ABSTRACT Six Virginia-type peanut ( Arachis hypogaea L.) cultivars and their paired backcross-derived high-oleate lines were grown during 2003 and 2004 in North Carolina to compare standard germination (SG), cool germination (CG), and electrical conductivity (EC) of seed. Oleic acid level had no influence on SG but did alter CG and EC compared to the corresponding normal oleate cultivars. Averaged across background genotypes, high-oleate lines had lower seed vigor than their paired lines with normal oleic content. The high-oleate lines of three of the six pairs had lower CG and higher EC. Planting and harvest date affected all the seed quality traits measured. Standard germination of both normal and high-oleate lines was reduced in 2004 when harvest was delayed, but was not affected in 2003. In 2003, CG of the high-oleate lines was lower than that of normal lines in three of the four production environments; EC was higher in the high-oleate lines in all planting date and harvest date combinations. In 2004, there was no difference between the CG of normal and high-oleate lines, but EC was higher in the high-oleate lines for three of the four environments. In the greenhouse, the Virginia-type cultivars NC-V 11 and Gregory, along with their paired backcross-derived high-oleate lines were compared at 22/18 C, 26/22 C and 30/26 C day/night temperature regimes. Seed oleic to linoleic acid (O/L) ratio of normal peanut grown in 30/26 C, 26/22 C, and 22/18 C, measured 1.9, 1.5, and 1.3, respectively. The O/L ratio for their high-oleate pairs decreased from 24.7 when grown in 30/26 C to 15.9 in 26/22 C and to 13.7 in 22/18 C. Temperature did not affect the fatty acid composition of axis total lipid or phospholipid fractions. The high-oleate trait was expressed in the axis lipids. The average O/L ratio of axes from normal peanut was 1.1 while that of high-oleate lines was 4.6. Likewise, axis phospholipids for normal and high-oleate lines were 1.0 and 5.9. A lower production environment temperature decreased the O/L ratio of seed oil of high-oleic peanut lines, and the high-oleate trait expressed in peanut seed storage lipids is also expressed in axis membrane lipids to a lesser degree.

ABSTRACT Peanut ( Arachis hypogaea L.) is mostly grown under rainfed production with water deficit being the major limiting factor. Several physiological characteristics have been proposed as surrogates for yield and genotypic selection under water deficit in arid climates, but their suitability for selection under sub-humid rainfed production where water deficit can also occur is not clear. Canopy temperature depression (CTD), specific leaf area (SLA), and SPAD chlorophyll reading of eight virginia-type peanut genotypes were evaluated at three growth stages in field trials involving rainfed and irrigated plants in sub-humid environments in northeastern Virginia-Carolina (VC) region in 2011 and 2012. Significant (p≤0.05) variation in pod yield and all physiological characteristics was observed in response to water regime in both years. Rainfed plants had warmer (CTD 2.2 vs. 3.1 °C) and greener canopies in 2011 but cooler (CTD 3.9 vs. 2.2 °C) and less green canopies in 2012 than the irrigated plants. Compared to irrigated plants, rainfed plants had slightly increased SLA in 2011 (135 vs. 131 cm 2 g −1 ), but decreased SLA in 2012 (133 vs. 144 cm 2 g −1 ). Differences (p≤0.05) among genotypes were observed for pod yield, SLA, and SPAD chlorophyll reading, but not for CTD. Among the physiological characteristics, only SPAD chlorophyll readings were significantly correlated to pod yield in all water regimes and growth stages in 2012, but not in 2011. Based on these results, CTD, SLA, and SPAD chlorophyll reading appear to be unsuited for genotypic selection for yield and water-deficit tolerance for peanut grown in sub-humid environment of the Virginia-Carolina region in part due to unpredictable rainfall amount and distribution. For reproducible field evaluations, additional methods will have to be used such as use of rain exclusion shelters.

