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Jeanine M. Davis and Jacqulyn T. Greenfield

Seventeen North Carolina farmers received $5000 grants to grow medicinal herbs as part of a research study to determine the economic feasibility of producing herbs in different regions of the state, including producing the quality and quantity of medicinal herbs required by the industry at a price that is competitive in a global market. With the help of five buyers in the natural products industry, four medicinal herbs were selected to be grown: California poppy, dandelion, Echinacea purpurea, and valerian. The growers experimented with new crops, learned new production methods, and adapted existing methods and equipment to these crops. These growers were also introduced to new markets and made connections with buyers, statewide and nationally, in an industry that can be difficult to enter. Growers were responsible for keeping detailed records of production, harvest, and postharvest handling. To produce a marketable crop in 1 year, some of the growers started seedlings in their greenhouses, while others direct seeded into the field. With the natural products industry moving toward a nonchemically grown product, growers in this project had to produce their crop without pesticides. Weed pressures were the biggest challenge to most of the growers. Prior to harvest, bioactive constituents were tested on the dried raw material to see if levels met buyers' requirements. Other testing methods determined percentage of ash, moisture content, microbial limits, and heavy metal accumulation. For postharvest handling, tobacco farmers who had drying facilities experimented with different temperature regimes to produce a uniformed dried material. Buyers and growers were then introduced to each other to complete the sale of goods.

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T.K. Hartz, P.R. Johnstone, E.M. Miyao, and R.M. Davis

Mustard (Brassica spp.) cover crop residue has been reported to have significant `biofumigant' action when incorporated into soil, potentially providing disease suppression and yield improvement for the succeeding crop. The effects of growing over-winter mustard cover crops preceding processing tomato (Lycopersicon escultentum Mill.) production were investigated in six field trials in the Sacramento Valley of California from 2002–04. A selection of mustard cover crops were compared to a legume cover crop mix, a fallow-bed treatment (the current grower practice in the region), and in two of the six trials, fumigation treatments using metam sodium. Mustard cover crops removed 115 to 350 kg·ha–1 N from the soil profile, reducing NO3-N leaching potential. Soil populations of Verticillium dahliae Kleb. and Fusarium spp. were unaffected by the cover crops, and there was no evidence of soilborne disease suppression on subsequent tomato crops. Mustard cover crops increased tomato yield in one field, and reduced yield in two fields. In one of two fields, metam sodium fumigation significantly increased tomato yield. We conclude that, while environmental benefits may be achieved, mustard cover cropping offers no immediate agronomic benefit for processing tomato production.

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P. R. Johnstone, T. K. Hartz, E. M. Miyao, and R. M. Davis

Mustard cover crop residue has been reported to have a “biofumigant” action when incorporated into the soil, potentially providing significant disease suppression and yield improvement for the succeeding crop. Such activity could be particularly useful in processing tomato rotations, where consecutive cropping invariably results in yield decline. Agronomic and environmental effects of growing over-winter mustard cover crops preceding tomato production were investigated in three field trials between 2002 and 2004. Two mustard cover crops [`Pacific Gold', a brown mustard (Brassica juncea), and `Caliente', a blend of brown and white mustard (Sinapis alba)] were compared to a legume cover crop mix, a fallow bed treatment (the standard grower practice in this region), and, in two of the three trials, a fumigation treatment using metam sodium. No suppression of soil populations of Verticillium dahliae or Fusarium spp. was observed with the mustard cover crops, nor was there any visual evidence of disease suppression on subsequent tomato crops. In these fields, the mustard either had no effect, or reduced tomato yield, when compared to the fallow treatment. At one of two sites, metam sodium fumigation significantly increased tomato yield. The presence of a cover crop, whether mustard or legume, reduced winter runoff by an average of 50% over two years of trials. No benefit of mustard cover cropping beyond this reduction in winter runoff was observed.

