Effects of Different Spray Contents of KH2PO4 on Starch Synthesis and Expression of Genes Involved in Starch Biosynthesis in Rice
[Objective]The objective of this study was to determine how starch content is affected by KH2PO4.The study assessed starch content and genes involved in starch biosynthesis using different spray concentrations of KH2PO4 under the same cultivation conditions.[Method]Three rice cultivars with varying amylose content were used as experimental materials,employing a two-factor split-plot de-sign with four spray levels of KH2PO4.The study measured the expression levels of GBSSⅠ,BEⅠ,BEⅡb,SSⅡa,SSⅢa genes in the grains ten days after flowering.It also determined the total starch content,total protein content,and total lipid content in both polished and brown rice,as well as the amylose content and resistant starch content in polished rice.[Result]In the rice cultivar Hupo1,the amylose and resis-tant starch contents were significantly increased by spraying with KH2PO4,by 22.43%and 95.01%,re-spectively.However,in Hupo2 and Nuoyou1,the amylose content was significantly reduced by 6.75%and 64.24%,respectively.Conversely,spraying with KH2PO4 increased the resistant starch content of Hupo2 and Nuoyou1 by 55.63%and 43.07%,respectively.Expression analysis of key genes in the starch synthesis pathway revealed that the levels of GBSSⅠ,BEⅡb,BEⅠ,SSⅡa,and SSⅢa genes in the grains of the three tested rice varieties showed a trend of initial increase followed by a decrease.Spraying with KH2PO4 significantly increased the lipid content in both polished and brown rice of the three tested varieties,with increases of 72.64%,24.24%,and 4.71%in polished rice,and 25.88%,17.20%,and 7.81%in brown rice,respectively.In contrast,the total protein content in polished rice of Hupo1 and Hupo2 was significantly reduced by 19.71%and 22.15%,respectively.The total protein content of Nuoyou1 was affected differently compared to the other two varieties.In brown rice,the trend of protein content change in Hupo1 and Nuoyou1 was consistent with that in polished rice,while Hupo2 showed a different trend,with an increase in protein content of up to 30.30%.[Conclusion]KH2PO4 can increase the amylose and resistant starch content in specific rice cultivars,as well as the expression levels of key genes involved in the starch biosynthesis pathway,and increase the lipid content of both polished and brown rice,but reduce the protein content of polished rice.Based on the comparison of different spray concentrations,a 20 g/hm2 application of KH2PO4 contributed to the development of rice and ultimately improved its quality.
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