Development Of Rice Breeding Lines Resistance Against Brown Planthopper By Molecular Marker-assisted Selection

Rice is one of staple grain crops in the world,rice production is crucially important to global food security.Brown planthopper?BPH,Nilaparvata lugens St?l?is a devastating insect pest for rice production,which can causes yield loss and quality deterioration.Moreover,the excessive insecticide application seriously break the balance of ecosystems.Host-plant resistance is one of the most cost-effective approach for BPH controling.‘Huanghuazhan?HHZ?'and‘Wushansimiao?WSSM?'are high-quality and high-yield inbred rice varieties developed by Rice Research Institute,Guangdong Academy of Agricultural Sciences,and are widely cultivated in Hubei province at present,but susceptible to BPH.In this study,we intend to introgress the BPH resistance genes,Bph14 and Bph15,into the genetic background of‘Huanghuazhan'and‘Wushansimiao'by backcrossing and molecular marker-assisted selection?MAS?,and selecting new breeding lines through identification of BPH resistance,yield testing and grain quality analysis.The aim is to develop BPH-resistant improved lines,which maintain the same growth duration,yield,and quality as the recipient.Hence,it supplies with breeding materials for developing BPH-resistant inbred varieties.All of the scientific research work before BC₃F₂ was completed by Wang Hongbo.I taked over the work in BC₃F₂.The major results of the study are as follows:1.Eight breeding lines carrying homozygous Bph14 and Bph15 genes were selected from the progenies of‘HHZ⁴/HB13001-14-5'by the detection of target genes,yield test,invsgating the major agronomic traits and rice quality analysis,which were designated as HB16005-1-3-49,HB16005-1-3-60,HB16005-2-6-8,HB16005-5-1-43,HB16005-5-1-80,HB16005-5-7-9,HB16005-5-7-29 and HB16005-5-7-40,respectively.Seven breeding lines carrying homozygous Bph14 and Bph15 genes were selected from the progenies of‘WSSM⁴/HB13001-14-5',which were designated as HB16003-7-1-24,HB16003-7-1-44,HB16003-8-7-2,HB16003-8-7-14,HB16003-8-7-50,HB16003-25-8-26 and HB16003-25-8-48,respectively.2.BPH bioassays at the seedling stage showed that recipient parents HHZ and WSSM with no resistance genes are susceptible to BPH?resistance score is 7.0?and highly susceptible to BPH?resistance score is 8.3?,respectively,all of the 15 selected breeding lines were highly resistant or resistant to BPH?resistance scores were 1.0³.7?,implying the BPH resistance of selected lines had been significantly enhanced.3.The rice whole-genome SNP array RICE6K was used to assay the genetic background of selected lines,and the results demonstrated that the size of linked fragments adjacent the target gene on chromosomes 3 and 4 are 18.99 Mb²1.19 Mb in all improved lines.Some improved lines were also introduced different size of fragments from the donor parent on other chromosomes.The background recovery frequencies of8 improved lines of HHZ accounted for 88.23%⁹4.52%,and 6 improved lines of WSSM ranged from 92.69%⁹4.9%.4.According to the NY/T1433-2014 Technical Regulations of Rice Cultivars Identification for SSR Markers Method,48 pairs of SSR markers were used to analyze the differences between the selected lines and recipient parents.The results indicated that HB16005-1-3-60,HB16005-5-1-43 and HB16005-5-1-80 show no difference in 48 pairs of SSR markers compare with HHZ,HB16005-1-3-49 and HB16005-2-6-8 show one different marker from HHZ,while HB16005-5-7-9,HB16005-5-7-29 and HB16005-5-7-40 have 3 different markers.Among the improved lines of WSSM,there is no polymorphic marker between HB16003-8-7-50 and WSSM.But HB16003-7-1-24,HB16003-7-1-44,HB16003-8-7-2,HB16003-8-7-14,and HB16003-25-8-48 all have one difference in 48 SSRs,in addition,the result of HB16003-25-8-26 was not applicable owing to seeds contamination,the results of DNA fingerprint revealed the genetic differences between improved lines and the recipient parents by 48 pair of SSR markers.5.The results of yield test and rice quality analysis at Hainan and Ezhou showed that several breeding lines from the offspring of HHZ⁴/HB13001-14-5 had an earlier growth duration by 2-3 days and shorter plant height about 2-6cm by compared with the recipient“HHZ”,and other agronomic traits of the breeding lines were as similar to HHZ.Two breeding lines,HB16005-2-6-8 and HB16005-5-7-40 were identified as to be promising.They could be used as substitute lines of HHZ as BPH-resistance varieties.The agronomic traits,yield and rice quality of most breeding lines from the offspring of WSSM⁴/HB13001-14-5 were as similar to that of recipient,WSSM,except for a little increasing of plant height and 1000-grain weight.HB18003-7-44 was considered as a promosing breeding line for replace of WSSM as a BPH-resistance isogenic line in farmer planting.6.According to the results of yield tests,the major agronomic traits and rice quality analysis,four hybrid combinations with short growth period,high yield and good quality were selected.These four promising combinations were Hua5325S/HB16005-2-6-8,Hua5325S/HB16003-7-1-44,Hua6421S/HB16005-2-6-8 and Hua6421S/HB16003-7-1-44.They will be planed to produce hybrid seeds in future breeding activities and arranged as multi-site adaptability test.