机插密度和穗肥减量对优质食味水稻品种籽粒淀粉合成的影响

Effects of machine transplanting density and panicle nitrogen fertilizer reduction on grains starch synthesis in good taste rice cultivars

机插密度对优质食味水稻品种籽粒淀粉合成的影响尚不明确。试验以3个江苏省代表性优质食味水稻品种南粳9108、南粳5055和南粳46为材料,行距固定为30 cm,通过设置10、12、14、16和18 cm株距,形成33.3×10^(4)、27.8×10^(4)、23.8×10^(4)、20.8×10^(4)和18.5×10^(4)穴hm^(-2)5种机插密度,研究了机插密度对上述优质食味水稻品种产量和籽粒淀粉合成的影响,并观察了穗肥施氮量减半施用对优质食味水稻籽粒淀粉合成的调控效应。结果表明:(1)3个优质食味水稻品种产量均在密度为27.8×10^(4)穴hm^(–2)时最高。成熟期稻米直链淀粉含量随机插密度增加呈先下降后上升的趋势,支链淀粉含量则不断下降。机插密度控制在27.5×10^(4)~29.9×10^(4)穴hm^(–2)时,有利于提高上述优质食味水稻品种的食味值。(2)随机插密度增加,颗粒结合态淀粉合成酶(granule-bound starch synthase,GBSS)和ADP-葡萄糖焦磷酸化酶(ADP-glucose pyrophosphorylase,AGP)在籽粒灌浆前中期(抽穗后8~20 d)的活性有所上升,但在灌浆后期迅速下降,而机插密度对淀粉分支酶(starch branching enzyme,SBE)活性无明显影响。其中,抽穗后12~16 d籽粒中GBSS和AGP活性与直链淀粉和总淀粉含量呈显著或极显著正相关。(3)与正常穗肥相比,穗肥减半处理能显著降低优质食味水稻品种灌浆前中期籽粒中GBSS和AGP活性,降低稻米直链淀粉含量,提升优质食味稻米的食味值。上述结果表明,机插密度可通过调控灌浆前中期籽粒中淀粉合成关键酶(GBSS和AGP)活性,调控直链淀粉含量进而影响稻米食味值。合理的机插密度和穗肥施用量有助于进一步改善优质食味稻米的食味品质。

The effect of machine transplanting density on grain starch synthesis in good taste rice cultivars(GTRC)is still unclear.In the experiment,three representative GTRC of Nanjing 9108,Nanjing 5055,and Nanjing 46 in Jiangsu province were used as materials.Five machine transplanting densities of 33.3×10^(4),27.8×10^(4),23.8×10^(4),20.8×10^(4),and 18.5×10^(4) hills hm^(–2) were formed with the row spacing at 30 cm and the plant spacing of 10,12,14,16,and 18 cm,respectively.The effects of machine transplanting density on yield and grain starch synthesis in above three rice cultivars were studied,and the regulation mechanism of halving normal nitrogen(N)rate of panicle nitrogen fertilizer on the starch synthesis was also observed.The results were as follows:(1)The grain yield of the three GTRC were highest at the transplanting density of 27.8×10^(4) hills hm^(–2).The amylose content at mature stage of the three GTRC decreased first and then increased with the increase in machine transplanting density,while the amylopectin content continued to decrease.When the machine transplanting density was controlled at 27.5×10^(4)^(–2)9.9×10^(4) hills hm^(–2),it was beneficial to improve the taste value of the above-mentioned GTRC.(2)With the increase in machine transplanting density,the activities of granule-bound starch synthase(GBSS)and ADP-glucose pyrophosphorylase(AGP)were increased in the early and middle stages of grain filling(8^(–2)0 days after heading),and were decreased rapidly at later grain filling stage.Machine transplanting density had no significant effect on starch branching enzyme(SBE)activity.Among them,the activities of GBSS and AGP in grains at 12–16 days after heading were significantly and positively correlated with the contents of amylose and total starch.(3)Compared with normal N rate of panicle nitrogen fertilizer,half normal N rate could significantly decrease the activities of GBSS and AGP in grains during the early and middle stages of grain filling,reduce the amylose content of rice,and further improve the taste value of GTRC.These results indicated that machine transplanting density could regulate the amylose content due to the activities variations of key enzymes involved in starch synthesis(GBSS and AGP)in the grains during the early and middle stages of grain filling,thus resulting in the difference of rice taste value.Reasonable machine transplanting density and panicle nitrogen fertilizer rate are helpful to further improve the eating quality of GTRC.