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Kelly J. Vining, Q Zhang, C.A. Smith, and T.M. Davis

Resistance gene analog (RGA) sequences were obtained from four Mentha longifolia (L.) Huds. accessions using degenerate polymerase chain reaction (PCR) primers targeting the conserved nucleotide binding site domain found in many plant disease resistance genes. Seven distinct RGA families were identified. All M. longifolia RGAs showed similarity to sequences of the non-toll-interleukin 1 receptor R gene class. In addition, degenerate PCR primers based on the tomato (Solanum lycopersicum L.) verticillium wilt resistance (Ve) genes were used to PCR-amplify a 445-base pair (bp) Ve-like sequence from M. longifolia that had ≈57% predicted amino acid identity with Ve. Mint-specific primers based on the original mint Ve sequence were used to obtain mint-specific Ve sequences from four M. longifolia accessions and from peppermint (Mentha ×piperita L.) cultivar ‘Black Mitcham’ that had 95% to 100% predicted amino acid identity to the original mint Ve sequence. Inverse PCR was then used to obtain flanking mint Ve sequence from one M. longifolia accession extending the mint Ve sequence to 1077 bp. This is the first report of RGA sequences in the Lamiaceae and the first report of Ve-like sequences obtained with degenerate PCR primers.

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Michael T. Martin Jr., Geoffrey M. Weaver, Matthew R. Chappell, and Jerry Davis

A study was conducted to observe changes in mineral element concentrations within different sections of leafy stem cuttings of Hibiscus acetosella ‘Panama Red’ (PP20121) during a 21-day propagation period under standard industry propagation conditions. Concentrations of 13 mineral elements were analyzed in leaves, lower stems (below substrate), upper stems (above substrate), and roots at 3-day intervals. Before root emergence (day 0–6), P, K, Zn, Ca, and Mg concentrations decreased in the shoots (including upper stems and leaves), whereas Zn, Ca, and B concentrations decreased in the lower stems. Sulfur increase occurred in lower stems before root emergence. After rooting (day 9–21), N, P, Zn, Fe, Cu, and Ni concentrations decreased in the roots; K, S, B, and Mg concentrations increased. In the lower stems, N, P, K, S, and Zn concentrations decreased, whereas B increased. Potassium concentration decreased in the leaves; P, K, S, and Zn decreased in the upper stems. Calcium and Mg increased in leaves. This study indicates specific nutrients are important in adventitious rooting, and that it is important to analyze rooting as a function of fine-scale temporal measurements and fine-scale sectional measurements.

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M.E. Kane, G.L. Davis, T.D. Hoffner, and R.J. Henny

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K.J. Vining, Q. Zhang, A.O. Tucker, C. Smith, and T.M. Davis

Mentha longifolia, a wild relative of the polyploid, cultivated Mentha (mint) species, was evaluated as a potential model system for genetic research relevant to the cultivated mints. Fourteen Mentha longifolia accessions maintained by the US Department of Agriculture (USDA), Agricultural Research Service, National Clonal Germplasm Repository (NCGR), were highly diverse with respect to geographic origin, oil composition, verticillium wilt resistance, aspects of morphology, and molecular marker polymorphism. Accession CMEN 584 was the only carvone chemotype, while CMEN 682 was the only accession with high menthol content. Trans-piperitone oxide was the primary oil component of accessions CMEN 17 and CMEN 18, while pulegone was most abundant in CMEN 20, CMEN 500, CMEN 501, and CMEN 585. Four accessions—CMEN 585, CMEN 17, CMEN 501, and CMEN 81—were consistently resistant to verticillium wilt, while CMEN 584 and CMEN 516 were highly susceptible. Pairwise similarity coefficients were calculated and a UPGMA (unweighted pair-group analysis) tree was constructed on the basis of 63 informative randomly amplified polymorphic DNA (RAPD) marker bands. CMEN 585 and CMEN 584 shared the greatest number of bands (16), and formed a distinct cluster in the UPGMA tree. Seven pairs of accessions had no bands in common, emphasizing the high degree of molecular diversity represented by these accessions. The favorable features of diploid (2n = 2x = 24) genome constitution, comparatively small genome size (400 to 500 Mb), self-fertility, fecundity, and diversity with respect to economically relevant traits, contribute to M. longifolia's potential usefulness as a model system for the cultivated mints. As a perennial species amenable to vegetative propagation, M. longifolia's spectrum of susceptibility/resistance to an important vascular wilt disease encourages its further evaluation as a system for broader studies of plant–microbe interactions and disease resistance mechanisms.

