| Ratooning rice has the advantages of labor-saving,time-saving,good rice quality,low production cost,and high economic benefit.In recent years,the combination of"mid-season rice+ratoon rice" is a new pattern of rice planting in south Henan Province.Even though there were many mid-season indica hybrid rice varieties,few of the varieties were suitable for ratoon rice cultivation.Furthermore,the classification of rice varieties with high yield,good rice quality,and strong ratooning ability are still unclear.There were few reports on the effects of alternate wetting and drying irrigation during the grain filling stage of the main crop rice on rice yields,ratooning rate,and rice quality of ratooning rice and their mechanisms.In this study,12 hybrid indica rice varieties,which were suitable for single-cropping rice,were used as materials.Under the conditions of field cultivation,the changes in their yields and rice quality were analyzed.In that case,rice varieties that were suitable for planting ratooning rice in south Henan Province were selected.Then,using the selected representative variety Liangyou 6326 as the material,three irrigation methods were set up during grain filling stage of the main crop rice,and their effects on grain yields,ratooning rate,and rice quality of ratooning rice were explored,which could provide theoretical and practical basis for the high-yield and high-quality cultivation of ratooning rice.The main results are as follows:1)According to the local grain yields of main crop rice and ratoon rice,the tested varieties were divided into four types:BH,with both high grain yields in main and ratoon season;HL,with high grain yield in the main season and low grain yield in ratoon season;LH,with low grain yield in the main season and high yield in ratoon season;BL,both low grain yields in main and ratoon seasons,the differences of rice quality were also analyzed.① The processing quality and appearance quality in ratoon season were significantly improved,however,the protein content in rice was decreased,and the tasting quality of rice was improved to different extents when compared with those in the main season;②Except for BL type(only one variety,Shenliangyou 11),the processing quality was better in the types of BH and HL,and HL had better appearance quality and cooking and tasting quality.There was no significant difference in protein content among the different yield types in the main season,while it was 10.7%higher and 1.75%lower in BH than those in HL and LH in ratoon season,respectively.③ The effect of daily average temperature after full heading on grain quality was far greater than the sunshine hours.The relatively low average daily temperature after full heading in ratoon season was the main reason for its better grain quality.Based on higher grain yield and better quality,Liangyou6326,Tianliangyou 616,Guangliangyou 476 and Fengliangyouxiang 1 were suitable varieties for ratoon cultivation in southern Henan Province.2)Compared with conventional irrigation(CI),alternate wetting and moderate soil drying irrigation(WMD)treatment increased the 1000-grain weight and seed setting rate of the main crop rice by 3.38%and 2.08%.Leaf photosynthetic rate,leaf Rubisco activity,leaf area index,root oxidation activity,zeatin+zeatin riboside(Z+ZR)content of stem,non-structural carbohydrate(NSC)content in stem and leaves,NSC content of stubble,regeneration rate,number of regenerated buds and effective panicle number in the ratoon season were all significantly improved,whereas the dry matter transfer rate,the decrease of NSC content in stem and leaves,and the contribution rate of NSC to grain were significantly reduced;alternate wetting and severe soil drying irrigation(WSD)exhibited the opposite effect.The results indicated that the WMD is beneficial to increase the photosynthetic capacity of the leaves in the main season,root activity,the NSC content of stubble,and the regeneration rate,thereby increasing the yield in ratoon season.3)Compared with CI,WMD treatment significantly improved the head milled rice rate,amylose content,protein content,and setback viscosity of the main crop rice,whereas the chalky grain rate,chalkiness,gel consistency,breakdown viscosity,and taste value were significantly reduced;WSD treatment slightly reduced the head milled rice rate and chalky grain rate of the main season rice,and slightly increased the protein content and breakdown viscosity.Whereas the chalkiness,gel consistency,and setback viscosity were significantly reduced,the amylose content and taste value were significantly increased.The rice quality of the ratoon season was better than that of the main season,but had no significant difference among the three irrigation treatments. |
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