Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 1995
Publication Date: N/A
Interpretive Summary: Outbreaks of sclerotinia blight disease, caused by the fungus Sclerotinia minor, in peanut in Oklahoma, Texas, Virginia, and North Carolina result in significant yield losses. Management of sclerotinia blight by chemicals is expensive, and often does not provide acceptable control. Therefore, the objective of this research was to identify sclerotinia-resistant sources in nthe peanut germplasm. This paper discusses the results of a 3-year study i which the sclerotinia blight reaction of several peanut lines, from the breeding program at Texas A&M University, in field plots was determined. Several peanut lines were identified as resistant to the sclerotinia pathogen. A selection of one of these lines (PI 798736) was released in 1990 by Texas A&M and the Agricultural Research Service as a sclerotinia- resistant peanut cultivar 'Tamspan 90'.
Field screening tests were conducted in 1991, 1992, and 1993 to identify Sclerotinia blight-resistant runner-type peanuts. Selections were made from 3 populations, "backcross to runner", "backcross to Tamspan 90", and "single-cross." Runner parents were chosen for agronomic qualities and resistance to other pathogens. Resistant (spanish) parents used were 'Tamspan 90' cultivar and TxAG-5 germplasm. Families within populations were planted as single-row 3 m x 0.9 m plots. Repeated plant-by-plant inspections (PBPI) were made for assessment of sequence of infection and subsequent calculation of an area under the disease progress curve (AUDPC). Most families in the backcross to Tamspan 90 population consistently had a disease reaction close to or lower than Tamspan 90, the resistant parent, but also retained undesirable plant forms (i.e., upright). By 1993, the F2:5 backcross to runner population had the highest percentage of runner type families (88%) and a mean disease reaction close to Tamspan 90. Whole plot evaluation of Sclerotinia blight severity was compared with PBPI for effectiveness on a segregating population containing a total of 298 F4:7 single-cross and F2:5 backcross entries. The whole-plot system used a scale of 0 = no visible plot infection to 5 > or equal to 80% infection in plot. Correlation between AUDPC values of both methods was high (>0.85). Remnant seed of selections screened for resistance in the greenhouse were planted in the field and evaluated for resistance. Chi-square test for independence indicated a significant (alpha = 0.012) relationship between greenhouse and field performance. Field screening and limited greenhouse screening appears to be an effective way to develop resistant runner-type peanut lines.