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University of Nairobi (2014)

Selection For Drought Tolerance, Disease Resistance, Canning And Nutritional Quality In Dry Beans

Warsam, Ahmed Omar

Titre : Selection For Drought Tolerance, Disease Resistance, Canning And Nutritional Quality In Dry Beans

Auteur : Warsam, Ahmed Omar

Université de soutenance : University of Nairobi

Grade : Master of Science Degree in Plant Breeding and Biotechnology (2014)

Résumé
Common bean (Phaseolus vulgaris L.) is the most important legume crop in eastern and central Africa. The crop is low yielding and underutilized due to several factors such as biotic and abiotic stresses and poor seed quality attributes. Therefore, breeders must consider production and utilization constraints when developing new bean varieties. Bean growers want bean varieties to be high yielding and tolerant to production constraints such as drought and diseases. Bean consumers want beans that cook fast and have good sensory qualities. Processors of beans are constrained by the consumer preferences, but they also want beans to meet specific processing standards. In addition, to contribute in fight against micronutrient malnutrition among poor population, new bean varieties should have high nutritional quality. This research was therefore undertaken to identify bean cultivars of different grain types with superior agronomic performance, good culinary, canning and nutritional quality from the available germplasm. Field trials were conducted for two seasons during long-rain 2012 and short-rain 2012/2013. In the first season, 427 lines from seven market classes and local check varieties were planted at Kabete and Thika under irrigated and rainfed conditions in asplit plot design. Selections from the first season were evaluated under rainfed conditions in four sites including Kabete, Nakuru, Thika and Tigoni using 5x5 lattice design. Data on days to flowering, days to maturity, reaction to major diseases under field conditions and grain yield were recorded. Water regimes and site significantly affected days to flowering and maturing of the genotypes. Genotypes matured earliest in Thika and latest in Tigoni. In both seasons, local varieties KATB9, KATB1, GLPx92, GLP1004 and Miezi Mbili were early maturing compared to test lines. During the first season, Kabete experienced severe disease breakout. Anthracnose was the most severe with 24% of the genotypes succumbing to the disease (7-9 score). Red mottled and speckled sugar lines were v affected the most by the disease with over 40% of the genotypes succumbing to the disease. Nearly all local varieties succumbed to the disease. Results showed that Thika site had drier conditions and rainfed plots had 30% less yield compared to irrigated plots. At Kabete, effect of water regime was concealed by the diseases which infected severely the genotypes under both treatments. Lines which performed well under both rainfed and irrigated treatmentsat Thika were selected for drought tolerance during the first season. Most of the local check varieties were low yielding and very susceptible to diseases under different conditions. Mexican142 was the best check in terms of yield and reaction to diseases. One hundred fifty lines were selected and evaluated for cooking time, water absorption and hard-shell defect to identify lines combining good agronomic and culinary traits that are suitable for household preparation and food processing industry. The most agronomically superior variety, Mexican142, was used as control. Mattson bean cooker was used to determine cooking time

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Page publiée le 9 juillet 2014, mise à jour le 30 mars 2018