Heterodera glycines Ichinohe is a serious pest of soybean [Glycine max (L.) Merr.] in the USA. Several Races of H. glycines occur in the soybean growing areas. Soybean accessions with resistance to Races 3, 5, and 14 have been identified. Data on reaction of these accessions for Races 1 and 2 are not available. Our objective was to bioassay these accessions for resistance to H. glycines Races 1 and 2. Eighty‐six accessions, host differentials, and susceptible control were bioassayed during 1995 to 1996 for each of the two Races in thermoregulated water baths in the greenhouse. The results indicated that 52 accessions had resistance to H. glycines Race 1, and 24 accessions had resistance to Race 2, respectively. Soybean PIs 89772, 90763, 404166, 404198A, 437654, 437690, 438489B, 567491A, and 567516C were either resistant or moderately resistant to both Races. These are potential resistance sources to H. glycines Races 1, and 2 for developing resistant soybean cultivars. These PI lines are being fingerprinted by means of molecular markers to identify the unique lines to allow broadening the diversity of resistance gene utilization.

No abstract

No abstract

The tactic of choice for managing soybean cyst nematode (SCN) in infested fields is the use of resistant cultivars. Because expression of SCN resistance is dependent on the occurrence and frequencies of genes for virulence in SCN populations, labeling of SCN-resistant cultivars can be difficult and, occasionally, highly misleading, leading to unanticipated yield losses. The authors' objective was to offer a set of standards for assessing and labeling SCN-resistant cultivars that would allow farmers to make direct comparisons of cultivars. Accepted for publication 15 March 2009. Published 13 May 2009.

No abstract

No abstract

Isolines for maturity within a common background may be useful in research that attempts to determine the effect of maturity group adaptation on soybean [Glycine max (L.) Merr.] growth or yield. Although the effects of maturity genes on soybean phenology have been studied extensively, little is known about their effects on other soybean characteristics. Field experiments were conducted near Columbia, MO, in 1991 and 1992 to determine the effects of three major maturity genes on growth and development of soybean. Four near‐isogenic strains (isolines) were replicated four times in a completely randomized design: L71‐920 (e1e2e3), Clark (e1E2E3), L74‐441 (E1E2e3), and L67‐1474 (E1E2E3). Vegetative and reproductive characteristics were recorded for five plants within each plot. Late‐maturing isolines were taller and had more leaves than early‐maturing isolines, but stem growth and leaf initiation rates were similar. Late‐maturing isolines produced more flowers and pods because they had more nodes than early‐maturing isolines. Late‐maturing isolines produced more than 25% of total yield on branches, whereas early‐maturing isolines produced approximately 10% of total yield on branches. Because the isolines used in this study had consistent differences for plant phenology, they can be useful components of experiments that include maturity as a factor. However, changes in phenology also changed plant morphology.

No abstract