Performance of soybean genotypes (Glycine Max L.) against Asian rust (Phakopsora Pachyrhizi Syd.) in Cameroon

Asian rust caused by Phakopsora pachirhizi, which is a major constraint to production of soybean, causing 90% yield losses in field. Synthetic fungicides used to control this disease are environmentally degrading and have negative impact on the health of producers and consumers. The use of resistant soybean genotypes can be an effective control alternative. The aim of this work is to evaluate the tolerance of soybean varieties to Asian rust disease under natural conditions. Forty-three soybean varieties were screened using a completely randomized block design with three replicate. Incidence and severity of disease at 6, 8 and 10 weeks after sowing (WAS) and yields were evaluated. Results show that disease incidence of Asian rust was significantly higher in the local variety R3 (16.67%; 29.63%; 75.93%) at 6, 8 and 10 WAS respectively. At 6 and 8 WAS severity of disease was higher in local variety R3 (21.17% and 24.14% respectively). The variety TGX-2010-12F has the highest yield (1.17 t ha-1) than the local variety R3 (0.17 t ha-1). Principal component analysis realized with incidence, severity of disease at 6, 8, 10 WAS and yield shows that 12 varieties are highly susceptible to Asian rust, 12 varieties are moderately resistant, and 19 varieties are susceptible. This study shows that Asian rust attacks all soybean varieties in the field. Moderately resistant varieties, can be advised to growers with appropriate protection methods or be subject to varietal improvement through genetic techniques.