Evaluation for drought tolerance and anthracnose resistance of selected pinto genotypes of common bean (phaseolus vulgaris l.).
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Date
2023
Authors
Mwense, Brian Pule
Journal Title
Journal ISSN
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Publisher
The University of Zambia
Abstract
Common bean (Phaseolus vulgaris L.) is an important legume crop grown for household revenue, food and nutrition security in many parts of the world. Common bean is classified into Andean and Middle American gene pools. Most of the beans grown in east and southern Africa countries including Zambia are Andean. In the recent years there has been interest in Zambia in growing pinto beans, which is a major Middle American market class especially in the US, but new to Zambia and most other African countries. The adaptation of pinto beans to Zambia isn’t well established especially that the country is prone to drought and anthracnose disease. Anthracnose is the most important disease of common bean in Zambia, which is likely to affect production of this market class in a similar way it has affected other currently grown market classes. Additionally, drought has become an increasingly important production constraint because of frequent drought episodes in bean growing areas caused by climate change. Furthermore, production of common bean has been expanding to geographical areas that are prone to drought. Identification of pinto beans genotypes that are tolerant to drought and resistant to anthracnose could support production and productivity of pinto beans in Zambia and other African countries. The objectives of this study were: (i) Evaluate the agronomic and morpho-physiological response of selected pinto genotypes to terminal drought, and (ii) Determine the response of selected pinto genotypes to seven races of Colletotrichum lindemuthianum the causative fungus for anthracnose. A total of 56 pinto bean genotypes and 4 checks were evaluated for tolerance to drought and resistance to seven races of C. lindemuthianum. Evaluation for drought tolerance was conducted using one pot experiment and two field trials. For the pot experiment, Electrolyte leakage and canopy temperature depression was measured on the 56 pinto genotypes and 2 checks grown under drought stress (DS) and Non-Drought stress conditions. The two field trials for drought tolerance were conducted at the University of Zambia (UNZA) and Golden Valley Agriculture Research Trust (GART) Research farms under drought stress and non-stress conditions. The primary traits measured included pod number, shoot dry weight, seed weight and seed yield. The traits computed from these primary traits were harvest index (HI), pod harvest index
(PHI), yield geometric mean (GM) and yield percentage reduction (YPR). There were significant differences among 56 genotypes in all primary and computed traits indicating significant genetic differences in their response to drought. The average YPR for GART and UNZA were 43.6% and 58.5%, respectively. The genotypes with highest GM at GART and UNZA were NDZ14048-5 (1,200 kg ha-1 ) and NDZ14048-2 (1,331 kg ha-1 ), respectively. Seed yield was significantly correlated to PHI (r=0.55***) and HI (0.68***) under DS suggesting the important role that these two partitioning indices played in the observed drought tolerance for some of the genotypes. Therefore, PHI and HI can be used to indirectly select for drought tolerance. The genotypes NDZ14048-2 and NDZ14048-5 were particularly outstanding in their seed yield performance under both DS and NS conditions. The 56 pinto genotypes and checks were evaluated for resistance to races 51, 65, 73, 247, 253, 263 and 1085. Significant differences were observed among the 56 pinto genotypes in their reaction to seven races of Colletotrichum lindemuthianum. In general, the reaction of the 56 genotypes was skewed towards susceptibility except for races 51 and 73. There was no genotype that was resistant to all seven races. In general, the genotypes that showed resistance to most of the races were those that carried Co-4 2, which highlighted the importance of this locus to anthracnose resistance. The three genotypes NDZ14006-4, NDZ14110-4 and NDZ14043 showed superior resistance among the 56 pinto genotypes used in the current study as each was resistant to six of the seven races used in the current study. The genotypes NDZ14048-2 and NDZ14048-5 which showed superior seed yield under both DS and NS, and carry the Co-4 2 anthracnose resistance loci were resistant to five of the seven races used in the current study. The combination of high seed yield (under both DS and NS) and anthracnose resistance exhibited
by NDZ14048-2 and NDZ14048-5 make them ideal for use to enhance the adaptation of pinto beans to anthracnose and drought.
Description
Thesis of Master of Science in Agronomy.