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Increasing the ratio of oleic to linoleic acid (O/L) in peanut (Arachis hypogaea L.) significantly improves the nutritional and quality attributes of the crop. In currently grown cultivars, the O/L ratio ranges from 0.8 to 2.5. Variation in peanut for O/L ratio has been characterized, and the O/L ratio is digenically inherited at two loci designated as Ol1 and Ol2 Previous research has been conducted with Virginia‐ and runner‐type peanut; however, there have been no reports regarding the inheritance and allele frequency at these loci in Spanish‐type peanut. The objectives of this study were to determine if the inheritance of the high oleate trait in Spanish‐type peanut is similar to that previously reported and to determine the allelic composition of Spanish‐type peanut at Ol1 and Ol2 Six different Spanish‐type peanut cultivars (low oleate) were hybridized with F435‐2—2 (high oleate). F2 and BC1F1 progenies were evaluated for the O/L ratio. Segregation patterns indicated that high oleic acid content is digenically inherited in Spanish‐type peanut, but there seems to be more allelic variation both within and among these cultivars. In addition, variation within the high and low oleate ratio classes indicated that other factors may be involved in determining the precise O/L ratio.

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Field screening tests were conducted in 1991, 1992, and 1993 to identify Sclerotinia blight-resistant runner-type peanuts. Selections were made from three 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 cultivar Tamspan 90 and TxAG-5 germplasm. Families within populations were planted as single row 3 × 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 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 ≥80% infection in the plot. Correlation between area under disease progress curve values of both methods was high (>.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 (α = .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.