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Effect of Rhizobacteria and Metham-Sodium on Growth and Root Microflora of Celery Cultivars. J. O. Becker, Department of Nematology, University of California, Riverside 92521; C. A. Hepfer(2), G. Y. Yuen(3), S. D. Van Gundy(4), M. N. Schroth(5), J. G. Hancock(6), A. R. Weinhold(7), and T. Bowman(8). (2)(3)(5)(6)(7)(8)Department of Plant Pathology, University of California, Berkeley 94720; (4)Department of Nematology, University of California, Riverside 92521. Phytopathology 80:206-211. Accepted for publication 1 August 1989. Copyright 1990 The American Phytopathological Society.. DOI: 10.1094/Phyto-80-206.

Treatment of celery transplants with several rhizobacterial strains or fumigation of soil with metham-sodium promoted early plant growth and increased yield in fields infested with Fusarium oxysporum f. sp. apii. Results of both bacterial and chemical treatments varied substantially among planting times and in successive years. Other factors affecting results were the cultivar and bacterial strains that were tested. Pseudomonas aureofaciens strain PGS 12 caused significant increases in early plant growth in three of three trials and in yield in two of three trials with cultivar Fordhook. Increases in early plant growth or yield, however, were not obtained when cultivars Tall Utah 52-70 HK (four trials) and Tall Utah 52-70 R (two trials) were treated with PGS 12. One of the trials contained all three cultivars in a factorial design. Bacillus sp. X2.2 caused increases in early plant growth and yield with cultivar Fordhook in one trial and had a significant interaction with all three cultivars in the combined trial. Fumigation with metham-sodium resulted in harvest weight increases varying from 18 to 75% with the cultivar Fordhook in different seasons, and from 18 to 81% among cultivars planted at the same time. Early-season plant growth promotion did not necessarily correlate with shoot weight of plants at harvest. Some qualitative and quantitative differences in fungal microflora on roots were observed in the different bacterial and chemical treatments, but, in general, the detection methods for evaluating the seasonal succession of microflora under field conditions were too insensitive and labor-intensive to conclusively relate plant growth promotion to the presence or absence of specific microorganisms, including F. o. apii.

Additional keywords: bacterization, biological control, PGPR.