Vol. 20 >B. Research Notes>V. Genetics of disease and insect resistance |
43. | Resistant genes and their effects to rice blast in isogenic lines of genetic background of Chucheongbyeo and Suweon345 |
Y.C. CHO1, I.S. CHOI1, M.K. BAEK1, J.P. SUH1, H.C. HONG1,
Y.G. KIM1, S. KOIZUMI2, K.K. JENA3, H.C.CHOI1 and H.G. HWANG1 1) National Institute of Crop Science, RDA, Suwon 441-857, Rep. Korea 2) National Agriculture Research Center, Kannondai 3-1-1, Tsukuba, Ibaraki, 305-8666, Japan 3) IRRI-Korea Office, National Crop Experiment Station, RDA, Suwon 441-857, Rep. Korea |
Rice blast caused by the fungus Magnaporthe grisea is one of the
most destructive diseases of rice. The development of resistant cultivars
is potentially the most effective and economical method of controlling
blast disease. Although, many rice cultivars with complete resistance
have been developed, most of resistance were broken within a few years
after cultivar release as a result of the differentiation of new races
of rice blast fungus. The use of multilines was suggested as a means to
prevent the breakdown of the resistance to disease. Nearisogenic lines
with different complete resistance genes to blast have been reported by
many researchers in Japan. The recurrent parent Chucheongbyeo was known to have the Pia gene
for blast resistance, but the effectiveness of this gene to leaf blast
was low in the field in Korea. Two resistant genes Pia and Pik-m
were identified in donor parent Bongkwangbyeo. Seolagbyeo was developed
from a cross between BL1 (having Pib and Pish genes) and
Fuji280 (having Pia and Pita-2). The third donor parent
Daeseongbyeo was developed from the cross Bongkwangbyeo x Fuji280. All
isogenic lines in the Chucheongbyeo genetic background are likely to have
the Pia gene from Chucheongbyeo, because the chromosomal region
containing this gene was monomorphic for the flanking markers RM441 and
RM552 in the isogenic lines and the parent. Isogenic line M7 was shown
to have genes Pita and Pi25(t), M28 to have Pi5(t)
and Pi44(t), M64 to have Pi44(t), and M94 to have Pi10(t)
with Pia. M85 and M88 developed from donor Daeseongbyeo would contain
Pi7(t) and Pi25(t). The region on chromosome 12 in which
Pita and Pi25(t) are located is also the site for the clustering
of many other resistance genes such as Pita-2, Pi4 and Pi12(t).
The Pi5(t) gene of isogenic line M28 may be the same gene as Pii,
because Pi5(t) is in the same 170kb genomic segment as Pi3(t)
(Jeon et al., 2003), which is allelic or closely linked with Pii
gene. In summary, the resistance genes carried by the isogenic lines in
the Chucheongbyeo background would be Pia, Pita, Pi5(t)
and Pi25(t); there is also a need to screen more markers flanking
Pi7(t) and Pi44(t).
field (Table 4). In the case of leaf blast, four multilines had the effect
of reducing the incidence of disease when compared with their recurrent
parents. In the case of neck blast, the incidence of disease was reduced
ten-fold in Suweon433-I and two-fold in Suweon443-I. Although multiline
Suweon443-I had the effect to reduce the incidence to neck blast, it was
over 10% on the average. Because neck blast causes an immediate loss of
yield, it is important to develop rice varieties with resistance to this
disease. It is interesting that isogenic lines of Chucheongbyeo containing
the Pia gene were more effective in field resistance, especially
to neck blast, than those isogenic lines of Suweon345 containing Pib
gene. We infer that it is more important to combine the right kinds of
genes than a particular number of genes. In summary, there is a need to
test the allelic relationships for the inferred genes, and to identify
those combinations of genes that are effective in enhancing for broad-spectrum
and stable resistance for blast. |
Vol. 20 >B. Research Notes>V. Genetics of disease and insect resistance |