Plant-growth-promoting rhizobacteria and kinetin as ways to promote corn growth and yield in a short-growing-season area

The base temperature for germination of corn is approximately 10 degrees C, which results in slow germination and emergence of corn crops sown into co ol soils. The effects of plant-growth-promoting rhizobacteria (PGPR) and ki netin on grain and sweet corn emergence, plant growth and yield were studie d under short season conditions in 1996 and 1997. Two PGPR strains (Serrati a proteamaculans 1-102 and Serratia liquefaciens 2-68) were used. The kinet in concentrations were 0, I and 5 mu M. The experiment was structured as a randomized complete block design with four replicates. The plant growth res ponses were variable and depended on the PGPR strain, harvest date and grow th parameters evaluated. There were interactions among PGPR, kinetin and co rn hybrid. PGPR provided a greater stimulation of seedling emergence than k inetin. PGPR strain 1-102 was best at promoting emergence. One month after planting, both PGPR and kinetin increased plant growth, and PGPR strain 2-6 8 resulted in a greater growth than that of strain 1-102. PGPR strain 2-68 plus 1 mu M kinetin was the best treatment for promoting plant growth. The plant height and root dry weight of sweet corn were less affected than thos e of grain corn. The effects of PGPR on plant growth decreased as the plant s developed. Two months after planting, there were no effects of kinetin on plant growth, however, PGPR still had positive effects on the leaf area of grain corn, but they decreased the leaf area of sweet corn. The plant dry weight of grain corn was increased by PGPR strain 2-68. The grain corn yiel d was increased by PGPR strain 2-68 in both years. In 1997, PGPR strain 2-6 8 increased the sweet corn yield. Kinetin alone had no effects on yields in either year for the two cultivars studied. (C) 1999 Elsevier Science B.V. All rights reserved.