The use of host resistance in disease management of rust in common bean

Abstract

Bean rust, caused by Uromyces appendiculatus, is one of the major diseases in dry and snap bean production world-wide. Numerous advancements in disease management have been made to reduce rust losses. Host resistance is an important component of rust management. However, durability of disease resistance has often been short due to the use of single genes for resistance interacting with extremely high virulence diversity of the bean rust fungus. The challenge to increase durability of resistance has led to strategies such as gene pyramiding of race-specific resistance, selection and use of partial resistance, and investigation and discovery of leaf morphological features that may slow the rust epidemic. Germplasm with multiple sources of rust resistance has been developed in specific bean seed classes and released for public and commercial use in intensive production systems such as those in the United States. However, progress to develop rust resistant germplasm for the subsistence agriculture of Latin America and Africa where intercropping and mixed cultivars dominate the production system has been slow. Incorporation of high yielding, disease-resistant components as partial replacement in farmer's mixtures has the potential to reduce severity in the crop and increase yield in the presence of rust. This strategy would not erode the genetic diversity that is historically known to enhance resistance durability and for many years has given stability in production in the subsistent agriculture systems.

Prevalence and variability of the common bean rust in Uganda

“…These findings confirm the importance of a disease management in small-holder farms. Farmers could also reduce rust disease on their farms by planting resistant varieties (Mmbaga et al, 1996). In this study, rust disease incidence and severity were significantly influenced by the type of bean variety grown (Figure 4).…”

“…The high severity level of sole cropping system may result from the re-infection of the beans fields with rust pathogens from debris or volunteer crops and weeds. High rust severity in sole cropping system has been reported by Mmbaga et al (1996). At f the crop diversity level, the beans-maize-groundnut intercropping system showed the highest disease incidence (100%) while the bean-coffee-banana intercropping system had the lowest score of 2%.…”

“…However, the beans-coffee and beans-maize-groundnut intercropping system showed the highest disease severity of 6 while the bean-coffee-banana intercropping system had the lowest score of 2. Msuku and Edje (1980) reported that the common bean-maize cropping system had reduced rust severity while Mmbaga et al (1996) indicated that intercropping beans and maize affected bean rust epidemiology by influencing spore dispersal, spore retention and infection efficiency. However, the high rust severity in the bean-groundnut and maize intercrop might have resulted in the rust disease buildups in the fields because of the higher relative humidity resulting from the maize-bean-groundnut canopies which favoured uredospore production (Msuku and Edje, 1980).…”

“…Cultural practices were once thought to have only a minimum effect on the prevalence of bean rust (Mmbaga et al, 1996). Lin (2011) suggested that cropping systems such as crop diversification can contribute to the spread or suppression of the disease.…”

“…Liebenberg and Pretorius (2010) reported that cultural practices such as cultivar mixtures, crop rotation, planting time and age of crop, intercropping and choice of bean varieties could affect the level of infection and spread of the rust disease. Mmbaga et al (1996) suggested that airborne rust spores produced on volunteer, wild or cultivated beans are sources of infection that could reduce the effectiveness of crop rotation. Ronner et al (2013) stated that common bean are mostly grown as either as sole crops or as intercrops (on 2/3 rd of the total plots planted with beans) with maize, cassava, cotton, bananas and groundnuts in Uganda.…”