Race identification and Distribution of Bean Anthracnose(Colletotrichum Lindemuthianum) in major Bean growing areas of Zambia
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A study to determine the distribution and relative importance of bean anthracnose( Colletotrichum lindemuthianum) and to identify and characterize races of this fungus in the major bean production areas of Northern, Luapula and North western provinces of Zambia was conducted in 2004. The study was conducted in three stages that involved a field survey and two experiments, one in the field and the other in the laboratory. The objective of the study was to gain information on the type of anthracnose races prevalent in Zambia and magnitude of their virulence in order to develop appropriate and sustainable control strategies by way of breeding for resistant varieties for adoption by resource–poor farmers. The survey was employed to collect disease samples and determine the severity and incidence in Kasama ,Mbala, Mpika, Samfya, Mansa, Solwezi and Mwinilunga districts. Anthracnose fungus was found distributed in all growing areas with medium to high severity in 76 percent of the 90 fields surveyed. Angular leaf spot, common bacterial blight and rust were the other diseases found distributed in the target areas in descending order of frequency. Anthracnose was most severe in Mwinilunga while incidence was highest in both Mbala and Mwinilunga districts. All local landraces in the target area were susceptible to anthracnose attack. The work identified 14 different races of Collectotrichum lindemuthianum based on the 12 CIAT standard differential cultivars from 22 isolates collected from different production areas. Race determination results confirmed that there was great variability of anthracnose fungus in Zambia. Physiological races in Mansa and Mwinilunga showed closer similarities among themselves while race 65 and 73 resembled those characterised in North America. The majority of the races attacked cultivars of Andean origin though some race-specific resistance was found in genotypes from both centres of phaseolus vulgaris origin. Exotic accessions Tu, AB 136 and G 2333 were resistant to all races of anthracnose characterized in the study both in the field and laboratory experiments. Eighteen genotypes tested in the field revealed that anthracnose attack was significantly higher (P≤ 0.05) at flowering and podding stages of bean development at Mutanda Research station (12o25.88 S and 26o12.59 E). The study provided some essential information needed to develop effective breeding and /or crossing programs against bean anthracnose fungus that exhibit high pathogenic variation. It is therefore imperative that gene deployment and pyramiding are employed together with other available methods as sustainable control strategies in order to maximize losses inflicted on the bean crop.
- Agricultural Sciences