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African Cereal Streak, a New Disease of Cereals in East Africa. D. E. Harder, Plant Pathologist, University of Manitoba-Canadian International Development Agency, Plant Breeding Station, Njoro, Kenya, Present address is c/o Canada Agriculture Research Station, 25 Dafoe Road, Winnipeg, R3T. 2M9, Manitoba, Canada; W. Bakker, Plant Virologist, National Agricultural Laboratories, Nairobi, Kenya, Present address: Laboratory of Virology, State Agricultural University, Wageningen, The Netherlands. Phytopathology 63:1407-1411. Accepted for publication 14 May 1973. DOI: 10.1094/Phyto-63-1407.

A new disease of small-grain cereals in East Africa is reported. The disease is caused by a spherical virus, which is 24 nm in diam, limited to the phloem, induces phloem necrosis, and is transmitted by the delphacid planthopper, Toya catilina. The proposed name of the disease is “African cereal streak”, and its causal pathogen African cereal streak virus (ACSV). ACSV has been successfully transmitted in the greenhouse and growth chamber to wheat, oats, barley, rye, triticale, rice, Eragrostis chalcantha, E. tenuifolia, Chloris pycnothrix, Aristida adoensis, and Harpachne schimperi. Attempts to transmit it to maize and linseed were unsuccessful. The main symptoms are faint chlorotic streaks originating at the base of the leaf, elongating to form broad bands of alternate yellow and green streaks. Young infected plants remain severely stunted and die prematurely. The inflorescence becomes yellow, and awned types in particular become distorted. Seed yield is almost completely suppressed. The possible relationships of ACSV to other viruses affecting the Gramineae are discussed, as well as some observations with epidemiological implications.