ABSTRACT Entry means from 88 trials of runner- and virginia-type peanuts ( Arachis hypogaea L.) conducted over 16 years and three locations in the state of Georgia with an irrigated and a non-irrigated test performed at each year-location combination were examined to determine the mean performance for cultivars and breeding lines and to determine if they exhibit interaction with water regimes. All lines responded positively to irrigation for pod yield, total sound mature kernels (TSMK), 100-seed weight, and estimated support price and dollar value. Runner cultivars generally performed better in Georgia than did virginias although some virginia cultivars developed in Georgia were competitive with superior runners. The runner cultivar with the greatest value per hectare in this study was Georgia-12Y; the virginia cultivars were Georgia-08V and Georgia-11J. There was interaction between water regimes and entries for all reported traits except estimated dollar value. For pod yield and 100-seed weight the interaction was solely between water regimes and market types, for TSMK and length of season it was solely between water regimes and entries within market types, and for estimated support price it was both. In general, the effect of irrigation was more substantial on grade of virginia market-types than it was on runners while runners responded more to irrigation for pod yield than did virginias (982 vs. 782 kg ha −1 , P<0.0169). Interaction of water regimes with specific entries within market types was in the main a matter of varying degree of effect of irrigation on specific lines but all in the same general direction. The exception was length of season which actually increased under irrigation for the most recent Univ. of Georgia releases, Georgia-10T, Georgia-11J, and Georgia-12Y, while irrigation hastened the maturity of all other lines.

ABSTRACT Wild Arachis species from section Arachis have been promoted as sources of resistance to common peanut diseases and insect pests. The objective of our study was to identify wild Arachis species with resistance to Sclerotinia blight and Cylindrocladium black rot (CBR). One hundred and ten accessions/entries from 23 Arachis species including A. hypogaea were evaluated in the greenhouses at North Carolina State University between January and March of 2010 in a 11×10 rectangular lattice experimental design with 4 replications for Sclerotinia blight and 6 replications for CBR. For the Sclerotinia blight test, seeds were planted in 10 cm clay pots and 8-wk-old plants were inoculated in a mist chamber with BEEM capsules containing the fungus inserted on the petioles of the 4 th leaf from the apex on the primary branch. Lesion lengths were measured 4, 5, 6, and 7 d after inoculation, and areas under the disease progress curves (AUDPC) were calculated. For the CBR test, seeds were planted in soil mixed with microsclerotia (25/g) in cone-tainers partly immersed in water. Root damage was recorded after 60 d on a 0–5 proportional scale (0 = no decay to 5 = completely decayed). Data analysis indicated significant (p<0.05) variation among and within Arachis species for both diseases. Arachis glandulifera exhibited the highest level of Sclerotinia blight resistance followed by A. correntina, A. herzogii, and A. helodes , although the last three species were not significantly different from A. hypogaea . Overall, low genetic variability for Sclerotinia blight resistance was observed among the wild species accessions. For CBR, A. valida, A. cruziana , A. microsperma , A. williamsii , A. kempff-mercadoi , A. kuhlmannii , A. helodes , A. cardenasii and A. correntina formed the most resistant group with A. hypogaea in the most susceptible group. Overall, significant genetic variability for CBR resistance was found among the different wild species accessions. However, not all accessions within a species were resistant to either disease, and most accessions that were resistant to one disease were susceptible to the other.

ABSTRACT The identification of molecular markers for economically significant traits should greatly improve the speed and efficiency of all peanut ( Arachis hypogaea L.) breeding programs. Development and phenotypic evaluation of recombinant inbred line (RIL) populations of peanut, along with molecular genotyping, will be essential for association of markers with traits. The primary objectives of this research were to develop 16 structured RIL populations that can be used by the peanut research community, and to begin high-resolution phenotyping of these populations. Crosses were made using a 2 by 8 (common by unique) factorial nested association mapping design. Parents were selected to attempt to maximize genetic diversity while meeting practical breeding objectives. First, two modern runner cultivars (Tifrunner and Florida-07) were selected as common parents because runner cultivars account for about 80% of the production in the U.S. Second, the eight unique parents were selected to supply diversity across market classes and botanical varieties and are donors of favorable alleles for enhancing drought tolerance and resistance to most important disease of peanut in the U.S. The eight unique parents are N08082olJCT (a Bailey derived high oleic breeding line), C76-16, NC 3033, SPT 06-06, SSD 6 (PI 576638), OLin, New Mexico Valencia A, and Florunner. The 16 populations were advanced using summer and winter nurseries. Input from multiple disciplines has resulted in a prioritized list of populations and traits that should be examined, and seed increase has begun to provide the community with material for extensive phenotyping. In-depth phenotyping and genotyping of these populations should result in markers that can be deployed by breeding programs for the development of improved cultivars.

