Bls1

Annotated Information

Figure 1. (from reference) .

Figure 2. (from reference) .

The rice bacterial leaf streak (BLS)which has seriously constrained the rice production in humid tropical and subtropical areas of Asia and Africa.When rice is infected by the BLS pathogen, leaves become yellow or even blasted, the rate of unfilled grains will increase, and the grain weight will decrease. In recent years, some QTLs for BLS resistance have been mapped on rice genome using molecular markers.

Function

bls1, a BLS-resistance gene, from a rice line DP3, derived from the wild rice species Oryza rufipogon Griff . The quantitative trait locus (QTL) qBlsr5a has been proved to have the largest effect on the resistance to rice bacterial leaf streak . Li et al. 2008 have analyzed total proteins of leaves of rice cultivar 9311 which had been inoculated by ‘89773-1-1’, a kind of Xooc with strong pathogenicity, in order to find out some proteins associated with the resistance to this pathogen .They found that these proteins are involved in many resistant reactions associated with signal recognition and transduction, cell-wall reinforcement and biosynthesis of phytoalexins, etc.

Expression

According to the research, the BLS resistance in DP3 was controlled by recessive gene(s). To further confirm the inheritance pattern of BLS resistance, BC2F2 (9311/DP3//9311) populations were evaluated by JZ-8 strain inoculation. The damage severity scores of 307 individuals in BC2F2 population ranged from 0 to 9, and showed a pattern of bimodal distribution (Fig. 2). The segregation of resistant and susceptible plants well fitted in 1:3 ratio , suggested that a recessive gene, tentatively designated as bls1, conferred BLS resistance in DP3 .

Evolution

The common wild rice (O. rufipogon Griff.) is considered as wild ancestor of cultivated rice. The wild rice species with AA genome has been well recognized as a primary gene pool that conserves a lot of specific genes such as genes resistance to grassy stunt virus from annual wild rice . It is believed that the frequency of resistance genes in wild rice is 50 times higher than that in cultivated rice because it has undergone a long history of natural selection and contained rich genetic diversity .

Location

The linkage map of the bls1 gene was made in a compact region on chromosome 6. The most closely linked markers flanking the bls1 gene were RM587 and RM510 with genetic distances of 2.9 and 1.1 cM. The BLS resistance gene, bls1, was mapped and confirmed in a narrow region flanked by RM587 and RM510 on chromosome 6 (Fig. 3). Therefore, these two closely linked markers, RM587 and RM510 may be used for marker assisted selection (MAS) of BLS resistant lines in rice breeding.(1) By genotyping these homozygous individuals with SSR markers and performing linkage analysis, qBlsr5a was mapped to an interval between SSR markers RM153 and RM159, which covered a range of 2.4 cM or 290 kb .

Figure 3. (from reference) .

achievements on this gene

• Earlier studies on the inheritance of resistance to BLS in other cases also suggested some types of resistance to BLS are controlled by major genes (Zhang et al. 1996; Xu et al. 1997; Zhou et al. 1999; Zhao et al.2004).
• The BLS resistance in rice has been proved to be a quantitative trait controlled by polygenes. (Zhang et al. 1992; Khush 1977; Gnanamanickam et al. 1999; Tang et al. 2000)
• Some major BLS resistance genes have also been identified (He et al. 1996; Zhang et al. 1996; Xu et al. 1997; Zhou et al. 1999).
• 3 QTLs have been identified which confered the BLS resistance in rice. (Tang et al. 2000)
• In China, Peng et al. (1982) found that the wild rice has high resistance to BLS.
• Xu et al. (1991) screened 2 017 rice accessions, which were derived from the generations of wild rice species, and identified 30 accessions highly resistant to BLS. Huang et al.(2008) also identified 57 resistant accessions from 1655 accessions of wild rice resources.