Six isolates of Colletotrichum gloeosporioides f.sp. manihotis obtained from anthracnose-infected cassava stems in six different cassava-growing locations of Akwa Ibom State were examined in the laboratory for morphological and physiological differences. The isolates were then screened in the greenhouse for virulence on cassava variety NR 8083 widely grown in Akwa Ibom State. Six-week old cassava plants were inoculated with 1ml of the spore suspension of each isolate of the pathogen at a concentration of 10 4 conidia/ml using a sterile hypodermal needle. One injection of inoculum was made at five different internodes of each cassava stem at an ambient temperature of 30 0 C and relative humidity of 80%. Results of laboratory examinations showed that mycelial growth on potato dextrose agar (PDA) medium was fastest (10.65mm/day) in isolate CGM 2 from Ikono and slowest (7.29mm/day) in isolate CGM 6 from Uyo. Sporulation of the isolates on PDA medium under alternate light and dark regimes was highest (9.30 x 10 6 spores/ml) in isolate CGM 4 from Nsit Atai and lowest (1.23 x 10 6 spores/ml) in isolate CGM 5 from Oruk Anam. Percentage spore germination and conidia length were highest (85.64% and 23.55µm) respectively in isolates CGM 4 from Nsit Atai and CGM 1 from Essien Udim and lowest (49.86% and 13.75µm) in isolate CGM 3 from Itu and isolate CGM 2 from Ikono, respectively. Results of greenhouse inoculations showed variations in lesion size for the different isolates. The largest (15.30mm) lesion was produced by isolate CGM 4 from Nsit Atai, followed by isolate CGM 1 (12.60mm) from Essien Udim. There were no significant (p> 0.05) differences in lesion size for isolates CGM 3 (8.63mm) from Itu, CGM 2 (8.45mm) from Ikono and CGM 6 (8.41mm) from Uyo. Lesion size was smallest (5.00mm) in isolate CGM 5 from Oruk Anam. Isolate CGM 4 of C. gloeosporioides f.sp manihotis from Nsit Atai which showed the highest sporulation density and percentage spore germination, one of the longest conidia and largest lesion size on inoculated cassava stems, appeared to be the most virulent of the six isolates of the pathogen in Akwa Ibom State during this investigation.
Kernels of three maize varieties namely: Fraz 23, Fraz 34 and Bendel White planted in Eastern Nigeria in 1982 and 1983 planting seasons were screened for seed-borne fungi. The effects of Thioral (a.i. 25% heptachlor and 25% TMTD), a biocidal seeddressing chemical, on seed-borne fungi and on kernel viability were also investigated. Results showed that kernels of the three maize varieties screened harboured Fusarium moniliforme. Fusarium nivale, Fusarium semitectum, Aspergillius flavus. Penicillium oxalicum, Curvularia pallescens, Rhizopus spp. and Saccharomyces spp. at appreciable high percentages. Fusarium species dominated the other fungi. These fungi caused appre-. ciable reduction in the percentage kernels germinating. In Thioral-treated kernels, F. moniliforme, F. Nivale, F. semitectum. P. oxalicum, C. pallescens, Rhizopus spp. and Saccharoymces spp. were completely eliminated or reduced. The percentage kernel germination increased significantly (P = 0.001) and no phytotoxic effects were observed on the kernels' seedlings treated with Thioral. The mean percentage incidence of A. flavus isolated in Thioral-treated kernels increased when compared with the untreated kernels in all the three maize varieties.
Abstract:To investigate the effect of planting date, spacing and seeding methods on disease development and yield components of rice, a factorial experiment in randomized complete block design (RCBD) with four replications was conducted during 2011 planting season at Izzi Local Government Area (LGA) of Ebonyi State, Nigeria. This experiment was carried out with four levels of planting dates (early June, late June, early July and late July), three levels of spacing (15, 20 and 25 cm) and two levels of seeding method (direct seeding and seedling transplanting). The studied traits included plant height (PH), number of tillers (NT), leaf area (LA), root length (RL), panicle length (PL), 1,000 seed weight (SW), disease incidence and severity. The result showed that all the factors had significant effect on the parameters measured. Sowing in early July had the highest LA of 65.38 cm 2 , PH of 122.00 cm, RL of 29.04 cm and TN of 10.54, and the second largest PL of 25.08 cm and SW of 25.12 g. Also sowing in early July had the highest disease severity of 3.21, followed by 3.14 which occurred in late July, while the least 2.17 occurred in early June. The direct seeding method had the highest disease incidence of 70.83%, followed by plant spacing of 15 cm × 15 cm which had the disease incidence of 69.72%, while sowing in early June had the least disease incidence of 57.50%. In conclusion, planting of rice in Southeastern Nigeria should be done in early July, as the yield components were significantly better than in other dates though with the highest disease severity.
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