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HISTOCHEMICAL STUDIES ON THE LESIONS OF RICE BLAST CAUSED BY PIRICULARIA ORYZAE VAC. PART I. SOME OBSERVATIONS ON THE SPORULATIONS ON LESIONS OF DIFFERENT TYPES OCCURRING ON LEAVES OF THE SAME VARIETY
ARMY BIOLOGICAL LABS FREDERICK MD
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. 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 purpose, 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 hours 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.
Trans. from Nihon Shokubutsu Byori Gakkaiho (Japan) v17 n1 1952.
Approved for public release; distribution is unlimited. Document partially illegible.