Identification And Pyramiding Of QTL Related To Stigma Exsertion Rate Based On SSSL In Rice

Riceplays a key role in world food securiy, which is one of the world's four most important food crops and the staple of more than half of the global population.As is known to all, rice yield had been increased greatly by two quantum leaps, particularly thesecond leap. However, owing to low stigma exsertion rate of male sterilelines in rice,utilizationofheterosis and hybird production are limitedinricebreedingpractice. In order to solve these problems, here, we have identified and applicated QTL related to stigma exsertion rate based on 66 SSSLs in rice, which were contrusted from crossing between recipient, HJX74, and two donors, male sterility line(Oryza sativa L.) and Africa cultivated rice(Oryza glaberrima Steud.) respectively.The main results are as follows:1. For identifying QTL of stigma exsertion rate, we have detected a total number of 10 QTLs, distributing of chromosome 1, 2, 3, 5, 8, 11 and 12 respectively, 4 of which were derived from donor of male sterility line, 7 of which wereoriginated from donor of Africa cultivared rice.The QTL, mapped on chromsome 3, has been detected simultaneously under both donors which was treated as the same QTL in two kinds of materials. The substituedsegment average length of 10 QTLs was 15.12 c M, which we have detected for stigma exsertion rate, with thesubstitued segment length variation from 1.95 c M to 66.90 c M and the percentage of exserted stigma variation from 35.39% to 51.34%, with the addictive effect variation from 5.19% to 13.00% and thepercentageof additive effect variation from 21.53% to 52.29%. In this study, compared with previous studies, five( qpes-1a?qpes-2?qpes-3a?qpes-5and qpes-8a) of 10 QTLs about stigma exserton rate were reported and the same QTL likely.But the other five( qpes-1b?qpes-3b?qpes-8b?qpes-11 and qpes-12)QTLs identified here have not previously been detected.2. To study correlation between stigma exsertion rate and floral traits in rice, we havefound a significant positive correlation between the total length of stigma and style and stigma exsertion rate by utilizing SSSLs carrying QTL of stigma exsertion rate to explore correlation among varieties of floral traits, in the early and late seasons of 2015.The correlation coefficients are 0.37 and 0.67 respectively. Futhermore, the result by one-way analysis of variance hasshowed that there were a significant difference of total length of stigma and style and percentage of exserted stigmabetween selected SSSLs and HJX74. So, the total length of stigma and style was one of the main reasons which resulted in high percentage of exserted stigma. In the late season of 2015, because of interference of genetic backgroud and interaction of QTLs, we havefound no significant correlation betweent stigma exsertion rate and floral traits by utilizingpyramiding lines of QTL of percentage of exserted stigma to analyse correlation among floral traits.3.For analysing the pyramiding effects of QTLrelating tostigma exsertion rate in rice, we haveconcluded that the percentage of exserted stigmaof pyramiding lines including the QTL related to stigma exsertion rate fallen in between phenotypic values of the two SSSLswhich were constructed from donor of male sterility line. There were negativeand significant epistatic interactionamong QTLs with epistatic effectsvariation from-22.09% to-6.83% and with the contribution rates of epistatic effects variation from-51.51% to-23.98% and the difference betweenpracticle and theoretical additive effects variation from-11.01% to-2.65%. In the 2015 late season, we have concluded that the percentage of exserted stigma of pyramiding lines including the QTL related to stigma exsertion rate were higherthan phenotypic values of well SSSL parent which were constructed from donor of Africa cultivated rice.There were not only positive and no significant epistatic interaction but also accumulation effects among QTLs with epistatic effects variation from-0.22% to 4.33% and with the contribution rates of epistatic effects variation from-0.94% to 16.16%and the difference between practicle and theoretical additive effects variation from-0.11% to2.53%. HPS11/HPS14 with the best stigma exsertion rate( 64.57%) shows the stronger pyramiding effect. A35 should be regarded as the best choice to increase the percentage of exserted stigmaunder maintainer and selectedlines.Compared to their original parents,on the whole,excepted for grain length, other excellent traits of pyramiding lineskept at the maintenance level.In this paper, we have identified 10 QTLs of stigma exsertion rate and analysed correlation between stigma exsertion rate and floral traits and clarified the pyramiding effects and epistatic effects of QTL of percentage of exserted stigma.We believed that our resultscouldoffer a way to improve a part of stigma exsertion and could provide stonger theoretical andpractical foundationsfor increasing stigma exsertion rate through means of molecular breeding by designin rice.