Inter-row plant spacing effects on grain and fodder yields, growth performance, digestibility and manure quality of sheep

In Ghana, peanut (Arachis hypogaea L.) grain and fodder serve as important sources of protein for human and livestock nutrition, respectively. Experiments were conducted in four farming communities to determine the effects of planting annual peanut at four inter-row spacings of 30, 45, 65 and 75 cm on grain and fodder yields (experiment I), growth performance and manure quality (experiment II), and in situ digestibility (experiment III) of Djallonké sheep fed fodder from these plant spacings. Planting peanut at 30 cm inter-row spacing dually increased grain and fodder yields compared to planting at 60, and 75 cm. Peanut fodder from 30 cm inter-row spacing also had comparatively higher concentration of crude protein and lower concentrations of acid detergent fiber and acid detergent lignin, resulting in significant improvements in dry matter digestibility at 48 h and superior average daily weight gain of sheep. The concentration of N excreted in the manure of sheep fed the 30 cm fodder was greater than those fed peanut grown at 60, and 75 cm inter-row spacing. Planting peanut at an inter-row spacing of 30 cm therefore gave dual benefits of increasing grain and fodder yields as well as increasing the digestibility and growth performance of sheep fed peanut fodder as a supplementary diet to natural pasture for 70 days. Higher concentration of N in the manure of sheep fed 30 cm fodder could have additional benefits of improving soil fertility in smallholder farming systems where inorganic fertilizers are expensive and inaccessible to farmers.

Relative Tomato Spotted Wilt Incidence and Field Performance among Peanut Cultivars as Influenced by Different Input Production Practices in Georgia.

During 2017-19, 30 replicated yield trials were conducted to determine relative tomato spotted wilt (TSW) incidence and general field performance among 19 runner and virginia market type peanut (Arachis hypogaea L.) cultivars. Four different input production practices were compared across three Georgia locations (Tifton, Plains, and Midville). Two early-planted (April) field tests were conducted at Tifton and Plains each year. One early-planted trial involved maximum-input practices of recommended pesticides with irrigation, and the other early-planted field trial did not receive any fungicides, insecticides, or irrigation. Early-planted maximum-input production practices with irrigation resulted in the highest percentage of mid-season TSW and late-season total disease incidences while also producing the highest pod yields and dollar values. Two other optimum-planted (May) maximum-input field tests were conducted at Tifton, Plains, and Midville, GA as part of the official statewide variety trials (OVT). These OVT utilized maximum-input production practices of pesticides both with and without irrigation. In the OVT, midseason TSW incidence showed no difference between irrigated and non-irrigated; however, the end-of-season total disease percentages which were predominantly TSW did show significantly higher disease percentage, produced the highest pod yields and dollar values within the irrigated field tests compared to the non-irrigated tests. In the overall four tests comparison, disease results showed significantly lower TSW incidence in the early-planted tests without fungicides and insecticides input production practices and no-irrigation; whereas, both optimum planted OVT(s) had the lowest total disease incidence. Overall average field performance for pod yields and dollar values were significantly highest in the optimum-planted tests with maximum-inputs including irrigation. Significant differences were also found among the 19 peanut cultivars. ‘Georgia-06G’, ‘Georgia-12Y’, and ‘Georgia-18RU’ had the lowest relative TSW incidence compared to the other runner-type cultivars. ‘Georgia-19HP’ had the lowest TSW incidence and total disease incidence among the virginia-type cultivars. Among the runner cultivars, Georgia-12Y had the lowest total disease incidence at the end of the season. The highest pod yields were found with Georgia-06G and ‘Georgia-16HO’; whereas, Georgia-18RU and Georgia-06G had the highest dollar values among the runner-type peanut cultivars. Georgia-19HP had the highest pod yield and dollar value among the virginia-type cultivars.

