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Mapping of Flag Leaf Angle QTLs in Rice (Oryza Sativa L.)

Author: WangYingYing
Tutor: HongDeLin
School: Nanjing Agricultural College
Course: Crop Genetics and Breeding
Keywords: Rice Flag leaf angle Sensitivity to GA3 QTL mapping
CLC: S511
Type: Master's thesis
Year: 2009
Downloads: 66
Quote: 3
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Abstract

Hybrid rice seed production requires man-assisted pollination in order to enhance rate of outcrossing seed. In practice, the blade of flag leaf was cut by 1/2 to 1/3 to eliminate obstacle for outcrossing in CMS lines and restorer lines with small flag leaf angle. This procedure of leaf-cutting requires not only high-intensity laborious work, but also a higher level of operative technique in order to avoid cutting into young panicles being heading. In addition, wounds caused by leaf-cutting also had adverse effect on normal growth of rice plants. Identifiying favorable alleles of flag leaf angle is a foundation for improving the characters relating to outcrossing of male sterile lines through pyramiding merit alleles. Exogenous gibberellin (GA3) application has been a key technology in hybrid rice seed production. Improving flag leaf angle and sensitivity to GA3 of male sterile lines have important role in increasing yield and lowering cost of hybrid rice seed production. In this thesis, three studies have been conducted. Two studies have been conducted using a set of 98 backcross inbred lined (BILs), which derived from a backcross of Nipponbare(japonica) /Kasalath (indica)//Nipponbare by the sigle seed descent methods. First, we analyzed QTLs of flag leaf angle under 3 growing enviroments (E1 enviroment:Nanjing,2007; E2 enviroment:Nanjing,2008; E3 enviroment:Sihong,2008) and interactions betweem QTL and environments. Second, we studied sensitivity of flag leaf angle to exogenous GA3 and their QTLs dissection and their interaction with environments. The third study has been conducted using a set of 158 plants in BC1F1, which derived from a backcross ofⅡ-32B(indica)/A7444 (japonica)//Ⅱ-32B. SSR marker genotypes and phenotypes of flag leaf angle (FLA) were investigated in the 158 plants and their parents. SSR genetic linkage map of this cross was constructed. QTLs for flag leaf angle were detected. The results were as follows:1. For the BIL population which derived from a backcross of Nipponbare/Kasalath// Nipponbare, three QTLs for flag leaf angle were detected in 3 different growing environments, by using composite interval mapping method of Win QTL Cartographer 2.5 software, at 5% probability level of genome-wide type I error. The 3 QTLs located on chromosome 1,5 and 7. qFLA-7, located between C261 and C1057 on chromosome 7, was detected in E1 and E2 environments, explained 10.46% and 13.96% of phenotypic variance respectively. Positive alleles came from Kasalath. qFLA-1 was detected in E2 environments, which located between C970 and C161 on chromosome 1, explained 10.86 % of phenotypic variance. Positive alleles came from Kasalath. qFLA-5 was detected in E3 environments, which located between C466 and C246 on chromosome 5, explained 9.03% of phenotypic variance. Positive alleles came from Nipponbare.2. At the time of heading rate reaching 5%, exogenous GA3 and water (CK) were sprayed on every line of the BIL populations which drived from Nipponbare/Kasalath// Nipponbare respectively. Fifteen days after spraying, data of flag leaf angle were investigated. Results showed that flag leaf angle significantly increased in GA3 treatment than that in water control. But the increments for different lines were unequal. Using the same methods described above, three QTLs for responsive index of flag leaf angle were detected in 3 different growing environments. They located on chromosome 2,3 and 9. qIFLA-9 was detected in E1 and E2 environments, which located near C506 on chromosome 9, explained 10.35% and 19.08% of phenotypic variance. Positive alleles came from Nipponbare. qIFLA-2 was detected in E2 environments, which located between G275 and C560 on chromosome 2, explained 10.66% of phenotypic variance. Positive alleles came from Kasalath. qIFLA-3 was detected in E3 environments, which located between C25 and C515 on chromosome 3, explained 18.55% of phenotypic variance. Positive alleles came from Kasalath.3. One hundred and three pairs of polymorphyic SSR primers were found betweenⅡ-32B (P1) and A7444 (P2), by amplying the total DNA from the two parents among 238 pairs of SSR primers amplified. The rate of polymorphism was 43.3%. With the 103 SSR markers, SSR marker genotypes of the 158 plants were identified. Heterozygosity marker genotype and homozygous marker genotype ofⅡ-32B consistent with the 1:1 overall segregation Seven markers occurred segregation distortion. The recurrent parent genetic material response rate ranged from 57.77%～88.35%, with an average of 74.39% for 158 plants.Use JoinMap 3.0 software was employed to construct genetic linkage map.The genetic map containing 17 linkage groups and 96 information loci has a total distance of 786.6 cM, averaging 8.2 cM between two loci. Flag leaf angles were investigated at heading stage. we detected QTLs of flag leaf angle by using composite interval mapping method of Win Cartographer 2.5 software, at 5% probability level of genome-wide type I error. Four QTLs of flag leaf angle were detected. They located on chromosome3,4,6 and 8. qFLA-3x located between RM135 and RM448 on chromosome 3, for the nearest marker RM135 12.01cM, positive alleles came from A7444, and explained 11.68% of phenotypic variance. qFLA-4 located between RM3288 and RM6250 on chromosome 4, for the nearest marker RM6250 0.40cM, positive alleles came from A7444, and explained 5.89% of phenotypic variance. qFLA-6 located between RM314 and RM136 on chromosome 6, for the nearest marker RM136 9.68cM, positive alleles came from A7444, and explained 10.82% of phenotypic variance. qFLA-8 located between RM3309 and RM506 on chromosome 8, for the nearest marker RM506 0.01cM, positive alleles came from A7444, and explained 7.77% of phenotypic variance.

Mapping of Flag Leaf Angle QTLs in Rice (Oryza Sativa L.)

Abstract

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