Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/1996
Publication Date: N/A
Interpretive Summary: Brown spot of soybeans, caused by the fungus Septoria glycines, is the most prevalent foliar disease of soybeans in Illinois and it causes significant yield losses. Immunity or single gene resistance in soybeans to S. glycines has not been reported. Resistance to brown spot has not been found by conventional screening methods, so in vitro selections using fungal pathotoxins has been used to develop disease-resistant plants. In this study, the regenerated lines (R3 to R7 generations) were evaluated for brown spot resistance. In addition, selections from the R5 and R6 generations were evaluated for yield and brown spot resistance. Plants were classified as intermediate and susceptible among the R3 to R7 generations in 1992, 1993, and in 1994. Four of 348 lines had a stable intermediate reaction with significantly lower disease severity than that of parental cv. BSR201. Three regenerated lines, 2728, 2733, and 2734, had significantly less disease and higher yields than that of parental cv. BSR201. This study shows that selections made for disease resistance and higher yields were effective and these findings will be used by researchers interested in improving soybean resistance to brown spot.
Technical Abstract: Regenerated soybean lines from the R3 to R7 generations were field evaluated for resistance to Septoria glycines from 1991 to 1994. The regenerated lines from cvs. BSR201, Fayette, and L86P-1615 were selected from calli resistance to a pathotoxin produced by S. glycines. Selected resistant plants from the R3 generation produced R4 progeny that were both susceptible and resistant in 1991. Brown spot resistance was intermediate and susceptible among the R3 to R7 generations in 1992, 1993, and in 1994. Of the 2,513 regenerated plants, 1 to 31% had an intermediate reaction to S. glycines from the R3 to R7 generations. Four of 348 lines with an intermediate reaction in the R5, F4, and F5 generations had a stable intermediate reaction with significantly (P = 0.05) lower disease severity at growth stage R5 than that of parental cv. BSR201. Ten and nine lines from calli of cv. BSR201 with an intermediate and susceptible reaction, respectively, to S. glycines in 1992 from either R5 or R6 generations and five commercial cultivars were evaluated for brown spot resistance, the number of days to maturity, and yield in 1993 and 1994. Area-under-disease-progress-curve (AUDPC), days to maturity, and yield varied among entries. The 10 lines selected with an intermediate reaction had lower AUDPC, matured later, and had higher yields than the nine susceptible lines. Three regenerated lines, 2728, 2733, and 2734, had significantly (P = 0.05) lower AUDPC, later maturity, and higher yields.