Location: Market Quality and Handling Research
Title: Maturity Effects on Contamination of High-Oleic Peanut Lots with Normal-Oleic Seeds of a Large Seeded Virginia Type Peanut Variety. Authors
Submitted to: American Peanut Research and Education Society Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 7, 2014
Publication Date: N/A
Interpretive Summary: The peanut industry has the need to keep lots of high-and normal-oleic peanuts separated. Due to the fact that peanuts on the plants are maturing at different times even at harvest dates, mixed lots are found. The changes in fatty acid profile were tracked over the course of pod development for a large seeded virginia type and a normal-oleic virginia type and compared to a normal-oleic runner type and its high-oleic sister line. All samples showed a wide range of maturities throughout the study. At harvest it was possible to remove most of the low oleic, immature seeds from the high oleic runner sample by conventional pod sizing. The very large seeded virginia type continued to have mixed high and normal-oleic seed even in the very largest pods showing the conventional sizing was not able to produce a pure high-oleic peanut lot at final harvest.
Technical Abstract: The need to segregate high- and normal-oleic peanut seeds has lead to investigations into potential sources of mixing. Previous work in our lab examined the development of in two lines of virginia type seeds, Bailey (normal-oleic) and Spain (high-oleic) for changes in the oleic to linoleic ratios (O/L) due to the indeterminate nature of peanut flowering. An additional study was conducted with runner types seeds from two sister lines, Tifguard (normal-oleic) and 68-17 (high-oleic). Changes in the fatty acid profiles (FAP) and pod and seed moisture content were determined from representative plants from the period of initial pod development at 62 days after planting (DAP) until harvest at 148 DAP. At each sampling, all seeds were removed from 5 plants, pods and seeds (>0.1g) were weighed, and moisture content and FAP determined. At final harvest, a separate 4500 kg sample was maturity sorted by pod color prior to seed sizing and single seed FAP analyzed. Although growth patterns were similar in that each time sampling produced a range of pod sizes, the largest range was found in the high-oleic virginia seed. It was found that the FAP of an individual peanut seed was highly correlated with seed size, but not pod size or pod maturity. Pods can be of marketable size but still be developing small seeds with low O/L at the end of the growing season on high-oleic plants of both market types, but this was more evident in the virginia type. The range of seed sizes was smaller and more consistent across maturities for the runner sister lines and for Bailey. At maturity, there was still a range of seed sizes and maturation stages for both market types, but moisture content was higher in the more immature and usually smaller seeds. When sorting by pod color, the most mature seeds had the highest O/L ratios in the high-oleic lines of both market types. Sizing seeds could reduce the number of low O/L seeds found in Spain, a very large seeded virginia type, but this would not be as effective with the runner type. Without some type of sorting mechanism that can detect lipid character, it will be impossible to guarantee lots will be 100 % segregated regardless of handling strategies. A preliminary, small scale genotypic evaluation of the two virginia lines showed that not all the Spain seed were homozygous for both mutant alleles responsible for the high-oleic genotype and were normal-oleic even at maturity. Thus, impure or segregating lines, as well as normal high-oleic development may lead to low O/L contamination in high O/L lots.