Response And Sensitivity Difference Of Floret Opening Time In Diverse Ecological Types Of Japonica Rice Under MeJA Regulation

The Asian cultivated rice consists of two subspecies: Indica rice and Japonica rice.Hybridization between two subspecies above can create huge heterosis.Thus,direct utilization of heterosis from hybridization between indica rice and japonica rice is regarded as one of the most important methods of increasing rice yield significantly by most of the breeding researchers.However,floret opening time is early in Indica rice but late in Japonica rice.Meeting failure of floret opening time between two supspecies causes serious influence on outcrossing.Previous studies have shown that methyl jasmonate(MeJA)has a significant promoting effect on the flowering of indica rice,which can make the flowering time advance.MeJA can only be sprayed to the japonica-type parent in order to make floret opening time of parents meet.There are many kinds of japonica rice,is there any response and sensitivity difference among japonica rice cultivars in different ecological area with MeJA regulation? Very few research is reported in this area.In this study,we used 35 japonica rice cultivars from different ecological area to find out influence on floret opening time trait and agronomic traits with different concentrations of MeJA regulation.Scientific basis for improving seed production of hybrid rice between subspecies is provided.The research results are as follows:1.MeJA has a significant promoting effect on the flower traits of japonica rice in different ecological area.Compared with the control,the floret opening time of japonica rice under different concentrations of MeJA was significantly advanced on the first day after treatment,with the increase of MeJA concentration,the flowering-beginning-time,vigorous-flowering-time,flowering-ending-time of japonica rice were significantly advanced.The duration from flowering beginning to vigorous flowering,duration from flowering beginning to flowering ending were significantly shortened,duration from vigorous flowering to flowering ending was significantly extended.The influence extent was proportional to the concentration.2.Japonica rice cultivars from different ecological area have different sensitivity to MeJA regulation.The floret opening time traits of japonica rice cultivars are the most sensitive in Liaoning rice region and the least sensitive in the third accumulated temperature zone of Heilongjiang province to the regulation of MeJA.This may be related to the early hybridization of japonica rice breeding in Liaoning rice area.Breeding cultivars contain more indica ingredients.The third accumulated temperate zone of Heilongjiang Province is located in the cold zone,and more japonica ingredients are involved which is beneficial to improve cold resistance.3.Spraying MeJA has a significant effect on the plant type traits of japonica rice in different ecological area.Plant height and panicle curvature were decreased with the increase of MeJA concentration,and the concentration treatments were significantly lower than the control.The length of the flag leaf and the length of the second leaf increased with the increase of MeJA concentration.4.Spraying MeJA can significantly reduce the yield of japonica rice.And the greater the concentration is,the more obviously the degree of reduction causes.MeJA had no significant effect on the number of effective panicles and grains per panicle in yield structure,but had significant effects on seed setting rate and 1000-grain weight.In particular,the seed setting rate of primary branch and secondary branch were significantly decreased with the increase of MeJA concentration.It can be inferred that after spraying MeJA,the significant decrease in seed setting rate and 1000-grain weight is the main reason for the decline in yield of japonica rice.5.Spraying MeJA can significantly reduce the quality of japonica rice.Compared with the control,milled rice rate and head milled rice rate were decreased significantly under different concentrations of MeJA,and the greater the concentration is,the more obviously the degree of reduction causes.Spraying MeJA did not reach a significant level of chalkiness degree and chalky rice rate.The protein content of japonica rice was increased with the increase of MeJA spraying concentration,and the amylose content and taste score were decreased with the increase of MeJA concentration.6.We should hold a principle of “sterile indica restorer japonica” for application of hybrid rice breeding between indica and japonica subspecies.In this way we can utilize MeJA on restorer japonica rice which only provides pollen,and the adverse influence on yield and grain quality of sterile line of indica hybrids can be reduced;Under the premise of ensuring the encounter of flowering time,the MeJA concentration should be reduced as much as possible so as to save costs,reducing the loss of yield and rice quality of hybrid parents.