Identification of quantitative trait loci for resistance against soybean sudden death syndrome caused by Fusarium tucumaniae

The objective of this work was to identify genomic regions that underlie resistance to Fusarium tucumaniae sp. nov., the causing agent of sudden death syndrome (SDS) in soybean in South America, using a population with a genetic background different from that previously reported for Fusarium virguliforme sp. nov. (F. solani f. sp. glycines), also responsible for SDS in soybean. Although major genes and quantitative trait loci (QTL) for SDS resistance have been identified, little is known about the same disease caused by Fusarium tucumaniae sp. nov., in South America. To identify genetic factors related to resistance to F. tucumaniae and DNA markers associated with them, a QTL analysis was performed using recombinant inbred lines. The map locations of the four loci, here identified, differed from those SDS resistance QTL previously described. It was screened a residual heterozygous line (RHL), which was heterozygous around the most effective QTL, RSDS1, and homozygous for the other genomic regions. The genetic effect of RSDS1 was confirmed using near-isogenic lines (NIL) derived from the RHL. The line which was homozygous for the Misuzudaizu genotype showed resistance levels comparable with that of the line homozygous for the Moshidou Gong 503 genotype

Registration of DT99-16864 Soybean Germplasm Line with Moderate Resistance to Charcoal Rot [\u3cem\u3eMacrophomina phaseolina\u3c/em\u3e (Tassi) Goid.]

Charcoal rot, caused by Macrophomina phaseolina (Tassi) Goid., is a disease that is a worldwide problem in soybean [Glycine max (L.) Merr.] production for which no highly resistant cultivars are currently available. It has been estimated that charcoal rot was among the most important diseases for suppressing yield of soybean in the USA from 1996 to 2007. Soybean breeding line DT99-16864 (Reg. No. GP-404, PI 675996), with moderate resistance to charcoal rot disease, was developed and released by the USDA-ARS, Stoneville, MS. DT99-16864 originated from a single F5 plant derived from a cross of ‘S59-60’ × ‘Bolivar’. The breeding population was advanced from the F2 to the F5 generation using the single-seed descent method. Colony-forming units, root and stem severity scores, and other rating methods indicated that DT99-16864 had significantly lower levels of M. phaseolina infection than susceptible checks in trials in Stoneville, MS, and Jackson, TN. In the Uniform Soybean Tests–Southern States, DT99-16864 was not significantly different from the check cultivars ’5002T’ and ’5601T’ for yield. DT99-16864 belongs to maturity group V and is later in maturity than DT97-4290, a moderately resistant charcoal rot line that is adapted to the midsouthern United States. The well-documented moderate resistance of DT99-16864 to M. phaseolina infestation, and good yield potential, will make this line useful for research and breeding