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.
To assess maturity distributions of shelled-stock peanut lots, a method was developed to characterize peanut kernels into one of three possible maturity classes based on testa texture and color and kernel shape. Kernels having testa with longitudinal wrinkles, a raisin-like texture, light color and slightly elongated shape were classed Immature and predominately were shelled from pods in the Hull-Scrape categories White, Yellow I, and early-Yellow 11. Kernels with a smooth testa, pink to dark pink and with a more rounded appearance were classed Mid-mature and predominately were shelled from pods in the late-Yellow 11, Orange, and early-Brown Hull-Scrape classes. Kernels with awaffle-like surface texture, dark pink to brown testa, and a more rounded appearance were classed as Mature, and predominately were shelled from pods in the midand late-Brown and the Black Hull-Scrape categories. Attempts to automate the system using color alone were unsuccessful; to be a reliable maturity sorting technique, both testa texture and color pattern had to be considered.Equipment brands and manufacturers are given as information for the reader and are not an endorsement to the exclusion of other products which may perform the same function. (1987) reported that maturity and size of kernels within a cultivar are related. Therefore, the current size related market classes of shelled stock peanut (Jumbo, Medium, No. 1) reflect a degree of maturity. However, kernel size and maturity are not perfectly correlated (Sanders, 1989). Varying environmental conditions can result in smdl mature kernels or large immature kernels.Tollner and Hung (1993) used NMR readings for moist and dried peanuts to assess peanut maturity. In 1887, Whitaker et at. found that Near Infared Redlectance ( N I H) could be used to measure kernel maturity.Past research has determined that 'shriveled' o r 'writiklcd' testa are indicators of immaturity ( Parham, 1942;Mixon, 1963;Aristizabal et at., 1969). Pickett (l9SO) noted that a reliable and simple method of determining niutiirity of' developing peanut kernels included a coin hination of wed texture and testa color. Schenk (1961) also used k t w d surface texture (wrinkled, smooth) and testti color (wlritc to pink to red with brown splotches) tu clescritw the stwl maturing process. Pattee et al.(1 970 and refined in 1974) gave a detailed description of charitctcvistices itssociilted
Peanut maturity and several peanut quality factors are closely related. An examination of peanut physical properties revealed that by sorting farmer-stock peanuts into pod density classes before shelling, the maturity distributions within shelled-stock classes can be manipulated. An unsorted sample of farmer-stock peanut having an initial maturity distribution in No. 1 kernels of 66% immature, 23% mid-mature and 11% mature was sorted using a gravity separator into four pod-density fractions ranging from 98% immature and 2% mid-mature in the least dense fraction to 8% immature, 43% mid-mature and 49% mature in the most dense fraction. Along with improvements in maturity distributions, we also found that the higher test weight fractions (higher pod density) had less ailatoxin and a greaterpercentage oflarge kernels than did the low testweight fractions. Many density sorting devices were tested, including air columns, pod cleaners, and gravity tables. All of these devices were capable of sorting pods into maturity groups, but the gravity table was the most precise.
Olive production in the southeastern United States has recently begun to increase from demand for locally produced virgin olive oil. With no established commercial production as a reference, information about the effects of indaziflam residual herbicide on newly established trees was evaluated over time for up to 3 yr on loamy sand soils. Multiple spring and autumn applications of indaziflam at different rates were applied to the same newly planted or 1-yr-old olive trees in different experiments in consecutive years. Visual injury, height, and caliper diameter measures were taken monthly during the growing season up to six times. Regression analysis of treatments over time indicated no differences in olive tree growth for plots treated with indaziflam at 38, 75, or 150 g ai ha–1 up to five times in 3 yr, compared with nontreated controls. This information will be beneficial as olive growers seek viable weed control options when establishing new groves in the region.
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