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Arthur Villordon, Christopher Clark, Tara Smith, Don Ferrin, and Don LaBonte

Forward and stepwise regression methods identified variables related to the influence of transplanting date on yield of U.S. #1 sweetpotatoes. The variables were mean minimum soil temperature 5 days after transplanting (DAT), wind direction at transplanting, and accumulated heat units (growing degree-days) 5 DAT. Machine learning techniques identified the same variables using leave-one-out and k-fold cross-validation methods. Growers and crop consultants, in collaboration with knowledge workers, can use this information in conjunction with public and subscription-based weather forecasts to further optimize transplanting date determination and for making risk-averse decisions. These results help to underscore the importance of consistent transplant establishment as one of the determinants of storage root yield in sweetpotatoes.

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Ramón A. Arancibia, Cody D. Smith, Don R. LaBonte, Jeffrey L. Main, Tara P. Smith, and Arthur Q. Villordon

Consumption of sweetpotato (Ipomoea batatas) has increased in the past decade in part because of its nutritional and health attributes, and because of the availability and convenience of processed products. The sweetpotato processing industry is expanding and supplying more sweetpotato products than ever before. Unlike the medium-sized roots (U.S. no.1) preferred for fresh market, large (jumbo) roots is accepted and in certain cases desired by the processing industry, and overall yield is preferred over strict sizing requirements and aesthetic appeal. Therefore, this study investigated the yield increase and grade proportions in response to plant spacing and extension of the growing period to improve profitability of the production system. Experiments with ‘Beauregard’ and ‘Evangeline’ sweetpotato were conducted in Mississippi and Louisiana during 2010 and 2011. Treatments consisted of a combination of early and late planting date and delay in harvest, in-row plant spacing, and row width. Yield increase was inconsistent with delaying harvest and appears to depend on environmental conditions at harvest late in the season. Marketable yield was consistently greater in early plantings than late plantings. Yield of U.S. no.1 grade was unaffected by delaying harvest regardless of planting date. Delaying harvest in early plantings contributed to increase jumbo-sized roots and marketable yield. The economic assessment of delaying harvest in early plantings indicated a gain in net benefit either when hand harvested for fresh market or field run bulk harvested for processing. Row width and in-row plant spacing had only a marginal effect on yield of canner grade (small-sized roots). The economic assessment of changing plant density indicated no gain in net benefit, which indicates that choice of plant density can depend on other factors.

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A. Shiferaw, M.W. Smith, R.D. Eikenbary, and Don C. Arnold

Perennial legumes ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Ground covers were `Kenland' red clover (Trifolium pratense), `Louisiana S-1' white clover (Trifolium repens), a mixture of these two legumes, or bermuda grass (Cynodon dactylon), each in 5 ha plots. Nitrogen was applied at 0-200 kg·ha-1 N in 50 kg intervals to bermuda grass plots, and was omitted on the legumes. Aphids feeding on the legumes attracted lady beetles; however, lady beetle populations in the tree canopies were not affected by ground cover treatment. The most abundant lady beetle species in legumes were Coleomegilla maculata lengi (77%) and Coccinella septempunctata (13%); whereas, dominant species in tree canopies were Coleomegilla maculata lengi (33%). Olla v-nigrum (20%). Cycloneda munda (18%) and Coccinella septempunctata (15%). Several other beneficial arthropods were sampled in legumes and tree canopies. Aphid populations feeding on pecans were low (peak population ≈ 2 aphids/leaf), and not affected by ground cover treatment. Legumes supplied the equivalent of applying 68-156 kg·ha-1 N.

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A. Shiferaw, M.W. Smith, R.D. Eikenbary, and Don C. Arnold

Perennial legume ground covers were evaluated to supply N and increase beneficial arthropod densities in pecan orchards. Treatments were pure stands and a mixture of `Kenland' red clover (Trifolium pratense L.) and `Louisiana S-l' white clover (Trifolium repense L.). The control plot was a grass sod. Nitrogen was applied at 0 to 200 kg·ha–1 in 50-kg intervals to the trees in the grass plots, but no N was applied to the legume plots. Aphids and beneficial arthropods were monitored in legumes and pecan canopies. Beneficial arthropods monitored were Coccinellidae, Chrysopidae, Nabis, Syrphid, and spiders. The most abundant beneficial arthropods were spiders, Coccinellidae, Chrysopidae, and Nabis respectively. In pecan canopies, spiders, Coccinellidae, Chrysopidae were the most abundant. The legumes supplied ≤156 kg N/ha to the pecan trees.

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Victor M. Guerrero-Prieto, Mirna Carrasco, Alberto Rodriguez, and Don W. Smith

Red Delicious apple is the second most important cultivar grown in the State of Chihuahua, Mexico. Red Delicious apple is well known for pollination problems which can reduce yield. Previous research suggested female sterility might account for irregular fruit set in the apple growing region of Chihuahua. Pollen tube growth and ovule longevity were examined in 1990 under field conditions in Chihuahua. Fluorescent light with Aniline Blue dye was used to determine pollen tube growth and ovule viability. Five days after pollination, 86% of the styles sampled had pollen tubes through the entire style and only 1% of the ovules were non-viable. These results do not support female sterility as the cause of irregular fruit set. Future research might be directed to the question of pollen viability on the stigma.

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Don R. La Bonte, Christopher A. Clark, Tara P. Smith, Arthur Q. Villordon, and C. Scott Stoddard

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Don R. La Bonte, Christopher A. Clark, Tara P. Smith, Arthur Q. Villordon, and C. Scott Stoddard

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Don R. La Bonte, Christopher A. Clark, Tara P. Smith, and Arthur Q. Villordon

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Don R. La Bonte, Christopher A. Clark, Tara P. Smith, and Arthur Q. Villordon

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Barbara Gilmore, Nahla Bassil, April Nyberg, Brian Knaus, Don Smith, Danny L. Barney, and Kim Hummer

Peonies (Paeonia), the grand garden perennial of spring and early summer, are economically important to the international cut flower market. Herbaceous peonies (Paeonia section Paeonia), tree peonies (Paeonia section Moutan), and intersectional crosses between the two types (Itoh Paeonia hybrids) are of interest to gardeners, growers, and nursery producers. Thousands of peony cultivars exist and identity is traditionally determined by experienced horticulturists knowledgeable in plant and bloom characteristics. With DNA extraction possible during any time of the year, molecular markers can provide genotype identity confirmation for dormant roots or mature post-bloom plants. The primary objective of our research was to rapidly and inexpensively develop microsatellite markers in a range of Paeonia species using barcoded Illumina libraries. A secondary objective was to apply these simple sequence repeat (SSR) markers to fingerprint 93 accessions that include tree, intersectional, and herbaceous peonies. We used 21 primers to distinguish cultivars and their close relatives. Also from our sequence information, greater than 9000 primers were designed and are made available.