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 4th 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 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 Peanut (Arachis hypogaea L.) is an important crop in the Virginia-Carolina (VC) region. Virginia-type cultivars are preferred vs. other peanut types because of the in-shell and gourmet markets that evolved in the VC region around this peanut type. Reduced federal support coupled with increased production costs for the virginia-type peanut vs. other peanut types and recently higher fuel and pesticide prices are good reasons for farmers to consider growing other peanut types than virginia-type in the VC region. Earlier research suggested that runner-type peanut can provide yield, gross value, and economic return similar with virginia-type when grown in the VC region. However, direct comparison of runner and virginia-type cultivars needs to be updated as new cultivars become available. In this study we compared four runner-types with five virginia-type cultivars for plant development, disease incidence, pod yield, pod brightness, grade factors, and gross value in 2009 and 2010. In agreement with earlier findings, the results show that runner-types can provide similar gross returns with virginia-type peanut cultivars when grown in the northern VC region. Florida 07 runner and Bailey virginia-type, currently the most popular cultivars in the VC region, had high yields and gross values in both years. However, Florida 07 and other runners matured later and pods were less bright when compared with the virginia-types. Therefore, growing runners in the northern VC region may be challenging due shorter seasons and reduced pod brightness if peanut is used for in-shell markets.

Abstract A five-year study to investigate the potential interaction of conservation tillage with reduced irrigation amounts was conducted near Dawson, GA on peanut (Arachis hypogaea L.). Conventional tillage was compared to two conservation tillage programs (wide-strip and narrow-strip tillage) under four irrigation levels (100, 66, 33, and 0% of a recommended amount). Peanut yield did not exhibit a tillage by irrigation interaction as expected, although the main effects of irrigation and tillage were each significant by year due to weather variations. Peanut yield in narrow-strip tillage or wide-strip tillage were individually superior to conventional tillage in three seasons out of five, however only in one year did both conservation tillage systems outperform the conventional system. No detrimental effects on yields could be attributed to conservation tillage. Peanut quality and digging loss were dependent on the tillage by year effect as well as the main effect of irrigation. Irrigation increased total sound mature kernels (TSMK) 2% versus non-irrigated (0% irrigation level); tillage was not significant each year of the study but increased TSMK 2% in three of five years. Digging losses were greater in plots with increased yield potential such as those receiving irrigation. Net economic returns revealed a moderate trend towards sustained profitability under reduced irrigation levels through narrow-strip tillage and to a lesser extent, wide-strip tillage. Under conventional tillage systems, returns decreased with decreasing amounts of irrigation applied.

Abstract Tomato spotted wilt, caused by Tomato spotted wilt virus (TSWV) and transmitted by thrips, and early leaf spot and late leaf spot are among the most important diseases of peanut in the southeastern United States. The objective of this study was to compare field susceptibility of diverse peanut lines to TSWV and leaf spot pathogens for selection of lines for mapping population development. In field trials in 2007 and 2008, 22 genotypes were evaluated for reactions to TSWV and leaf spots. Early leaf spot was the predominate pathogen in both years. There was a near-continuous range of spotted wilt from 18% to 79% for the total incidence rating with any symptoms caused by TSWV. In general, NC94022, ‘Georganic’, C689-6-2, ‘Georgia-01R’, C724-19-25, TifGP-1, C11-154-61, C12-3-114-58, and ‘Tifguard’ were among the most resistant genotypes to TSWV, whereas GT-C20, GT-C9 and PE-2 were the most susceptible. Final percentage of defoliation by leaf spots ranged from 10% to 97% for both years. Genotypes C689-2, Georgia-01R, C12-3-114-58, C11-154-61, Tifguard and Georganic showed resistance to leaf spots, whereas ‘NC-6’, ‘Spancross’, GT-C9, GT-C20 and PE-2 were susceptible to leaf spots. There were 3 cultivars and 3 breeding lines classified as resistant to both TSWV and leaf spots; and there were 3 genotypes from China susceptible to both TSWV and leaf spots. These phenotypic disease reaction data can be used in conjunction with genetic characterization of these genotypes for development of recombinant inbred line populations in efforts to develop markers for resistance to TSWV and leaf spots.

Abstract 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.

Abstract Research was conducted in Florida in 2005 through 2008 to evaluate weed management systems in narrow (38-cm)- and wide (76-cm)-row peanut. Benghal dayflower control increased when peanut row spacing was narrowed. Paraquat plus bentazon early-postemergence (EPOST) followed by (fb) imazapic or imazethapyr mid-postemergence (MPOST) or chlorimuron late-postmergence (LPOST) controlled Benghal dayflower at least 90%. Imazapic EPOST with or without 2,4-DB MPOST controlled Benghal dayflower 98 to 100%. Diclosulam or flumioxazin preemergence (PRE) fb paraquat plus bentazon EPOST fb 2,4-DB MPOST or either PRE herbicide fb 2,4-DB MPOST did not increase Benghal dayflower control compared with imazapic-containing treatments. Browntop millet control was 98 to 100% for treatments with imazapic or imazethapyr EPOST and control was greater in narrow-row compared to wide-row peanut. All herbicide treatments controlled pitted morningglory at least 90% and peanut row spacing did not influence control. Only treatments with imazapic EPOST as a component controlled sicklepod at least 90%. No difference between peanut row spacing was observed for sicklepod control. Peanut planted in narrow-rows yielded greater than wide-row peanut. Few differences in peanut yield were observed among herbicide treatments, but all herbicide treatments resulted in yields greater than the nontreated control. Data indicates that seeding peanut in narrow-rows will improve Benghal dayflower and browntop millet control and will increase peanut yield compared to wide-row peanut.

