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Pakistan Journal of Biological Sciences

Year: 1999 | Volume: 2 | Issue: 3 | Page No.: 849-854
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Authors

Fokunang C.N

C.N.Akem

T.Ikotun

A.G.O.Dixon

E.A.Tembe

Keywords

Research Article

Seed Survival and Transmission of Cassava Anthracnose Disease, and Seed Treatment Effect on Seedling Growth

Fokunang C.N, C.N.Akem, T.Ikotun, A.G.O.Dixon and E.A.Tembe
Open pollinated seeds from cassava genotypes were used to investigate the survival and transmission of cassava anthracnose disease fungus. Seeds from each genotype were surface- sterilized, cultured on potato dextrose agar (PDA), and incubated for 8 days, at 25±2°C. Microscopic examination indicated that Colletorichum gloeosporioides was one of the seed-borne fungi, with up to 40 per cent incidence in some genotypes. Seeds from five genotypes with high incidence of C. gloeosporioides, were selected for transmission studies. They were planted in steam-pasteurized soils in jiffy pots in the greenhouse. The pots were placed closed to each other to increase canopy relative humidity needed for anthracnose development at temperatures of 25-32°C. After six weeks, some plants exhibited symptoms that resembled those of cassava anthracnose disease. The stems, leaves and roots of these plants were washed, surface sterilized, plated on PDA and incubated for 5-7 days. Microscopic examination of the fungus identified conidia of C. gloeosporioides. The rest of the plants were monitored for 3 months under vector-free conditions for typical anthracnose symptoms. Mean maximum wilt and defoliation of 35-38per cent was recorded on some genotypes. C. gloeosporioides f. sp. manihotis was confirmed by pathogenicity tests on young healthy cassava seedlings with stem puncture inoculations. Treatment of infected seeds with three synthetic fungicides; benlate, captan, thiram, two anti-microbial plant products from Azadirachta indica A. Juss and Ocimum gratissimum Linn at full strength concentration, and hot water treatment, significantly reduced fungal incidence, increased seedling emergence and plant vigour index of the cassava genotypes.
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