Abstract
In order to examine the susceptibility of the Oryzae to the blast fungus 92 strains of 20 species belonging to the genus Oryza, 3 interspecific Oryza hybrids, 2 strains of Zizania latifolia, and a strain of Chikusichloa aquatica were tested in a greenhouse with 2 isolates of Piricularia oryzae, namely P-2 and 54-04. The plants were grown in Wagner's pots, being fertilized with ammonium sulphate, calcium superphosphate and potassium sulphate. They were inoculated by spraying spore suspensions on the third and fourth leaves, or by injecting the suspensions with a hypodermic syringe into the fifth to seventh still folded leaves. The degree of susceptibility was determined by the degree of lesion formation on the leaves.
The experimental results, in general, showed that the injection method was more efficient than the spraying method, and as to the pathogenicity, the isolate P-2 was more virulent than the isolate 54-04. O. sativa f. spontanea, O. perennis, O. barthii, O. stapfii, and O. breviligulata, which are closely related to the cultivated rice, exhibited either resistance or susceptibility to both these isolates of the blast fungus, according to strains within a single species. Other plant species which are distantly related to the cultivated rice, generally exhibited susceptibility or a moderate resistance. Zizania latifolia was highly resistant, while Chikusichloa aquatica showed susceptibility. Any relationships between the susceptibility and locality, chromosome number, or genome formula were not obvious.
