared with CK treatment， the plant height， panicle length and gravity center height of MT treatment significantly decreased by 13.04%， 14.91% and 22.93%， respectively. The flexural resistance and breaking strength of the second internode significantly increased by 22.39% and 22.34%， and bending moment and lodging index significantly decreased by 20.61% and 35.03%. And the expression levels of key genes for lignin and cellulose biosynthesis including OsCoMT， OsCesA4， OsCesA7 and OsCesA9 genes were upregulated under MT treatment. Correlation analysis showed that the lodging index of MT treatment was extremely significantly positively correlated with plant height， panicle length， and length from breaking point to panicle top， and was significantly negatively correlated with flexural resistance， breaking strength， and bending stress. In conclusion， spraying melatonin could improve the lodging resistance of rice stem under the premise of stable rice production in the rice-crayfish coculture mode， which provided theoretical and practical guidance for the regulation of rice lodging resistance under the rice-crayfish coculture mode.}

Key words: melatonin, lodging resistance, yield formation, rice-crayfish coculture, plant growth regulator

摘要：

倒伏是限制稻虾共作模式水稻优质高产的瓶颈问题。为研究外源褪黑素喷施对该模式下水稻茎秆倒伏特性的影响，以‘南粳5718’为试验材料，在稻虾共作模式下于拔节初期叶面喷施200 μmol·L^-1褪黑素处理（MT），以未喷施为对照（CK），比较不同处理下水稻的形态学指标、茎秆力学指标、茎秆化学成分含量、水稻产量及木质素、纤维素生物合成关键基因的表达。结果表明，稻虾共作模式下，MT处理的水稻产量为9 261 kg·hm^-2，与CK差异不显著；但MT处理的穗粒数较CK显著增加，而有效穗数和结实率较CK显著降低。与CK处理相比，MT处理水稻的株高、穗颈节高度和重心高分别显著降低13.04%、14.91%和22.93%，而第2节间抗折力和折断弯矩显著增加22.39%和22.34%，弯曲力矩和倒伏指数显著降低20.61%和35.03%；木质素、纤维素生物合成关键基因OsCoMT、OsCesA4、OsCesA7和OsCesA9表达上调。相关性分析表明，MT处理下，倒伏指数与株高、穗颈高度和折断部位至穗顶距离呈极显著正相关，与抗折力、折断弯矩和弯曲应力呈显著负相关。综上所述，稻虾共作模式下喷施褪黑素可在水稻稳产的前提下提高水稻茎秆抗倒伏能力，为稻虾共作模式下水稻抗倒栽培调控提供理论和实践指导。

关键词: 褪黑素, 抗倒伏, 产量形成, 稻虾共作, 植物生长调节剂