Screening of groundnuts (Arachis hypogaea L.) for resistance to early and late leaf spots

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Groundnut (Arachis hypogaea L.) is an important crop both in subsistence and commercial agriculture in Ghana. Early leaf spot (Cercospora arachidicola) and late leaf spot (Phaeoisariopsis personata) are major limiting factors to groundnut productivity in Ghana. The objective of the study was to determine resistant or tolerant varieties due to combined attack of both diseases. A disease-based questionnaire was administered to 100 farmers in their local language spread across 10 villages and towns selected from Tamale, Tolon-Kunbungu and Savelugu-Nanton Districts, all in the Northern Region of Ghana. The responses of the farmers showed that Cercospora leaf spot (ELS and LLS) is one of the major constraints to groundnut production in the area to which farmers have no solution. The severity of the disease was dependent on the cropping system adopted by the farmers. The variety Chinese turned out to be the most important commercial cultivar grown by farmers but it is susceptible to both diseases. Sixteen local groundnut varieties were field-screened from 2006 to 2008 at the Crops Research Institute, Kumasi, under the Council for Scientific and Industrial Research. The experiment was laid out in randomised complete block design (RCBD) with three replications. Early and late leaf spot ratings were recorded at 40 and 60 days after planting for early leaf spot, and 70 and 90 days after planting for late leaf spot, using a five point scale. The means of the scores were recorded. Pod and grain yields were also recorded at harvest. The results indicated that Azivivi, Nkosour, Adepa, and Jenkar had lowest score of 1.0 for both early and late leaf spot diseases. Among the four groundnut cultivars, Azivivi recorded the highest pod yield of 1086.1kg/ha and grain yield of 713.9kg/ha, followed by Nkosour with pod yield of 1011.7kg/ha and grain yield of 657.2kg/ha. Adepa had a pod yield of 929kg/ha and seed yield of 603.9kg/ha. The pod yield of Jenkaa was 842.2kg/ha and seed yield of 525.6kg/ha. All of them, except Jenkaa, recorded pod yield above 880kg/ha., a national average pod yield of groundnut. From this study, Azivivi, Nkosour, Adepa, and Jenkaa are recommended for cultivation by farmers, since they are resistant to Cercospora leaf spots (ELS and LLS).
A thesis submitted to the School of Research and Graduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the award of Master of Science degree in Crop Protection (plant pathology), 2010