On-Farm Evaluation of Nozzle Types for Peanut Pest Management Using Commercial Sprayers

Growers have rapidly adopted auxin-resistant cotton and soybean technologies. In Georgia, growers who plant auxin-resistant cotton/soybean are required to utilize nozzles that produce larger (coarser) droplets when spraying auxin herbicides to minimize potential off-target movement of pesticides. Consequently, these nozzles are also used in peanut (an important rotational crop with cotton) since changing nozzles between crops is uncommon for growers. However, larger droplets can result in reduced spray coverage which may lead to less effective pest control. Therefore, seven on-farm trials were conducted in commercial peanut fields using commercial sprayers from 2018 to 2020 across four different locations in Georgia to compare the spray performance of air-induction (AI) nozzles that produce very coarse to ultra coarse droplets (VMD50 ≥ 404 microns) with non-AI (conventional flat fan) nozzles that produce medium to coarse droplets (403≥VMD50≥236 microns) for pest management in peanuts. For each trial, test treatments were implemented in large replicated strips where each strip represented a nozzle type. For nozzle comparison, XR and XRC represented non-AI nozzles while TADF, TDXL, TTI, and TTI60 represented the commonly used AI nozzles in these trials. Spray deposition data for each nozzle along with disease ratings, weed and insect control ratings were collected in all on-farm trials. Peanut yield was collected at harvest. Results indicated that the AI nozzles produced larger droplets than the non-AI nozzles in all nozzle tests; however, the spray coverage varied among the nozzle types. Nozzle type did not influence pest (weed, disease and insect) control, or peanut yield (p≤0.10) in any of the on-farm trials. These results suggested that peanut growers can utilize these coarser droplet nozzles for pest management in fields with low to average pest pressure during the season. Future research on nozzle evaluation needs to investigate the influence of droplet size, carrier volume, and pressure on coverage and canopy penetration.

Resistance to rust (Puccinia arachidis Speg.) identified in nascent allotetraploids cross-compatible with cultivated peanut (Arachis hypogaea L.)

Peanut rust, caused by Puccinia arachidis Speg., is a foliar disease that plagues peanut production along with early and late leaf spots, Passalora arachidicola (Hori) U. Braun and Nothopassalora personata (Berk. & M.A. Curtis) U. Braun, C. Nakash, Videira & Crous, respectively. Rust can cause up to 80% yield losses without control and is widespread in tropical countries but is also a sporadic problem in the United States. An integrative plant management strategy with rust resistant peanut cultivars is needed to decrease dependence on costly fungicides and increase yields for farmers who cannot afford or do not have access to fungicides. Only moderate levels of rust resistance have been found in cultivated peanut germplasm, but fortunately, high resistance to rust has been identified in wild Arachis species that can be introgressed into peanut cultivars. In this study, 16 diploid, wild Arachis species, five diploid, interspecific hybrids, 11 unique, allotetraploid interspecific hybrids, and two cultivated peanut controls were tested for resistance to rust. Resistance was evaluated in vitro by incubation time, susceptibility index (calculated based on the number of lesions of different diameters)/ leaf area, total number of lesions/ leaf area, and total number of sporulating lesions/ leaf area. All wild Arachis species tested were very highly resistant to rust, except for A. ipaënsis , the B-genome progenitor of cultivated peanut. Additionally, all interspecific hybrids and synthetic allotetraploids not produced with A. ipaënsis as a parent did not show symptoms for rust. Any of these nine synthetic allotetraploids, BatCor , BatDur 1, BatDur 2, BatSten 1, GregSten , MagCard , MagDio , MagDur , and ValSten 1 are recommended for progression to QTL mapping of rust resistance. These resistance QTLs can be pyramided into peanut cultivars to protect yields in the United States and to increase yields in tropical, developing countries for farmers that cannot afford, or do not have access to, costly fungicides.

Evaluation of Leaf Spot Resistance in Wild Arachis Species of Section Arachis

Wild diploid Arachis species are potential sources of resistance to early (ELS) and late (LLS) leaf spot diseases caused by Passalora arachidicola (syn. Cercospora arachidicola Hori), and Nothopassalora personata (syn. Cercosporidium personatum (Berk. & Curt.) Deighton), respectively. Within section Arachis, limited information is available on the extent of genetic variation for resistance to these fungal pathogens. A collection of 78 accessions representing 15 wild species of Arachis section Arachis from the U.S peanut germplasm collection was evaluated for resistance to leaf spots. Screening was conducted under field (natural inoculum) conditions in Dawson, Georgia, during 2017 and 2018. Accessions differed significantly (P < 0.01) for all three disease variables evaluated, which included final defoliation rating, ELS lesion counts, and LLS lesion counts. Relatively high levels of resistance were identified for both diseases, with LLS being the predominant pathogen during the two years of evaluation. This research documents new sources of resistance to leaf spot diseases selected from an environment with high inoculum pressure. The presence of ELS and LLS enabled the selection of resistant germplasm for further introgression and pre-breeding.