ABSTRACT Tomato spotted wilt (TSW) caused by Tomato spotted wilt tospovirus (TSWV) has become a serious constraint to peanut ( Arachis hypogaea L.) production in the Virginia-Carolina production area. Regression stability analysis was applied to TSW incidence data collected in 64 trials conducted over 17 years to determine if an array of 31 virginia-type cultivars and breeding lines exhibited variation in their reactions to increasing levels of general TSW intensity compared with the standard field-resistant cultivar Georgia Green and hirsuta-type line PI 576636. Eight cultivars (NC 7, NC 9, NC 10C, NC-V 11, NC 12C, Perry, Phillips, and Brantley) had mean effects greater than zero (P<0.01) while Bailey, four Bailey siblings, and N96076L, Bailey's resistant parent, all had mean effects less than zero (P<0.01). The deviations of the slope of regression on environmental index (β̂ k ) for four of the eight susceptible cultivars were greater than zero, indicating greater than average reaction to increased levels of TSW. The β̂ k for Bailey indicated that its response to increasing levels of TSW was flat. PI 576636 was confirmed as a highly field-resistant line. The slopes of Georgia Green, the standard TSWV-resistant runner-type cultivar, the Bailey siblings and N96076L did not differ from the average of all lines. The correlation between mean effect and β̂ k was r = 0.693, indicating that approximately half the variation in β̂ k could be explained by mean effects. However, the regression analysis provided information useful in describing the TSW reactions of the lines and cultivars.

Differences in the ability of cultivars to compete with weeds are not well-defined for peanut. Research was conducted in 2007 and 2008 to compare the growth and competitiveness of the virginia market type cultivars NC 10C, NC-V 11, NC 12C, Phillips, VA 98R, and breeding lines N99027L, N01013T, and N02020J under weedy and weed-free conditions. Weed-free peanut was established by applying preemergence and postemergence herbicides throughout the growing season supplemented by weekly hand removal of weeds. Clethodim was applied to weedy peanut to eliminate annual grass interference but not interference from broadleaf weeds and sedges. Weed-free peanut biomass, weedy peanut biomass, and weed biomass were not affected by genotype 10 weeks after peanut emergence. Although substantial yield loss was noted in presence of weeds, the percent yield loss did not vary by genotype when comparing weedy and weed-free yield. These data suggest that cultivar selection within virginia market type peanut will have limited utility in a comprehensive weed management strategy.

Peanuts ( Arachis hypogaea L.) are known to be a source of several important B-vitamins, including niacin (Vitamin B3). A total of 39 Florunner and NC7 samples from the 2007 and 2008 Uniform Peanut Performance Test (UPPT) were analyzed to compare their niacin content from 10 different growing locations in the U.S. From the Core of the Core of the peanut germplasm collection, 13 selected samples grown in North Carolina in 2008 were analyzed. Over 2 years and 10 locations, raw Florunner niacin levels ranged from 8.8 to 21.9 mg/100g DW. Mean niacin concentration in 2007 was 15.7 mg/100g DW and 17.8 mg/100g DW in 2008. Raw samples of NC7 averaged 19.0 mg/100g DW in 2007 and 20.3 mg/100g DW in 2008. The varietal difference was statistically significant as were differences among growing locations. The lowest niacin levels were found in the Virginia-Carolina region and the highest in Texas and Oklahoma. Although the 2008 niacin means were higher than 2007, the increase was not statistically significant. Roasting raw 2008 samples caused niacin levels to drop 12% (p = 0.0212) in Florunner and 6% in NC7 (p = 0.0128). Mean niacin concentrations in the Core of the Core samples were found to range from 13.9 to 20.7 mg/100g DW. Levels of niacin in the Core samples tested were found to be higher than Florunner (12.2 mg/100 DW) and NC7 samples (13.8 mg/100g DW) grown at the same location and in the same year. Significant differences in niacin content among NC7 and Florunner UPPT entries across 10 locations indicated a potential for genetic variation that is potentially exploitable by breeders. This is supported by the significant differences found among the Core of the Core entries and NC7 and Florunner samples from the same location and year.

