Abstract
The fragrant rice breeding has become an important direction for hybrid rice breeding program. The selection and utilization of parent materials with ideal plant type, fine grain quality, strong resistance and other excellent agronomic characteristics with strong fragrance, especially the utilization and cultivation of the fragrant rice restorer lines, is of great significance to further promote the fragrant hybrid rice breeding. Taiguoxiaoxiangzhan is a restorer line with excellent grain quality, strong resistance and fragrance, which has been widely used in fragrant rice breeding in China. In order to trace the fragrance in Taiguoxiaoxiangzhan, we identified the type of the fragrance gene in Taiguoxiaoxiangzhan was badh2-E7 which has an 8 bp deletion and three single nucleotide polymorphisms (SNPs) in exon 7, and this gene is a non-functional badh2 allele and that the functional Badh2 allele encoding betaine aldehyde dehydrogenase (BADH2) could render rice non-fragrant. Furthermore, we found that the Taiguoxiaoxiangzhan increased 2-acetyl-1-pyrroline (2-AP) content (0.108 mg/kg) compared with the non-fragrant rice varieties of Nipponbare and 9311 (<0.01 mg/kg) by the GC-MS method. We also proved that FMbadh2-E7 and InDel-E7, two molecular markers reported earlier, can be applied in different genotypes, including Badh2/Badh2 (non-fragrance homozygote), Badh2/bahd2 (non-fragrance heterozygote) and badh2/badh2 (fragrance homozygote). In addition, based on sequence divergence amongst the functional Badh2 and null badh2-E7 allele, we developed two functional markers, FMbadh2-E7A and FMbadh2-E7B, which can be easily used to distinguish non-fragrant from fragrant rice. Genetic analysis shows that the segregation of Badh2/Badh2 , Badh2/badh2 and badh2/badh2 in the F 2 population derived from crosses between Taiguoxiaoxiangzhan and different restorer lines fitted a theoretical ratio of 1:2:1, indicating that the fragrance of Taiguoxiaoxiangzhan is controlled by a single nuclear recessive gene ( bahd2 ). In this study, the identification and genetic analysis of the fragrance gene in Taiguoxiaoxiangzhan and the development of functional markers for fragrance have been studied, which provides a theoretical foundation for the further breeding of fragrant hybrid rice with excellent quality, high yield and strong resistance by molecular marker-assisted selection technology.
Highlights
The fragrant rice breeding has become an important direction for hybrid rice breeding program
In order to trace the fragrance in Taiguoxiaoxiangzhan, we identified the type of the fragrance gene in Taiguoxiaoxiangzhan was badh2-E7 which has an 8 bp deletion and three single nucleotide polymorphisms (SNPs) in exon 7, and this gene is a non-functional badh2 allele and that the functional Badh2 allele encoding betaine aldehyde dehydrogenase (BADH2) could render rice non-fragrant
The results showed that the type of the fragrance gene in Taiguoxiaoxiangzhan was badh2-E7 which has an 8 bp deletion and three single nucleotide polymorphisms (SNPs) in exon 7 (Figure 1B)
Summary
The fragrant rice breeding has become an important direction for hybrid rice breeding program. A variety of methods have been established to detect the fragrance of fragrant rice materials, including the most common methods in traditional breeding process, such as chewing method, coloration method and KOH soaking method (Yan et al, 2015; Peng et al, 2017) These methods mainly rely on human senses to identify and evaluate the fragrance, so it is difficult to ensure the accuracy and reliability of the results, and it is impossible to carry out quantitative analysis. Mutations in the coding region or regulatory region of the Badh gene can lead to the loss of function of the gene, which makes the rice produce strong fragrance
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