Soybean (Glycine max (L.) Merr.) winter nurseries have been planted in Puerto Rico at the USDA's Isabela farm for 25 consecutive years. The field has had one soybean crop each year, with a summer fallow period between winter nursery seasons. In February 1998, during an inspection of root nodulation, cysts were discovered on roots of an F2 population (Benning × Pureunkong). Microscopic examination of roots confirmed the presence of female nematodes of Heterodera glycines Ichinohe in various stages of development. No cysts were found when soil and roots were randomly sampled at various growth stages (R1 to R7) from other soybean fields in Puerto Rico (Isabela, Salinas, Lajas, and Juana Diaz). Also, no cysts were observed on roots of common bean (Phaseolus vulgaris) at growth stages R7 to R8 in a neighboring research field. However, cysts were observed on 35-day-old roots of soybean cv. Lee, common bean, and pigeon pea (Cajanas cajun) grown in the above infested soil. A race assay, slightly modified from standard protocols (3), determined that the infested soil contained race 2 of H. glycines. The infested field was rotated to sorghum during the summer of 1998 and then soybeans were planted in the 1998-1999 winter nursery. H. glycines occurs in at least 26 states of the U.S., and in Canada, Asia, and South America (1,2). References: (1) M. L. Mendes and D. W. Dickson. Plant Dis. 77:499, 1993. (2) R. D. Riggs and D. P. Schmitt. 1989. Soybean Cyst Nematode. Page 65 in: Compendium of Soybean Diseases. 3rd ed. J. B. Sinclair and P. A. Backman, eds. American Phytopathological Society, St. Paul, MN. (3) D. P. Schmitt and G. Shannon. Crop Sci. 32:275, 1992.
Effect of Aspergillus niger NBC001 on the soybean rhizosphere microbial community in a soybean cyst nematode-infested field
