D. W. Gorbet

Storage water activity affects flavor fade in high and normal oleic peanuts

Abstract Studies were conducted on roasted high oleic (HOP) and normal oleic peanuts (NOP) to investigate the effect of storage water activity on flavor changes. Peanuts were stored for 0–7 weeks at 0.19 and 0.60 water activities ( a w ). Volatile flavor compounds were analyzed using solid phase microextraction–gas chromatography. HOP had better oxidative stability compared to NOP, which had peroxide values 7–10 times higher. Sensory evaluation showed HOP retained roasted peanutty characteristics and resisted off-flavor development during storage better than NOP. Pyrazines remained at higher levels after storage in HOP, which also formed lower levels of aldehydes. Oxidation and sensory changes were higher at low a w .

Field Response of New Peanut Cultivar UF 91108 to Tomato Spotted Wilt Virus

Epidemics of spotted wilt, caused by tomato spotted wilt tospovirus (TSWV), were monitored in field plots of the new runner-type peanut (Arachis hypogaea) cv. UF 91108, in advanced breeding line F 84 × 9B-4-2-1-1-2-b2-B, in runner-type peanut cvs. Southern Runner and Florunner, and in Virginia-type cv. NC-V11 at two locations in 1994 and 1995. Epidemics of spotted wilt were suppressed in UF 91108 compared to the standard runner-type cv. Florunner. Final disease incidence, standardized area under the disease progress curve values, and final disease intensity ratings were lower in UF 91108 than in Florunner and were similar to those in the moderately resistant cv. Southern Runner. Results indicate that new cv. UF 91108 represents a new potential tool for management of spotted wilt in peanut production areas of the southeastern United States. UF 91108 is the first peanut cultivar in which an oil composition of approximately 65% oleic acid is combined with a moderate level of field resistance to TSWV. Epidemics of spotted wilt also were suppressed in breeding line F 84 × 9B-4-2-1-1-2-b2-B. Across the four tests, the effects of NC-V11 on epidemic development, final incidence, and spotted wilt intensity ratings were not consistent relative to the other genotypes. Use of final disease intensity ratings provided separation of the genotypes similar to use of final incidence of spotted wilt. Assessment values by these two methods were highly correlated. In three of four experiments, final disease intensity ratings were more closely correlated with pod yield than was final incidence. The new intensity rating method described in this paper requires much less time and effort than determining disease incidence and may be a practical alternative to individual plant assessment for characterization of genotype responses to TSWV.

Disease progress of tomato spotted wilt virus in selected peanut cultivars and advanced breeding lines

Epidemics of spotted wilt, caused by tomato spotted wilt tospovirus, were monitored in field plots of advanced breeding lines of peanut (Arachis hypogaea) GA T-2846, F 84X9B-1-1-1-b3-B, and F 84X1A-7-2-1-1-b2-B, and in runner-type peanut cultivars Georgia Browne, Southern Runner, and Florunner in one location in 1993 and in three locations in 1994. Across all tests, final incidence of spotted wilt and standardized areas under the disease progress curves were lower in the three breeding lines, Georgia Browne, and Southern Runner compared to standard runner-type cultivar Florunner. With some exceptions, numbers of tobacco thrips (Frankliniella fusca), western flower thrips (F. occidentalis), and larvae of Frankliniella spp. were similar for all peanut cultivars and breeding lines. There was no evidence that differences in disease progress among the six entries were due to differences in preference by thrips or to suitability for thrips reproduction. Results indicate that all three advanced breeding lines evaluated in this study represent potential tools for management of spotted wilt in peanut production areas of the southeastern United States.

Response of New Field-Resistant Peanut Cultivars to Twin-Row Pattern or In-Furrow Applications of Phorate for Management of Spotted Wilt

