Combined ufra + blast (Bl) infection in deepwater rice [India]
1988
Rathaiah, Y. (Regional Agricultural Research Station, Titabar, Jorhat District, Assam (India))
Ufra disease caused by the stem nematode Ditylenchus angustus is spreading rapidly in the deepwater rice areas of Jorhat District, Assam [India]. Ufra symptoms were severe in the deepwater rice variety Kekua. The panicles failed to emerge, remaining completely choked within the boot. The swollen boot looked like a long spindle. (This type of symptom is termed swollen ufra). Dark brown elliptical lesions appeared on the boot leaf sheaths of swollen ufra stems. The lesions on the boot spread linearly, reaching up to 1 cm, and were slightly sunk lengthwise to become boat-shaped. The lesions turned ash gray in the center with fungus sporulation. Bl fungus Pyricularia oryzae was consistently isolated from the growing edges of the lesions. Stem nematode was extracted in large numbers from the swollen boots that had Bl lesions. Typical Bl lesions also were present on the flag leaf and the second youngest leaf of swollen ufra stems. Bl lesions were common on the collars. Nodal Bl also was seen on many stems showing ufra symptoms. The pathogenicity test with the fungus on detached ufra-infected stems proved Bl. The unusual occurrence of Bl on the leaf sheath may be due to alteration of plant physiology caused by the ufra nematode.
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