Screening of plant growth-promoting rhizobacteria in watermelon

Abstract

The plant growth-promoting bacteria (PGPB) have been found attached to the ground or colonizing the surface of roots in many crops increasing their yield. The aim of this study was to characterize bacterial strains from the rhizosphere of  cucurbits and assess their effect on development of watermelon seedlings cv. Crimson Sweet. The strains were isolated and evaluated to the phenotypic characterization and grouping by UPGMA method based on coefficient of Bray-Curtis. The treatments consisted of 44 bacterial strains and the control using a completely randomized design with five replicates. Each strain was inoculated on the seeds with a concentration of 4.5 x 10^-8 CFU.mL^-1 for 24 hours. Controls were immersed in distilled and sterilized water at the same time. In 20 days after sowing, it was evaluated the length and dry weight of root and shoot. The data were submitted to variance analysis and the averages compared by the Scott-Knott test at 5% of significance level. The dendrogram of the 44 strains showed the formation of 29 clusters with similarity of 80%. The strain UNEB 55 provided an increase in the length and dry weight of shoots and roots of watermelon. The strains UNEB 05, UNEB 27, UNEB 53 and UNEB 57 induced increase in the length of the shoot without deleterious effect on other variables. These results indicate that these strains may be used as plant growth-promoting bacteria in watermelon.