Field experiments were conducted at Marianna, FL in 2006 and Tifton, GA in 2006 and 2007 to compare new peanut (Arachis hypogaea) cultivars to the moderately resistant cv. Georgia Green and the highly resistant cv. AP-3 for field resistance to Tomato spotted wilt virus (TSWV), genus Tospovirus, and to determine the effects of in-furrow application of phorate insecticide and use of twin-row versus single-row patterns on incidence of spotted wilt in these cultivars. Cvs. Georgia Green, AP-3, Georgia-03L, Georgia-01R, Florida-07, McCloud, and York were evaluated in all five experiments, and Tifguard was added in experiments at Tifton. All cultivars except McCloud had lower incidence of spotted wilt than Georgia Green in all experiments. McCloud was intermediate in resistance to TSWV and had lower incidence of spotted wilt than Georgia Green in four of five experiments. Use of the twin-row pattern also reduced incidence of spotted wilt in McCloud in both years. On Georgia Green, phorate reduced incidence of spotted wilt in 2007 and twin-row pattern reduced incidence in both years. Phorate had no effect on spotted wilt in AP-3, Georgia-03L, McCloud, Georgia-01R, or Tifguard in either year. Twin-row pattern reduced either final incidence or area under the disease progress curve in all cultivars in at least 1 year of the study. All of these new cultivars should reduce the risk of losses to spotted wilt compared with Georgia Green. In highly resistant cultivars, especially AP-3, York, and Tifguard, use of phorate insecticide or twin-row pattern may not be necessary, and may not provide noticeable benefit in reduction of spotted wilt or increased yield.

Field Evaluation of Tomato spotted wilt virus Resistance in Transgenic Peanut (Arachis hypogaea)

Spotted wilt, caused by Tomato spotted wilt virus (TSWV), is a devastating disease of many crops including peanut (Arachis hypogaea). Because the virus has a broad host range and is spread by ubiquitous thrips, disease management by traditional means is difficult. Developing new peanut cultivars with resistance to TSWV presents a significant challenge since existing genetic resistance in peanut germ plasm is limited. A genetic engineering approach appears to have great potential for resistance enhancement to TSWV. Transgenic peanut progenies that expressed the nucleocapsid protein of TSWV were subjected to natural infection of the virus under field conditions during the growing seasons of 1999 and 2000 in Tifton, GA, and in three locations (Tifton, GA, Marianna, FL, and Headland, AL) in 2001. Significantly lower incidence of spotted wilt was observed for the transgenic progeny in comparison to the nontransgenic checks in the field (in multiple years and locations) as well as during challenge inoculation under controlled environmental conditions. This transgenic event could potentially be used in a traditional breeding program to enhance host resistance.

Differential Response of Selected Peanut (Arachis hypogaea) Genotypes to Mechanical Inoculation by Tomato spotted wilt virus

Screening of peanut germ plasm for resistance to Tomato spotted wilt virus (TSWV) has been largely inefficient due to the lack of a screening technique based on mechanical transmission of the virus under controlled environmental conditions. We have studied the reaction of three peanut cultivars (Georgia Green, Georgia Runner, C-99R) and one breeding line (C11-2-39) using a highly efficient mechanical inoculation procedure. The disease response was studied at two temperature regimes, 25 to 30°C (low temperature) and 30 to 37°C (high temperature). Based on percent transmission, symptomatology, distribution of TSWV, and relative levels of TSWV nucleocapsid (N) protein, Georgia Runner and Georgia Green were found to be susceptible, whereas C-99R and C11-2-39 were resistant. Of the four genotypes tested, C11-2-39 had the highest level of resistance to TSWV. The results correlated with the field performance of the genotypes except in the case of Georgia Green, which could not be distinguished from TSWV-susceptible Georgia Runner. Exposure of the inoculated plants to higher temperature (30 to 37°C) resulted in a better resistant response as reflected by reduced systemic infection, localized symptom expression, restricted viral movement, and reduced levels of TSWV antigen. To our knowledge, this is the first report of differential response of peanut genotypes to TSWV using mechanical inoculation. The four peanut genotypes should be useful as reference standards for the initial screening and identification of sources of TSWV resistance in peanut germ plasm.

A regression approach for comparing field resistance of peanut cultivars to tomato spotted wilt tospovirus

Relationships between one TSWV susceptible peanut cultivar (Georgia Runner), one moderately resistant peanut cultivar (C-99R), and the current standard cultivar (Georgia Green) in the southeastern United States were examined. Both moderately resistant cultivars had greater field resistance and higher yields than the susceptible cultivar, Georgia Runner, regardless of the level of disease pressure. Linear regression revealed that under heavy disease pressure, C-99R appears to exhibit greater disease resistance than has been previously reported for Georgia Green and other currently available cultivars. Only 13% and 33% of the variation in yield difference between cultivars could be explained by differences in TSWV incidence for C-99R and Georgia Runner, respectively, when compared by linear regression with Georgia Green. Although the correlations were weak for these relationships, the relationships were still significant (P<0.05). Linear regression equations allow us to designate TSWV risk assesment index scores for cultivars relative to scores for the standard Georgia Green. Such a comparison allows for an examination of the relative levels of resistance observed among cultivars under varying levels of disease pressure. This type of analysis would be most useful under heavy disease pressure situations, when the predictive power of this analysis is greater and differences in field resistance between cultivars would be most significant.