Disease resistant cultivars with good quality are needed by U.S. peanut growers to lower production costs. In the Virginia-Carolina (V-C) production area, use of resistant cultivars to reduce leaf spots would be a cost-effective and environmentally safe alternative to chemical applications. Twenty-six interspecific hybrid derived breeding lines with 5 Arachis species in their pedigrees, six resistant A. hypogaea checks and 11 susceptible cultivars were evaluated for leaf spot resistance in field tests at the Peanut Belt Research Station in Lewiston, NC from 2004 to 2006 without leaf spot fungicides. Defoliation was rated on a 1–9 proportional scale with 1 = no defoliation (resistant) and a 9 = complete defoliation (susceptible). The mean defoliation score of the cultivars was 6.8±0.1 (range = 6.4 to 7.4), compared to 5.3±0.1 (range = 4.4 to 6.3) for the interspecific hybrid derived breeding lines. Some of the interspecific hybrid derived breeding lines showed levels of leaf spot resistance similar to the resistant A. hypogaea checks (mean = 4.3±0.2), suggesting that these breeding lines contain genes conditioning resistance to the leaf spots. The combined mean yield of the cultivars was 2709±103 kg/ha (range = 2296 kg/ha to 3070 kg/ha), whereas that of the interspecific hybrid derived breeding lines was 3169±119 kg/ha (range = 2467 kg/ha to 3767 kg/ha). Evaluation of selected grade characteristics showed that several interspecific hybrid derived breeding lines have grade similar to those of the commercial cultivars. Sixteen of the 26 interspecific hybrid derived breeding lines with five different diploid species in their pedigrees and NC 7, the commercial flavor standard for the V-C area, were also evaluated for sensory quality. No significant variation among test entries was found for the roasted peanut, sweet, or bitter sensory attributes. This suggests that high levels of leaf spot resistance can be combined with superior yield, grade and other quality factors and that some of these lines may become useful for commercial production in the V-C area.

Peanut composition is influenced by several groups of factors: environmental, genetic, and their interaction. This study evaluated the relative contributions of these factors using data from the USDA-ARS quality testing program using samples from the multi-state Uniform Peanut Performance Tests (UPPT). Data were subjected to restricted maximum likelihood estimation of variance components reflecting the main effects of year, production region, location within region, genotype (cultivar or breeding line), and kernel grade (“seed size”) within genotype, and the interactions among these main effects. Genetic variation in oil content was low (9% of total variation); however, fatty acid composition of the oil was highly influenced by genotype (34–77%) with the exception of lignoceric acid (1%). Genetic influence on tocopherols was generally less than that of fatty acids. Environmental variation of tocopherols was greater than the variation attributable to genotype-by-environment interaction. The lowest genetic variation was observed in sugar content; however, environmental variation was high (68%). The magnitude of genetic influence on oil content and fatty acid concentrations suggests that these traits are amenable to improvement through breeding.

Several diploid wild species of the genus Arachis L. have been used as sources of resistance to common diseases of cultivated peanut ( Arachis hypogaea L.). Because flavor is among the most important quality attributes for commercial acceptance of roasted peanuts, sensory attributes of interspecific hybrid derived breeding lines were evaluated to determine if transfer of disease resistance from wild species is associated with concomitant changes in flavor. Sixteen interspecific hybrid derivatives with five diploid species in their ancestries and the commercial flavor standard, NC 7 were evaluated for sensory quality. Significant variation among entries was found for the roasted peanut, sweet, and bitter sensory attributes, but not for the overall contrast between NC 7 and the wild species-derived breeding lines. The variation was either between two groups of wild species-derived breeding lines or within one or both groups. Introduction of disease and pest resistance traits from Arachis species did not result in degradation or improvement of the flavor profile. This suggests that flavor of wild species-derived germplasm will not prevent its use either as parents in peanut breeding programs or as cultivars.

Tomato spotted wilt virus (TSWV), a thrips-vectored tospovirus , is an important pathogen of peanut ( Arachis hypogaea L.). Development of tolerant cultivars has proven to be one of the most promising methods to manage the disease. Twenty-four genotypes of virginia market-type peanut were monitored in field tests for thrips damage, and TSWV incidence and severity during 2004 and 2005 in North Carolina. The cultivar Gregory had a higher density of adult thrips in foliage than any other genotype, while breeding lines N01057 and N03054E had the lowest density. No significant correlation was detected between thrips density or injury and TSWV incidence. Line N03036EJ had the greatest TSWV incidence, but did not differ from cultivars Gregory or Perry in incidence. Line N00033 had the least TSWV incidence and differed from the cultivars Gregory and Perry. The occurrence of late-season chlorosis or peanut yellowing death (PYD) was highly correlated with TSWV infection (P < 0.0001). Breeding line N02051ol had the greatest incidence of PYD, but did not differ statistically from Gregory or Perry. Lines N03023EF and N01083 had the least PYD incidence. Plants infected with TSWV not expressing foliar symptoms were found in far greater abundance than plants that were infected and symptomatic. Line N03036EJ had the greatest proportion of infected but asymptomatic plants; line N03054E had the least. Susceptible lines are more likely to become infected, rather than just more likely to show spotted wilt symptoms.