Peanut Response to Flumioxazin and S-Metolachlor Under High Moisture Conditions

The United States produced $1.28 billion worth of peanuts in 2019 of which Georgia produced 51% of the total production (USDA-NASS 2021). Peanut is susceptible to weed competition due to slow canopy establishment, prostrate growth habit, and wide critical period for weed control from 3 to 8 weeks after planting (Burke et al. 2007; Everman et al. 2008). Georgia-06G is the dominant peanut cultivar planted in the southeast and in 2020, 87% of the acres grown for certified peanut seed available for sale to growers was Georgia-06G (Anonymous, 2020a). Peanut is commonly in rotation with cotton in the region and therefore, similar weed issues between these systems persist. This includes Palmer amaranth ( Amaranthus palmeri S. Watson) which has been documented to be resistant to multiple herbicide modes of action making its control difficult (Heap 2021). To minimize yield loss from weeds, preemergence (PRE) herbicides are frequently used in peanut to inhibit weed germination and provide residual weed control (Grichar et al. 2001). In response to resistance issues, producers have continued to integrate PRE herbicides into their herbicide programs to minimize weed emergence.

Influence of Plant Population and Harvest Date on Peanut (Arachis hypogaea) Yield and Aflatoxin Contamination

Establishing the optimum plant population and harvesting at optimum pod maturity are important in maximizing yield of peanut ( Arachis hypogaea L.). The interaction of these two practices have not been documented in Malawi with respect to both yield and aflatoxin contamination in peanut. Research was conducted in Malawi at Mpatsanjoka farm in Salima district during the 2015-2016 and 2016-2017 growing cycles to determine interactions of plant population and harvest date on peanut yield and aflatoxin concentration in peanut at harvest with the cultivar CG7. Peanut was seeded in raised beds spaced 75-cm apart with three different planting patterns to establish three final plant populations. A single row planting pattern consisted of one row of peanut on each center with seed spaced 15-cm apart was used to plant seed at a density of 89,000 seed/ha (referred to as the low plant seeding rate). A twin row planting pattern included two rows of peanut spaced at 25 cm apart with 15 cm between seeds was used to plant seed at a density of 178,000 seed/ha (referred to as the medium plant population). A triple row planting pattern consisted of three rows of peanut spaced 25 cm apart with 7 cm between seeds was used to plant seed at a density of 278,000 seed/ha (referred to as the high density). Peanut for seeding density was dug 10 days before physiological maturity of pods, at physiological maturity, and at 4 and 6 weeks after physiological maturity. Pod yield increased as seeding rate and subsequent plant population increased but decreased as harvesting was delayed past physiological maturity. Yield of peanut with the highest plant population exceeded that of low and medium populations; yield of the medium plant population was greater that the low population in one of two years. Aflatoxin concentration at harvest was not affected by plant population but increased as harvest was delayed past physiological maturity. Harvesting peanut 10 d prior to physiological maturity did not affect grain yield or aflatoxin contamination compared with harvesting at optimum maturity.

Response of peanut (Arachis hypogaea L.) genotypes to smut (Thecaphora frezii) in the peanut growing region of Argentina

Genetic resistance is the most efficient tool in crop disease management. Peanut smut is currently one of most important peanut diseases, with its incidence increasing in terms of both damage level and crop area covered. The aim of this study was to assess the response of different genotypes obtained by the Facultad de Agronomía y Veterinaria of the Universidad Nacional de Río Cuarto (Argentina) to smut and their yield. During the 2016/17, 2017/18 and 2018/19 crop seasons, three experimental assays were conducted in General Deheza (Córdoba province, Argentina) to evaluate the varieties Uchaima, Utré and Mapu, the advanced lines LAx-1, LAx-2, LAx-3 and LAx-4, and the cultivar Granoleico, which was used as susceptible control. Final incidence and severity of peanut smut, as well as kernel yield, were evaluated. The variety Utré and the advanced line LAx-1 exhibited the best response to smut over the three crop seasons, without differences between them, but differing significantly from the remaining genotypes. Both genotypes showed incidence below 6.8% and severity below 0.21. In the 2016/17 crop season, LAx-1 had the highest kernel yield (3791.6 kg/ha). In the 2017/18 and 2018/19 crop seasons, Utré had the highest yield (1065 and 3975 kg/ha). Kernel yield of susceptible genotypes was below 2851.6 kg/ha in the 2016/17 and 2018/19 crop seasons, and below 805 kg/ha in the 2017/18 crop season. Genotypes LAx1 and Utré are resistant to peanut smut. This is the first report of a peanut commercial variety developed in Argentina (Utré) with confirmed tolerance to smut.

