D. Michael Jackson

Effects of cuticular duvane diterpenes from green tobacco leaves on tobacco budworm (Lepidoptera: Noctuidae) oviposition

Five cuticular chemical components isolated from the green leaves of tobacco introductions (TIs) and a commercial tobacco cultivar were tested for their effects on tobacco budworm,Heliothis virescens (F), oviposition in cage bioassays, and field experiments. These chemicals were sprayed onto budworm-resistant TI 1112 tobacco which produces low levels of most cuticular components. Individual duvane diterpenes (α- and β-4,8,13-duvatrien-1-ols and α- and β-4,8,13-duvatriene-1,3-diols) increased tobacco budworm egg laying on sprayed TI 1112 plants.cis-Abienol, docosanol, and docosanyl myristate were inactive.

Ovipositional response of tobacco budworm moths (Lepidoptera: Noctuidae) to cuticular labdanes and sucrose esters from the green leaves ofNicotiana glutinosa L. (Solanaceae)

Field plots of three accessions ofNicotiana glutinosa L. (Nicotiana species accessions 24, 24A, and 24B) at Oxford, North Carolina and Tifton, Georgia were heavily damaged by natural populations of tobacco budworms,Heliothis virescens (F.), during 1985–1989. Experiments in outdoor screen cages demonstrated that all accessions ofN. glutinosa were as prone to oviposition byH. virescens moths as was NC 2326, a commercial cultivar of flue-cured tobacco,N. tabacum L. However, in greenhouse experiments, tobacco budworm larvae did not survive or grow as well when placed on plants ofN. glutinosa as they did when placed on plants of NC 2326. Four labdane diterpenes (manool, 2-hydroxymanool, a mixture of sclareols, and labda-13-ene-8α,15-diol [labdenediol]) and two sucrose ester fractions (2,3,4-tri-O-acyl-3′-O-acetyl-sucrose [G-SE-I] and 2,3,4,-tri-O-acyl-sucrose [G-SE-II]) were isolated from green leaves of the three accessions ofN. glutinosa. These components were bioassayed for their effects on the ovipositional behavior of tobacco budworm moths using small screen cages in a greenhouse at Oxford, North Carolina. Labdenediol, manool, and both sucrose ester fractions stimulated tobacco budworm moths to oviposit on a tobacco budworm-resistant Tobacco Introduction, TI 1112 (PI 124166), when these materials were sprayed onto a leaf.

Comparison of the Volatile Flower Oils of Nicotiana rustica and N. forgetiana

ABSTRACT The volatile constituents obtained by vacuum-steam distillation of the flowers of Nicotiana rustica and of N. forgetiana were profiled by capillary GC and characterized by GC/MS. Compounds comprising 74% of N. rustica flower oil and 72% of N. forgetiana flower oil were identified. Seventeen compounds were observed in N. rustica oil, with the alkaloid, nicotine (25.92%), and the sesquiterpene, aromadendrene (11.26%) being the major constituents. Of the 14 compounds observed in N. forgetiana oil, no constituents exceeded 10% of the total amount. Farnesyl acetone (4.97%), β-pinene (4.19%), acoradiene (3.81%) and (Z)-3-hexenyl acetate (3.97%) were present in highest concentrations. Twelve compounds were common to the oils of both species, although seven of these were aliphatic C21-C25 hydrocarbons. These hydrocarbons occurred in significantly greater amounts in N. forgetiana. (Z)-3-Hexenol was die only component found at a level exceeding 5% in both species.

Volatile Constituents from the Flowers of Nicotiana longiflora

ABSTRACT The volatile constituents obtained by vacuum-steam distillation of flowers of Nicotiana longiflora were characterized by capillary GC and GC/MS. Twenty-nine compounds, comprising 75% of the GC profile of volatiles, were identified. The three major constituents were the labdane alcohol, manool; the acyclic diterpene, neophytadiene; and 2,4-diphenyl-4-methyl-2(Z)pentene. The volatile concentrate exhibited an aroma characteristic of green bell peppers, attributable to the presence of minor amounts of the potent aroma compound, 2-methoxy-3-isobutylpyrazine, previously unreported in Nicotiana species.

