Fine Mapping Of A QTL For Strong Rice Culm And Analysis Of Its Candidate Gene

As the most important food crop in developing countries and also one of the most important staple foods in the world,rice has a pivotal position in global food security.Lodging is a main restriction factor in rice production for its extreme negative impact on rice yield and quality formation.Rice lodging can be affected by many factors,similarly,its lodging resistance is consist of multiple factors including plant height?physical characteristics and chemical components of culm?tiller angle?panicle type and so on.Culm diameter and wall thickness are the most important factors of culm physical characteristic and of great significance to rice lodging-resistance ability.In this study,we take Shuhui498?R498?and Yihui3551?R3551?for research objects,which have strong and slender culms respectively,to investigate the molecular mechanisim of R498's excellent lodging-resistance,and the main results are as following:1.It`s revealed that difference of culm diameter is the main reason that the mechanical strength of R498 is significant higher than that of R3551.2.By high density genetic linkage map through reduced-representation sequencing and fragment-overlap method,q PND1 was finally localized within 183kb on the short arm of Chromosome 1 and Os CKX2 was took as the candidate gene after analysis.3.The CDS and promoter of Os CKX2^R3551 were ransferred into R498,the PND of positive plants in T₁ generation decreased by 15.94%?18.13%and spikelet per panicle?SPP?dropped an average of 19.38%compared with R498.Meanwhile,we edited 2target sites on 1^st and 2^nd exon of Os CKX2 under the background of ZH11,a japonica rice variety,using Crispr/cas9 system.The PND of positive plants with different mutations increased by 12.34%?20.76%than CK,and SPP increased by an average of 21.21%.Breaking-resistance test and semi-thin section result showed that the breaking-resistanct strength of the 4^th internodes of positive lines increased by 42.71%?73.36%than ZH11,the number and area of macro-vascular bundles also increased.All those results indicated that Os CKX2 is a major gene for rice culm diameter and braking-resistance.4.We investigated the PND of pyramiding lines carrying different genotypes of Os CKX2 and SCM2,a major gene controlling rice culm diameter,in advanced BIL group constructed with R498 and Basmati.It turned out that the pyramiding of different genotypes of strong-culm genes showed an additive effect on panicle neck diameter.It indicates that pyramiding of different strong-culm genes maybe a feasible method for lodging-resistance improvement in rice.