Peanut flavor is influenced by several groups of factors: environmental, genetic, and interaction between them. This study evaluated the relative contributions of these factors using data from the USDA-ARS program of sensory quality testing of samples from the multi-state Uniform Peanut Performance Tests (UPPT). Data were subjected to restricted maximum likelihood estimation of variance components reflecting the main effects of year, production region, location within regions, genotype, and kernel grade within genotype, and the interactions among these main effects. Genetic variation was relatively small (0.0 to 9.5% of total variation) while environmental variation, particularly that due to years, was large. Year-by-genotype interaction was large for roast color and intensities of the roasted peanut and sweet aromatic attributes. Estimates of repeatability (R) for sensory attributes were low, even based on means measured across multiple locations and two years, except for that of the sweet attribute (R = 0.10 for a single observation and R = 0.34 for a mean across two years of UPPT testing). Breeders should be able to reliably identify lines with superior sweet attribute intensity, but identification of lines with intense roasted peanut attribute will be more difficult.

Cylindrocladium black rot (CBR) caused by Cylindrocladium parasiticum and Sclerotinia blight caused by Sclerotinia minor are two economically important diseases of peanut ( Arachis hypogaea ) in the Virginia-Carolina production area. Developing cultivars with resistance to both diseases requires screening of new peanut breeding lines for resistance. Because field evaluations of resistance to these diseases often fail to produce usable results, greenhouse protocols were used to screen breeding lines and cultivars for resistance. For CBR, two seeds of a genotype were planted in a “cone-tainer” filled with a planting medium artificially infested with 25 microsclerotia of C. parasiticum per g of medium. After approximately 8 wk, the roots were washed and rated for degree of decay on a 0–5 proportional scale (0 = no decay to 5 = completely decayed). For Sclerotinia blight, plants were inoculated at 6 wk after planting by pushing a plug of potato dextrose agar (PDA) colonized by S. minor and protected from desiccation in a BEEM embedding capsule onto a freshly cut petiole on the main stem of the plant. Inoculated plants were placed in a mist chamber to maintain the high humidity necessary for infection. Lesion lengths were measured 4, 5, 6, and 7 days after inoculation, and areas under the disease progress curves (AUDPC) were calculated. All tests were conducted as incomplete block designs with six replications for CBR tests and four replications for Sclerotinia blight tests. Adjusted entry means were computed from each year's tests and used in summary analyses. Of the 125 breeding lines and checks tested at least once from 2003 through 2006, 51 were tested in at least two years, 34 in at least three years, and 15 lines were tested in all four years. Of the 15 lines tested in all four years, registered germplasm line N96076L had the lowest AUDPC for Sclerotinia blight (58 mm days), but had the greatest CBR root decay score (4.1 decay rating units). Several closely related breeding lines descended from a cross of N96076L and NC 12C were not significantly different from the most resistant line for either disease with scores ranging from 2.2–3.0 decay rating units for CBR and 63–99 mm days for Sclerotinia blight. Correlations of multiple-year greenhouse assay means with field disease incidence means were 0.83 for CBR and 0.35 for Sclerotinia blight. The greenhouse assay for CBR was a reasonably good predictor of field performance, but the assay for Sclerotinia blight was less reliable as a predictor.

The objective of this study was to empirically estimate the combining abilities of peanut ( Arachis hypogaea L.) lines for sensory quality and to compare those combining abilities with best linear unbiased predictors (BLUPs) of breeding value and with mean performance of the parents as lines per se . Eleven cultivars and breeding lines were chosen for use as parents of a half-diallel cross, nine on the basis of BLUPs of breeding value for the roasted peanut, sweet, and bitter sensory attributes. Bulk F 4 populations from 33 crosses were grown in a replicated field trial at Lewiston, NC in 2004. An SMK sample from each plot was roasted, ground to paste, and evaluated by an eight-member, trained sensory panel. There was significant variation among test entries, among crosses, and among general combining abilities (GCAs) for intensity of the roasted peanut and sweet sensory attributes, but not for bitter. UF714021, a component of the Altika cultivar, was the best parent for improvement of roasted peanut and bitter attribute intensities and the old spanish-type cultivar Pearl for improvement of sweet. There were, however, several other parents not significantly different from these for each of the attributes. Correlations of the empirically determined GCAs with the previously predicted BLUPs of breeding values were positive but moderate in magnitude. For roasted peanut, adjusted genotypic means were slightly superior to the BLUPs as indicators of GCA while for sweet and bitter the BLUPs were slightly superior.

