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‘Tifguard’ (Reg. No. CV‐101, PI 651853) is a runner‐type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) cultivar released by the USDA‐ARS and the Georgia Agricultural Experiment Stations in 2007. Tifguard was developed at the University of Georgia Coastal Plain Experiment Station, Tifton, GA. Peanut cultivars are available that have high resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] or spotted wilt caused by tomato spotted wilt tospovirus (TSWV). However, no cultivars exist that have resistance to both pathogens. Our research objective was to combine resistance to both pathogens in a single cultivar. Breeding populations were developed by hybridizing the TSWV‐resistant ‘C‐99R’ with the nematode‐resistant ‘COAN’. Selection for nematode resistance was conducted using standard greenhouse screening techniques. Selection for TSWV resistance was conducted in the field with natural virus infection. A breeding line (C724‐19‐15) was selected that had high resistance to both pathogens. Tifguard exhibited higher resistance to TSWV and higher yield than standard check cultivars when grown in fields with little or no nematode pressure. Because of its high level of resistance to both TSWV and M. arenaria, Tifguard had significantly higher yield than all others entries when grown in two locations with high pressure from both pathogens. This cultivar should be valuable for peanut growers who have to deal with both pathogens.

Peanuts (Arachis hypogaea L.) are often subjected to drought during some period in the growing season. A large root system may improve the plant's ability to continue growth during a drought. During greenhouse and field screening trials for resistance to the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood, race 1],16 peanut genotypes were observed to have very large root systems. Using these 16 genotypes plus cultivars Florunner, Southern Runner, and germplasm line Tifton 8 as checks, several studies were conducted to evaluatethese genotypesfordrought avoidance characteristics. In the first study, root and shoot development were observed at 15-d intervals on plants grown from seed in sand-filled pots. In a second 2-yr study, selections were grown in the field under portable rain-exclusionshelters that created controlled periods of stress. In addition, the genotypes were also planted and observed in unsheltered naturally drought stressed field plots. In the sand-filled pot study, plant inventory (PI) numbers 315628, 268885, 318740, 269106, and 314893 developed the largest root systems. In the field drought stress studies, lowvisualstress ratings were recorded for Southern Runner, Tifton 8, PI 295722, and PI 315628. Low canopy temperatures characterized PI 315628, Tifton 8, and PIs 295722,259637, and 268885. When averaged over three tests, sheltered (1991and 1992)and unsheltered (1991), Tifton 8, PI 318740, Florunner, PI 315622, and PI 315628 produced the highest yields. Two of these higher yielding genotypes (Tifton 8 and PI 315628) had low stress and temperature ratings and PI 315628also had the largest root system measured in this study.'Cooperative investigation between the Univ. of Georgia, College of Agric. and Environ. Sci. and USDNARS. Mention of a product name given for information and should not be considered an endorsement to the exclusion of like products.

Peanuts become contaminated with aflatoxins when subjected to prolonged periods of heat and drought stress. The effect of drought tolerance on aflatoxin contamination is not known. The objectives of this research were to evaluate preharvest aflatoxin contami nation in peanut genotypes known to have drought tolerance and to determine the correlation of drought tolerance characteristics with aflatoxin contamination. Twenty genotypes with different levels of drought toler ance were grown in Yuma, AZ«(a desert environment) and under rain-protected shelters in Tifton, GA. Two drought-tolerant genotypes (PI 145681 and Tifton 8) and an intolerant genotype (PI 196754) were selected for further examination in a second experiment with two planting dates in 1997 at Tifton. Drought and heat stress conditions were imposed for the 40 d preceding harvest. The drought-intolerant genotype had greater preharvest aflatoxin contamination than Florunner (the check cultivar) in the tests conducted in 1997. Both droughttolerant genotypes had less preharvest aflatoxin con tamination than Florunner in these tests. Significant positive correlations were observed between aflatoxin contamination and leaf temperature and between afla toxin contamination and visual stress ratings. Leaf tem perature and visual stress ratings are less variable and less expensive to measure than aflatoxin contamination. Leaf temperature and visual stress ratings maybe useful in indirectly selecting for reduced aflatoxin contamina tion in breeding populations.

Drought stress has been heavily investigated for its effects on production efficiency and yield, but less attention has been given to its effects on peanut quality. Peanuts (Florunner cv) were stressed for 30 days, by withholding irrigation and using shelters, at the preflowering period (stressl), pod formation period (stress2), and maturation period (stress3). Fatty acid composition, oleic linoleic ratio (OIL), computed iodine value (IV) and tocopherol content of Florunner peanuts were investigated. The fatty acid composition acid composition, OIL ration, IV, alpha-tocopherol (a-T) and gamma-tocopherol (y-T) were significantly affected by drought stress and peanut grade. As peanuts increased in size regardless of stressing period, long chain saturated fatty acids [arachidic acid (20:0), behenic acid (22:0), and lignoceric acid (24:0)], eicosenoic acid (20:1), (OIL), and a-tocopherol decreased significantly. Stressing peanuts during the maturation period is most detrimental to peanut stability, decreasing OIL ratio and increasing IV.Key Words: Arachis hypogaea L., peanut grade, drought stress, fatty acids, OIL ratio, IV, tocopherol Drought conditions cause low yields and poor grade peanuts (4,21), decrease subsequent germination (15), and increase incidence of aflatoxin contamination (5). The Arachis hypogaea L. cv. Florunner is more sensitive to drought at the seed filling phase compared to the podinitiation phase (16), while cv. Valencia is most sensitive at the late flowering and pod formation period (17). Stressing cv Robut33-1 during the pre-flowering phase increases the yield 13-19% (12). Late-season drought is more detrimental to final pod yield than early-season stress (22). Mid-season drought (65-100 days after planting) decreases the yield and increases the portion of immature pods (13).A peanut seed contains approximately 50% of its weight as oil. Generally the oleic and linoleic acid proportions together make up 80% of the fatty acid in peanut oil (1). Several factors affect the quantity of the individual fatty acids in peanut oil, including variety, seasonal variation, the part of the seed analyzed, abnormalities such as disease and insect damage (3), genotype (14), production location and! or temperature condition under which the crop is grown (18), maturity (19,26), and the market grade (11). Peanut storage qualities and nutritional quality are both dependent on the relative proportions of the saturated and unsaturated fatty acids that make up the oil. From a nutritional standpoint, a high polyunsaturated fatty acid content is desirable in lowering plasma cholesterol level and low-density lipoprotein, which may reduce the risk ofcoronary heart disease and atherogenesis (8). Fats containing high percent oleic acid also may be beneficial in lowering blood cholesterol 21 level (7). The total amount of unsaturation is inversely proportional to the keeping quality of the oil, oxidative rancidity increases with increased level of the polyunsaturated fatty acids which cause associate odors and ...