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K.M. Batal, M.R. Hall, D.M. Granberry, J.T. Garrett, D.R. Decoteau, R.T. Dufault, G.D. Hoyt, T.C. Gilsanz, J.M. Davis, and D.C. Sanders

A vegetable production system using winter cover crops and N rates was evaluated for several years in Georgia, South Carolina, and North Carolina. Snap bean, cucumber, tomato, potato, and sweetpotato crops were tested at different locations. Cover crop plots produced higher yields and better quality in all locations as seasons progressed over 4 years. Soil N levels in fallow, wheat, and clover plots were similar at initiation, but N gradually increased in clover plots in successive years. Yield and quality of root crops improved with Crimson clover without N applications compared to fallow plots with 60 kg N/ha. Effects on yield and tuber size are discussed. Nitrate and NH4-N in the soil profile from 15- to 150-cm depth were monitored at all locations. Nitrogen availability, depletion, and leaching below the root zone were determined. At low N rate, clover plots had slightly higher NO3 in the soil profile; however, at high N rate, N supply by clover was not as critical, and N leaching was detected at much lower depths than at low N rates.

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Wenjing Pang, John E. Luc, William T. Crow, Kevin E. Kenworthy, Robert McSorley, and Robin M. Giblin-Davis

Breeding and improvement of new bermudagrass (Cynodon spp.) cultivars with superior nematode tolerance are essential because sting nematode (Belonolaimus longicaudatus Rau) is a major limitation for use of bermudagrass in the sandy coastal soils of the southeastern United States. The screening of both African (Cynodon transvaalensis) and common (C. dactylon) bermudagrass is necessary to develop triploid hybrid cultivars. Five commercial cultivars and 46 germplasm accessions of bermudagrass were tested for nematode responses in two greenhouse trials in 2009. Turfgrass was grown in sand-filled plastic conetainers and inoculated with 50 sting nematodes per conetainer. Nematode and root samples were collected 90 d after nematode inoculation. Fifteen bermudagrass accessions did not have measurable root loss from inoculation with sting nematode. Seven bermudagrass accessions, including ‘Celebration’, produced longer roots in sting nematode-infested soil than the standard ‘Tifway’. Differences in final nematode numbers were identified among the genotypes, and different relative responses were identified in variable ploidy levels and origins. This could aid a turfgrass breeding program by elucidating the genetic diversity available for breeding future bermudagrass cultivars for golf course cultivation.

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K.M. Batal, D.R. Decoteau, J.T. Garrett, D.M. Granberry, D.C. Sanders, J.M. Davis, G.D. Hoyt, and R.J. Dufault

Cucumber and potato crops were tested in a rotation with winter cover crops at different locations in Georgia, North Carolina, and South Carolina from 1991 to 1994. Biomass DM of vegetable crops was greatest when grown after crimson clover. Clover plantings resulted in a greater biomass than wheat when preceded spring cucumber crop. Vegetable biomass produced on clover plots or with N rates of 60 to 120 kg·ha–l was equivalent. Nitrogen recovery by cover and vegetable crops was enhanced by clover plantings. Clover biomass (tops only) provided an average of 138 kg N/ha for the cucumber crop, compared to an average of 64 kg N/ha provided by wheat. Nitrogen recovery by vegetable crops was also enhanced with 60–120 kg N/ha rates. Yields were highest when high N rates were used and when crops were produced on clover plots. Vegetable yield, cover crop biomass, and N recovery were positively correlated with vegetable biomass and applied N.