Yield and Economic Response of Peanut (Arachis hypogaea L.) Cultivars to Prohexadione Calcium in Large-Plot Trials in Georgia

Prohexadione calcium, a plant growth regulator, has been used on virginia market type peanut cultivars for many years to manage excessive vine growth and improve digging efficiency. Prohexadione calcium has not been widely used on runner market type cultivars due to their slower growth habit and sporadic yield response at the labeled rate until recent research showed lower use rates of prohexadione calcium provided similar vine control and enhanced yield response. Large plot experiments were conducted in Colquitt county at the Darrell Williams Research Farm on the Sun Belt Ag Expo to quantify yield and market grade quality and economics of using prohexadione calcium at 105 g a.i./ha on six runner type cultivars. Prohexadione calcium was applied twice during the growing season. The first application was made when 50% or greater of lateral vines from adjacent rows were touching. A second application of each treatment was applied 14d after the first application. The runner type cultivars were Georgia-06G, Georgia-12Y, Georgia-13M, Georgia-14N, TUFRunner TM -297, and TUFRunner TM -511. Similar large-plot experiments were conducted on farms in Baker and Early counties evaluating yield and economic response of prohexadione calcium on Georgia-06G. A non-treated control was used in all experiments. Prohexadione calcium increased pod yield in all experiments ranging from 450 to 650 kg/ha compared to the non-treated control with response similar across cultivars. Prohexadione calcium reduced the dollar value per metric ton (DVMT) as a result of lowering total sound mature kernel (%TSMK) percentages up to 3 points. The higher yields obtained for the prohexadione calcium-treated peanut provided higher gross dollar value return/ha (GDR) in all experiments and higher gross dollar value return/ha above treatment cost (GDRAT) in the on-farm trials. Therefore, prohexadione calcium at 105 g/ha applied twice on runner market type peanut is warranted to improve yield and financial return when excessive vine growth is a concern.

A Note on a Greenhouse Evaluation of Wild Arachis Species for Resistance to Athelia rolfsii

Athelia rolfsii (Curzi) C.C. Tu & Kimbr. is the one of the most damaging pathogens of cultivated peanut, causing the soilborne disease known regionally as white mold, stem rot, or southern blight. Because the genetic base for cultivated peanut is narrow, wild Arachis species may possess novel sources of disease resistance. We evaluated 18 accessions representing 15 Arachis species ( batizocoi , benensis , cardenasii , correntina , cruziana , diogoi , duranensis , herzogii , hoehnei , kempff - mercadoi , kuhlmannii , microsperma , monticola , simpsonii , williamsii ) in the greenhouse for resistance to At. rolfsii . Assays were conducted on intact plants propagated from rooted cuttings inoculated with mycelial plugs, and lesion length and mycelial growth were measured at 4, 6, 10, and 12 days after inoculation. For lesion length, Arachis batizocoi (PI 468326 and PI 468327), and A. kuhlmannii PI 468159 were the most susceptible entries with a mean lesion length >50 mm at 12 days after inoculation. Arachis microsperma (PI 666096 and PI 674407) and A. diogoi PI 468354 had the shortest lesions with mean lengths ≤16 mm at 12 days after inoculation. Arachis cruziana PI 476003 and the two A. batizocoi PIs had the highest mean area under the disease progress curves (AUDPCs), and the lowest AUDPC was obtained from the A. microsperma PI 674407. Mycelial growth was correlated with lesion length in most species except A. monticola PI 497260 . These results may be useful to peanut geneticists seeking additional sources of resistance to Athelia rolfsii .