Disease control and plant growth promotion (PGP) of selected bacterial strains in Phaseolus vulgaris

Abstract

The aim of this study was evaluating the effect of Rhizobium (RE10 and RM02) and Bacillus (B02 and B15) strains to reduce the incidence of disease caused by Sclerotinia sclerotiorum as well as to improve the yield of common bean cv. Centenary plants in field trial. The field trial was located in Pachacamac, Lima, Peru, and consisted of 8 treatments arranged in a random block design with three replicates. For the chemical control, different fungicides were applied on seeds and leaves. For each treatment, bacteria were first inoculated on the seeds and thereafter inoculated three times more in the plant neck. The seeds were pelleted with bacterial suspension (108 CFU/ml) previously mixed with 1 g of agricultural soil. The plant neck was sprayed with 6 ml of 2 × 105 CFU/ml, in three stages of crop growth. At harvest time, all the inoculated treatments showed the lowest percentage of plants infected by the disease caused by S. sclerotiorum with significant difference compared with untreated plants (14 %). The best treatment was RE10 + B02 (2 %), followed by RM02 (3 %) and B02 (4 %) without significant difference compared with the chemical control (2 %). The same strains also showed the highest percentage of germination. Treatment RE10 + B02 also presented the highest yield (16 pods/plant and grain yield of 1717.8 kg/ha) with significant difference compared with untreated plants (11 pods/plant and 883.2 kg/ha). On the other hand, plants inoculated with Rhizobium strains presented between six and ten nodules per plant, while untreated plants presented less than four.