Spotted wilt of peanut ( Arachis hypogaea L.), caused by the tomato spotted wilt virus (TSWV), has progressively become more prevalent in the Virginia-Carolina production area. Management tactics for control of spotted wilt are limited. Development of cultivars with moderate to high levels of field resistance to TSWV is the most promising means of managing the disease. Breeding efficiency can be maximized by choosing parents based on their potential to produce superior progeny. Best linear unbiased prediction (BLUP) is a method for estimating the breeding value of a parent based on its own performance as well as that of its relatives. The objective of this study was to investigate the use of BLUP to identify lines with superior ability to transmit decreased TSWV field incidence to their progeny. The data set used included 118 breeding lines, 12 cultivars and one hirsuta -type ( A. hypogaea subsp. hypogaea var. hirsuta Köhler) accession. Data on TSWV incidence were obtained from trials representing three locations and six years and on agronomic traits from trials at three locations and 13 years. Because only estimates of broad-sense heritability (H) were available, BLUPs were computed using a range of estimates for narrow sense heritability (h 2 ). BLUP of breeding value for TSWV incidence obtained with different estimates of h 2 were highly correlated (r > 0.85), indicating that BLUPs are not critically affected by inaccurate estimates of h 2 . Breeding values predicted by BLUP were moderately correlated (0.54 < r < 0.83) with line means estimated from a fixed-effect model. Specific lines with favorable breeding values for TSWV incidence included a set of lines resistant to early leafspot ( Cercospora arachidicola Hori) and the hirsuta accession, PI 576636. BLUPs for yield, meat content, crop value, and pod brightness also were calculated. Six different weighting schemes were used for index selection in order to pick lines with superior breeding values for a combination of all traits analyzed. Thirteen lines were selected with four or more of the six weighting schemes, suggesting that these lines should be able to transmit to their progenies not only reduced TSWV incidence, but also increased yields and improved quality traits.

Tomato spotted wilt, caused by Tomato spotted wilt tospovirus (TSWV) is a major problem in peanut ( Arachis hypogaea L.) producing areas of the southeastern U.S. The integrated program used to manage spotted wilt relies heavily on cultivars with field resistance to TSWV, and finding new sources and greater levels of resistance to TSWV is highly desirable. Field tests were conducted in 2003 and 2004 in Marianna, FL and Tifton, GA to compare three peanut breeding lines, F NC94022-1-2-1-1-b3-B, C 11-2-39, and C 11-186 to that of standard moderately resistant cultivar Georgia Green for field response to TSWV. F NC94022-1-2-1-1-b3-B was of particular interest because it was developed from a cross between lines of A. hypogaea subsp. hypogaea var. hirsuta Köhler and A. hypogaea subsp. hypogaea var. hypogaea . In all tests, final spotted wilt ratings for breeding lines F NC94022-1-2-1-1-b3-B, C 11-2-39, and C 11-186 were lower and pod yields were higher than for Georgia Green. In three tests, final spotted wilt intensity ratings did not differ among F NC94022-1-2-1-1-b3-B, C 11-2-39, and C 11-186. At Marianna in 2004, spotted wilt intensity ratings were lower and pod yields were higher in F NC94022-1-2-1-1-b3-B than in any other entry. The high level of field resistance to TSWV in F NC94022-1-2-1-1-b3-B is presumably derived from its hirsuta type parent, PI 576638.

