Bacterial Blight (Xanthomonas axonopodis pv. phaseoli) Tolerance in Bean Varieties in Zimbabwe

Abstract

Bacterial blight disease of common bean has devastating effects on the production of bean varieties among smallholder farmers in Zimbabwe. Bacterial blight disease caused by the bacterium Xanthomonas axonopodis pv. phaseoli causes substantial yield losses in the smallholder sector hence the need to conduct the study to determine bacterial blight tolerance levels in bean varieties. The different bean varieties belong to different classes namely Ex Rico Navy (small white canning variety), Bonus (Sugar bean variety), Natal sugar (brown speckled bean variety), White kidney (large white kidney variety) and Carioca (Carioca class). The objectives of the study were to determine the different levels of tolerance in the five bean varieties and to prove the existence of bacterial blight tolerance traits in the white bean varieties. The study was carried out at Africa University Research Block located at Africa University Farm in Mutare. The study commenced on 28 February 2012 and was completed on 10 May 2012. Data on disease severity was collected from the field trials. The data was recorded as scores based on the CIAT scale. The average scores for each of the three replications of the varieties was subjected to ANOVA analysis using MINITAB version 13 software. Results of the study showed that Ex Rico Navy was the most tolerant and was significantly different from the other four varieties with an AUDPC of 14.35cm2. Bonus variety was the second most tolerant with an AUDPC of 73.85cm2 followed by Natal Sugar with an AUDPC of 102.78cm2. Carioca with an AUDPC of 128.66cm2 and white kidney variety with an AUDPC of 130cm2, were not very significant from each other and had the least tolerance to bacterial blight. Farmers should make use of the bacterial blight tolerant varieties such as Ex-rico. Research institutes and plant breeders should manipulate the bacterial blight tolerance genes in the white bean varieties and insert them in other bean varieties of other classes for varietal diversity.