EFFECT OF SOIL Pseudomonas ISOLATES APPLIED TO CORN, SORGHUM AND WHEAT SEEDS ON SEEDLING GROWTH AND CORN YIELD

Abstract

The purpose of this study was to determine the effect of several Pseudomonas isolates obtained from the rhizosphere of corn (Zea mays L.), sorghum (Sorghum bicolor Moench L.) and wheat (Triticum aestivum L.) on the seedling growth of these cereals and on stalk rot and grain yield of corn. Seeds of BoJac 56 and NC 5288 corn hybrids. Asgrow and Pioneer 8272 sorghum hybrids and Parker 76 and Scout wheat cultivars were coated with rhizobacteria (176 isolates) and germinated in nonautoclaved or autoclaved field soils in the greenhouse. The dry weights of cereals seedlings (3 wk old) were not significantly affected by bacterial treatments in the autoclaved soils regardless of plant species. Eight cereal Pseudomonas rhizobacteria increased seedling growth significantly in one or more of corn, sorghum or wheat cultivars in nonautoclaved soils in the greenhouse. The stand density, stalk and root rot incidence and grain yield of two corn hybrids were not improved by coating their seeds with growth-promoting rhizobacteria during 2 yr of field testing. Some isolates actually reduced the stand and grain yield of certain corn hybrids in the field. The effect of each rhizobacterium varied considerably between plant species and between cultivars within the same species. The growth-promoting rhizobacteria differed significantly in their ability to inhibit growth of 14 plant pathogenic bacteria and fungi on agar media.Key words: Biological control, antagonism, Pseudomonas, corn, sorghum, wheat, stalk rot