Contamination of peanut ( Arachis hypogaea L.) with aflatoxin produced by species of Aspergillus remains a problem for the U.S. peanut industry. Several peanut genotypes were reported to be resistant to in vitro seed colonization by Aspergillus flavus Link ex Fries (IVSCAF), to field seed colonization by A. flavus (FSCAF), or to preharvest aflatoxin contamination (PAC), but few to production of aflatoxin per se. Cotyledons of 39 peanut genotypes reportedly resistant to IVSCAF, FSCAF, or PAC, and eight susceptible to PAC were evaluated in four tests for their ability to support aflatoxin production after inoculation with A. flavus. Cultivars Perry and Gregory were used as checks in each test. Seed cotyledons were separated, manually blanched, inoculated with conidia of A. flavus , placed on moistened filter paper in petri dishes, and incubated for 8 d at 28 C. Dishes were arranged on plastic trays enclosed in plastic bags and stacked with PVC spacers between trays. Incomplete block designs were used for all tests. In each test, none of the genotypes examined was completely resistant to aflatoxin production, but significant genotypic variation was observed in the amount of total aflatoxin accumulated in seeds. Genotypes previously reported to be resistant to IVSCAF, FSCAF, or PAC exhibited differential abilities to support aflatoxin production. PI 590325, PI 590299, PI 290626, and PI 337409 supported reduced levels of aflatoxin, and their degree of resistance was consistent across tests. Fungal growth was highly correlated with aflatoxin production in three tests. The results from this study suggested that there were no absolute relationships of aflatoxin production resistance with IVSCAF, FSCAF, or PAC resistance, but that it should be possible to identify a genotype with high IVSCAF, FSCAF, or PAC resistance and reduced capacity for aflatoxin production by A. flavus.

Anatoxins are carcinogenic and extremely toxic secondary metabolites produced primarily by two fungi, Aspergillus flavus Link ex Fries and A. parasiticus Speare. Elimination of aflatoxin contamination in peanut ( Arachis hypogaea L.) is a high priority of the peanut industry. Resistant cultivars should be an effective and low-cost part of an integrated aflatoxin management program. To date, no cultivated peanut has been reported with stable high levels of resistance to aflatoxin production. Arachis species and interspecific tetraploid lines have been evaluated for resistance to several peanut diseases and insect pests, and highly resistant accessions have been reported. Seven accessions of A. cardenasii Krapov. and W.C. Gregory, 29 of A. duranensis Krapov. and W.C. Gregory, and 17 interspecific tetraploid lines derived from A. hypogaea × A. cardenasii were inoculated with A. flavus strain NRRL 3357 and analyzed for aflatoxin content after incubation. On average, A. duranensis and A. cardenasii accumulated significantly less aflatoxin than A. hypogaea checks. The mean difference between the two wild species was not significant. Arachis duranensis accessions PI 468319 (GKBSPSc 30073), PI 468200 (GKBSPSc 30064), and PI 262133 (GKP 10038 sl.); and A. cardenasii accessions PI 262141 (GKP 10017) and PI 475997 (KSSc 36018) had reduced levels of aflatoxin accumulation and should be valuable sources of resistance to aflatoxin contamination. Of the interspecific tetraploid lines, only GP-NC WS 2 supported aflatoxin production not significantly different from resistant parent A. cardenasii GKP 10017, and it appears to be a line with reduced capacity for aflatoxin accumulation.

Enhancement of flavor of roasted peanut ( Arachis hypogaea L.) has been a long-standing objective of the peanut industry. Studies relative to roasted peanut flavor variation have separated the effects of genotype, environment, and genotype-by-environment interaction on the sensory attributes roasted peanut, sweet, bitter, and astringent. Much of the focus of these studies has been on the genotypic variation and the possibility of genetic improvement of peanut flavor. However, most of the variation in sensory attributes is caused by non-genetic factors. Years were found to be the largest single source of variation for the sensory attributes roasted peanut and bitter. Because roasted peanut is the sensory attribute most important to the peanut consumer, it is important to know if the observed year effects varied randomly or if there was any directional trend in peanut flavor over time. Examination of a 15-yr data set for directional trends in peanut flavor indicated that all three sensory attributes (roasted peanut, sweet, and bitter) exhibited adverse trends across the span of this study. These trends were independent of whether or not the effects of years were unadjusted for other effects or adjusted for the effects of regions, locations within regions, and the covariates fruity attribute intensity and roast color. The nature of the evident trends, i.e., whether they were linear or curvilinear, was often affected by adjustment. Changes in sensory quality of a single cultivar over time are likely due to changes in prevailing cultural practices such as rotations and chemicals applied to the peanut crop. It was not clear whether consumers would have noticed the change in sensory quality over time because the trends within individual cultivars were confounded with changes in the dominant runner-type cultivars with variable sensory quality marketed over the span of the study.