1953 Volume 17 Issue 1 Pages 1-4_1
Leaf lesions of blast, caused by Piricularia oryzae, on a susceptible variety of rice were grouped into five classes according to the degree of brown coloration and size of the lesions (see Fig. 2)
Sporulation process on a single lesion of class 4 was observed and microphotographed at definite intervals. After a lesion was placed in a moist chamber, specially designed for the present purposs as shown in Fig. 1, a conidiophore began to emerge in about six hours, and produced the first conidium at its apex one hour later which reached its full size in 40 minutes. Soon after, a branch developed from the conidiophore just below the point of attachment of the first conidium, and the second conidium was formed at its apex.
In the same manner, process of conidial formation continued to form 7 to 9 conidia on one conidiophore, each being formed at about an hour's interval. The mode of branching of the conidiophore is sympodial in accord with the observations of Henry et al. (1948).
Sporulation intensities of lesions of different classes were compared. Sporulation was most rapid and abundant on 4, less on 5 and 3, and very scarce in 2, whereas entirely absent on 1. It seems likely that the browning of the lesion could retard the spread and normal growth of the mycelia in the host tissue, and, consequently, the sporulation on the lesion.
(National Institute of Agricultural Sciences)