Aspergillus colonization and aflatoxin contamination in peanut genotypes with reduced linoleic acid composition.

Aspergillus flavus and A. parasiticus can contaminate several agricultural crops with the toxic fungal metabolite aflatoxin. Previous research has indicated that resistance may be conferred by altering the fatty acid composition of these crops. Recently, peanut breeding lines with reduced linoleic acid content have been developed. The purpose of this study was to examine the effect of reduced linoleic acid composition on preharvest aflatoxin contamination of peanut. Seven breeding lines with relatively low linoleic acid and two check genotypes were grown in a randomized complete block design with 10 replicates for 4 years in Georgia and for 3 years in Arizona. The plots were inoculated with a mixture of A. flavus and A. parasiticus about 60 days after planting and subjected to drought and heat stress for the 40 days immediately preceding harvest. Differences were observed in only one environment. Low linoleic acid composition had no measurable effect on preharvest aflatoxin contamination in peanut when data were combined across years and locations. Products of the lipoxygenase pathway that have been shown to affect aflatoxin biosynthesis in vitro may not be present in sufficient quantities in peanut.

Crystalline Amino Acid Supplementation of Grain Sorghum-Based Low Protein Diets for Growing-Finishing Pigs

Abstract Myer, R.O. and Gorbet, D.W. 2004. Crystalline amino acid supplementation of grain sorghum-based low protein diets for growing-finishing pigs. J. Appl. Anim. Res., 25: 85–90. A study was conducted to evaluate the effectiveness of crystalline lysine, threonine, methionine and tryptophan supplementation of grain sorghum based, low protein diets for growing and finishing pigs (from 31 to 114 kg avg. body wt.). Three similar trials, each with 60 crossbred pigs were done and each involved a comparison of nutritionally adequate grain sorghum-based diets formulated with 1) soybean meal (47%) as the supplemental source of amino acids (control) or with 2) L-lysine HCl, L-threonine, DL-methionine and L-tryptophan plus enough soybean meal to meet the requirements of the other amino acids. Overall, dietary treatment had no effect (P>0.10) on average daily gain, average daily feed intake, feed conversion efficiency, average loin area, backfat thickness or estimated carcass lean percentage. Overall average daily lean gain, however, was lower (P<0.10) for pigs fed the low protein, amino acid supplemented diets compared to pigs fed the control diet. Results indicated that the diet crude protein concentration can be reduced substantially upon amino acid supplementation with no detrimental effect on pig growth performance, however, there was some evidence of decreased lean gain.

Molecular marker screening of peanut ( Arachis hypogaea L.) germplasm for Meloidogyne arenaria resistance

A restriction fragment length polymorphism (RFLP) marker linked to a locus for resistance to Meloidogyne arenaria (Neal) Chitwood race 1, along with visual evaluation following root staining were used to screen four breeding populations and three lines of peanut ( Arachis hypogaea L.) in a root-knot nematode infested field. COAN and Florunner peanut cultivars were used as resistant and susceptible controls, respectively. Genomic DNA was isolated from young leaves of plants during the growing season, and Southern blot analysis was conducted using RFLP probe R2430E. Only COAN and the line TP301-1-8 were homozygous for the resistance marker. During evaluation, root masses were counted and the resistance phenotype scored. This field data confirmed the RFLP marker results. Except for COAN and TP301-1-8, all other genotypes displayed high levels of nematode reproduction. The RFLP probe R2430E provided a useful marker for identifying resistance to the peanut root-knot nematode. Keywords: Arachis hypogaea L., genetics, host resistance, Meloidogyne spp., molecular markers, peanut root-knot nematode. African Journal of Biotechnology , Vol 13(26) 2608-2612