Genotype evaluations for productivity and quality of peanut in West Texas

Peanut (Arachis hypogaea L.) acreage has rapidly increased on the Texas Southern High Plains. In 1995, there were only 17,806 hectares planted, however, in 1998, 76,893 hectares were planted. Yields have been greater than both state and national levels, averaging 3700 kg/ha. The production area is characterized as semi-arid, with rainfall averaging 450 mm per year. The relatively high elevation (approx. 900 m) and cool night temperatures result in a shorter growing season, a lack of adequate heat unit accumulation, and delayed maturity of the peanut crop. This research was designed to evaluate a wide range of genetic types for variation in yield, maturity, and oil quality under West Texas environmental conditions. The genetic material (consisting of 35 entries, including experimental and commercial lines) was grown in Terry County, Texas, southwest of Lubbock, Texas, In 1998, 1999, and 2000. In 1998, center pivot Irrigation was used while in 1999 and 2000, subsurface drip tape was used to provide irrigation. In all three years, irrigation was adequate to provide 6 mm per day, on a five-day frequency. Plots were 2 rows wide by 6 m long with 3 replications in 1998, and 2 rows wide by 13 m long with 4 replications In 1999 and 2000, with row spacing of 0.80 m all years. In 1998 and 1999, maturity was estimated using the Hull Scrape Method beginning at 85% of the "long-term average" (LTA) heat unit accumulation and continued at 5% intervals until 100% of the LTA heat unit accumulation had been reached. Yield was determined by harvesting the two rows with a commercial digger and threshing with a stationary small plot thresher. Oil was extracted from a sample of each plot to determine oil content. Fatty acids were methylated to form fatty acid methyl esters, which were then analyzed by gas chromatography. Oleic acid/linoleic acid ratios were calculated, along with unsaturated/saturated fatty acid ratios. Genotypic variation was present in yield, maturity, grades, oil content, U/S ratios, and 0/L ratios (P < 0.05). Large differences in yield were noted among genotypes and between years. 0/L ratios were considerably lower than those previously reported in other peanut production areas. Mean yields were plotted against mean grades (used as maturity indices) and divided into four quartiles. Thirteen entries fell into the quartile labeled as "high yield and early maturity." Four entries were high oleic genotypes with high yield and early maturity.