Reaction of green gram genotypes to selected fungal and viral diseases in central Uganda

Abstract

Green gram production is mainly constrained by diseases such as Cercospora leaf spot, Mung bean yellow mosaic virus and the powdery mildew. There is diversity in green gram germplasm grown by farmers in Uganda but with limited information on their resistance to Cercospora leaf spot, Mung bean yellow mosaic virus and powdery mildew. Use of resistant varieties is the only affordable, sustainable and environmentally friendly approach to manage these major diseases. However, no comprehensive study has been done in Uganda on the resistance of the different green gram genotypes to Cercospora leaf spot, powdery mildew and Mung bean yellow mosaic virus. The objective of this study was to determine the resistance of green gram genotype to Cercospora leaf spot, powdery mildew and Mung bean yellow mosaic virus (MYMV). A field experiment was conducted at Makerere University Agricultural Research institute Kabanyolo (MUARIK). The experiment was set in RCBD design. Sixteen genotypes were evaluated. Data was collected on disease incidence and severity. Severity was determined by scoring using scale of 0-9 for Cercospora leaf spot and MYMV, and 0-5 for powdery mildew. Data was subjected to analysis of variance using Genstat statistical package (version, 14). Analysis of variance revealed that incidences of MYMV and powdery mildew diseases were significant between genotypes (P ≤ 0.05). Cercospora leaf spot incidence not significant between genotypes (P > 0.05). Severities of the Cercospora leaf spot, powdery mildew and Mung bean yellow mosaic virus diseases of green gram were significant between both genotypes and days after sowing (P ≤ 0.01). Powdery mildew occurred late in the season (at 63 days after sowing). Severity scoring revealed that none of the green gram genotypes was resistant to Cercospora leaf spot and Mung bean yellow mosaic virus. Eight of the genotypes were moderately resistant to (HT5A, HT18A, HT18B, HT18R, HT19B, HT24B, HT25 and HT36B) MYMV. Fourteen of the genotypes were resistant to powdery mildew (TH5A, HT5B, HT17, HT18A, HT18B, HT18R, HT19A, HT19B, HT24A, HT24B, HT25, HT35B, HT36A, and HT36B) while two genotypes (HT33 and HT35B) were moderately resistant to powdery mildew. The findings of the study revealed that green gram genotypes reacted differently to the three diseases they were screened. The genotypes showing resistance and moderate resistance to powdery mildew and MYMV respectively should be evaluated in other regions of Uganda (eastern, north eastern, and northern regions) for consistency of the results and be used for future crop improvement program of green gram. Genotype HT36B should be used as check genotype since it showed promising results during this first evaluation.