S. Chen et al., Improving bacterial blight resistance of '6078', an elite restorer line ofhybrid rice, by molecular marker-assisted selection, PLANT BREED, 120(2), 2001, pp. 133-137
Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is on
e of the most devastating diseases of rice world-wide; it is also a serious
problem of hybrid rice production in China. In this study, a molecular mar
ker-assisted introgression of Xa21, a gene highly resistant to a broad spec
trum of Xoo strains, from 'IRBB21' was performed to improve the BE resistan
ce of '6078', a new restorer line with high yielding potential. The entire
process took one generation of crossing followed by three generations of ba
ckcrossing and one generation of selfing. The presence of Xa21 in each gene
ration was determined by both polymerase chain reaction (PCR) and pathogen
inoculation. Recombinations between Xa21 and flanking markers were identifi
ed by PCR analysis. Background selection was conducted in BC1F1 and BC2F1 u
sing amplified fragment length polymorphism (AFLP) markers detecting a tota
l of 129 polymorphic bands between '6078' and 'IRBB21'. The individual sele
cted in BC3F2, or '6078'(Xa21), carried a fragment of less than 3.8 cM from
the donor line in the Xa21 region on chromosome 11, and about 98.8% of the
generic background from the recurrent parent. The results showed that '607
8'(Xn21) had the same level and spectrum of BB resistance as the donor pare
nt 'IRBB21', while maintaining the agronomic performance and combining abil
ity of the original 6078. A significant increase in BE resistance was also
achieved in the hybrid using 6078(Xa21) as the restorer line.