Insect Resistance in Traditional and Heirloom Sweetpotato Varieties

ABSTRACT Fifty-nine sweetpotato cultivars, including 16 heirlooms, 11 near-heirlooms (developed in the 1960s and 1970s), 19 cultivars from the 1980s, and 13 modern varieties (since 1990), were evaluated for resistance to soil insects in field experiments during 2010–2011 at the U.S. Department of Agriculture-Agriculture Research Service, U.S. Vegetable Laboratory (USDA-ARS, USVL), Charleston, SC. These experiments included two insect-susceptible control cultivars (‘Beauregard’ and ‘SC1149-19’) and four insect-resistant control cultivars (‘Charleston Scarlet,’ ‘Regal,’ ‘Ruddy,’ and ‘Sumor’) that were developed by the USDA-ARS, USVL sweetpotato breeding program. Sweetpotato genotypes differed significantly in resistance measured by the overall percentage of injured roots, WDS ( Wireworm, Diabrotica, and Systena) index, the percentage of roots damaged by the sweetpotato weevil (Cylas formicarius F.), the percentage of roots damaged by the sweetpotato flea beetle (Chaetocnema confinis Crotch), and the percentage of roots damaged by white grub larvae (including Plectris aliena Chapin and Phyllophaga spp.). Twenty-three sweetpotato cultivars had a lower percentage of injured roots than the susceptible control genotype, SC1149-19, while 14 varieties had a lower percentage of injured roots than Beauregard, one of the leading commercial orange-fleshed cultivars in the United States. Over the 2-yr period, Ruddy (7.6%) had the lowest percentage of injured roots and ‘Carolina Ruby’ (84.6%) the highest percentage of injured roots. Carolina Ruby (1.07) also had the highest WDS index, but 15 genotypes had a significantly lower WDS index than either susceptible control, SC1149-19 (1.03) or Beauregard (0.82). Ruddy (0.07) and ‘Murasaki-29’ (0.09) had the lowest WDS indices. Forty-five genotypes had a significantly lower percentage infestation by flea beetles than SC1149-19 (12.3%), and the highest level of flea beetle infestation was for ‘Bonita’ (18.9%). The highest percent white grub infestation was for ‘Caromex’ (19.6%), however none of the genotypes had significantly less white grubs than the susceptible controls. The highest infestation of sweetpotato weevils was observed for SC1149-19 (17.9%), while 29 genotypes had significantly lower percentage of sweetpotato weevil infestation than SC1149-19. The moderate to high levels of resistance to soil insect pests exhibited by many of these traditional and heirloom cultivars may provide useful sources of germplasm for sweetpotato breeding programs.

Effects of Cucurbitacin on the Activity of Nucleopolyhedroviruses Against Pickleworm Larvae2

Abstract The cucurbitacin-containing feeding stimulant (Invite® EC) was attractive to second instar pickleworm larvae in the absence of a food source. Second instar pickleworm larvae also fed preferentially on cucumber fruits that were treated with a 1% (0.01×) solution of Invite EC compared with untreated fruit. However, 1% Invite did not stimulate feeding on artificial diet, squash leaves, or squash fruits. Concentrations of Invite as low as 0.001% were effective in increasing the efficacy of the velvetbean caterpillar, Anticarsia gemmatalis Hübner, multiply-embedded nucleopolyhedrovirus (AgMNPV) against second instar pickleworms. A 1% Invite solution also increased the efficacy of the celery looper, Anagrapha falcifera (Kirby), multiply-embedded NPV (AnfaMNPV) against second instar pickleworms.

Genetic Diversity and Population Structure of the USDA Sweetpotato (Ipomoea batatas) Germplasm Collections Using GBSpoly

Sweetpotato (Ipomoea batatas) plays a critical role in food security and is the most important root crop worldwide following potatoes and cassava. In the United States (US), it is valued at over

Identification of a pheromone blend attractive to Manduca sexta (L.) males in a wind tunnel

700 million USD. There are two sweetpotato germplasm collections (Plant Genetic Resources Conservation Unit and US Vegetable Laboratory) maintained by the USDA, ARS for sweetpotato crop improvement. To date, no genome-wide assessment of genetic diversity within these collections has been reported in the published literature. In our study, population structure and genetic diversity of 417 USDA sweetpotato accessions originating from 8 broad geographical regions (Africa, Australia, Caribbean, Central America, Far East, North America, Pacific Islands, and South America) were determined using single nucleotide polymorphisms (SNPs) identified with a genotyping-by-sequencing (GBS) protocol, GBSpoly, optimized for highly heterozygous and polyploid species. Population structure using Bayesian clustering analyses (STRUCTURE) with 32,784 segregating SNPs grouped the accessions into four genetic groups and indicated a high degree of mixed ancestry. A neighbor-joining cladogram and principal components analysis based on a pairwise genetic distance matrix of the accessions supported the population structure analysis. Pairwise FST values between broad geographical regions based on the origin of accessions ranged from 0.017 (Far East – Pacific Islands) to 0.110 (Australia – South America) and supported the clustering of accessions based on genetic distance. The markers developed for use with this collection of accessions provide an important genomic resource for the sweetpotato community, and contribute to our understanding of the genetic diversity present within the US sweetpotato collection and the species.