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Genetic analysis of
resistance to rice blast (Magnaporthe grisea) of the lines Tres
Marias and 75-1-127
J. Magia
Magnaporthe grisea
is the major destructive pathogen in rice crops. Host resistance is the
most indicated method to control this fungus. This method is hindered by
frequent new strains of the fungus that can overcome the newly released
resistant varieties. Genetic resistance of two rice lines, Tres Marias and
75-1-127, was studied using three races belonging to the major lineages of
Colombia, Fanny 54, Isolinea 6-7-1 and Oryzica caribe 8-17. Analysis of
the segregation ratio between susceptible, intermediate and resistant
plants revealed 1) resistance of the line Tres Marias to Isolinea 6-7-1
and Oryzica caribe 8-17 isolate is controlled by a single dominant gene,
2) resistance to Fanny 54 isolate could be governed by many genes, 3) a
strong genetic correlation between resistance to Isolinea 6-7-1 and
Oryzica caribe 8-17 suggests that the same gene acts against both isolates
or that the genes controlling these isolates are linked, 4) a recessive
and a dominant gene control the pathogenecity of Fanny 54 and Isolinea
6-7-1 isolates and two dominant genes conferred resistance to Oryzica
caribe 8-17 and 5) independent segregation among each pair of isolates
revealed resistance to Fanny 54 is significantly
similar to that of Isolinea 6-7-1 and either the same resistance genes are
effective against both isolates or both loci are linked.
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