Abstract Peanut pasta was created by replacing a portion of the durum wheat flour with peanut flour in a basic pasta formulation. Pasta noodles were made using cold extrusion and forced-air oven drying. An improved formulation and approximate ranges for ingredients were determined through a series of functionality tests. Appropriate water percentage in the dough was found to be 40% for good handling characteristics. A hydrocolloid stabilizer, λ-carrageenan, was useful at levels between 1.5 and 2.9% to enhance dough binding properties and allow the use of peanut flour in greater proportions. The maximum acceptable level for peanut flour replacing durum wheat flour was found to be 50%. Drying pasta to 8% moisture at different temperatures allowed direct comparison of drying temperature effect. Mechanical properties of dried peanut pasta improved with increasing levels of λ-carrageenan in the formula. Peanut pasta containing λ-carrageenan between 2.5 and 2.9% produced the best tensile strength. Pasta color lightness decreased with increasing drying temperature, as well as with increasing levels of peanut flour. An informal sensory evaluation of these products suggested that peanut pasta might be acceptable to consumers and has potential in health food and Asian food markets.

Abstract Field studies were conducted to determine runner type peanut response to glyphosate at 80, 160, 240, 320, and 470 g ae/ha applied 75, 90, and 105 days after planting (DAP) at Plains and Ty Ty Georgia in 2006 and 2007. Data collected included seed kernel mass, peanut pod yield, and seed germination. The two-way interaction between DAP and glyphosate rate was not observed for any variable. Data indicated that glyphosate applied at 75 DAP reduced peanut seed mass to 643 mg/kernel, which was less than the 90 or 105 DAP application masses of 669 and 665 mg/kernel, respectively. This could be attributed to the timing of that application when peanut was in the beginning of pod fill or R3 growth stage of development. Peanut physiological response to glyphosate was reflected in peanut seed mass. As glyphosate dose increased, peanut seed mass decreased. Seed masses following glyphosate at 80, 160, 240, 320, or 470 g/ha were 669, 674, 662, 645, and 625 mg/kernel, respectively, as compared to 678 mg/kernel for the nontreated control. When glyphosate was applied at 80 or 160 g/ha, peanut pod yield was similar to the nontreated control. At glyphosate rates of 240, 320, and 470 g/ha, peanut pod yield was reduced to 88, 76, and 64% of the nontreated control. Peanut pod yield was reflective of the reductions in seed mass with increasing glyphosate rate which reduced yield. Seed germination was 96% and greater, which indicated that glyphosate applied at any rate or timing did not affect viability compared to the nontreated control.

Abstract Fungicide inputs are a costly but critical component of peanut production systems in the southeast U.S. Current strategies for reducing fungicide application numbers that are needed to control diseases on peanut include extending application intervals beyond a 2-wk schedule or implementation of a fungicide advisory, such as AU-Pnuts. In this study, fungicide programs with azoxystrobin, chlorothalonil, and tebuconazole, using different application schedules, were compared for the control of early leaf spot and stem rot. Application schedules were the standard 2-wk calendar interval, extended 3- and 4-wk intervals, and applications were made according to the AU-Pnuts leaf spot advisory. Studies were conducted on the disease resistant cultivars DP-1 in 2003 and C-99R in 2004 and 2005. The numbers of fungicide applications for the 2, 3, and 4-wk schedules were 7, 5, and 4, respectively, in 2003 and 2004, and were 6, 5, and 4, respectively, in 2005. One less fungicide application was scheduled according to AU-Pnuts than with the 2-wk calendar schedule in all three years, yet final early leaf spot levels with these schedules were similar in 2 of 3 years. With one fewer fungicide application, the 3-wk schedule had higher leaf spot levels than the AU-Pnuts advisory in 2003 and 2004. Further, when application intervals were extended from 2 wk to 3 or 4-wk intervals, a significant increase in early leaf spot was noted in two of three years. Despite these differences in early leaf spot severity, application schedule had limited impact on yield in this study. Application interval also had little impact on stem rot incidence, but incidence of this disease was lower with the azoxystrobin than chlorothalonil programs in 2 of 3 years. The azoxystrobin program significantly increased yield in 2 of 3 years compared with the chlorothalonil or tebuconazole programs. Yield was also higher for the tebuconazole compared with chlorothalonil programs in 2 of 3 years. When fungicide product and application costs were calculated, and those and other typical peanut production costs were deducted from estimated returns based on actual yields, the resulting net returns did not significantly differ among fungicide programs or application schedules.