Richard L. Hassell

Genetic diversity among Lagenaria siceraria accessions containing resistance to root-knot nematodes, whiteflies, ZYMV or powdery mildew.

In recent years, there has been an increased interest in Europe and in the USA in grafting watermelon onto bottle gourd, Lagenaria siceraria (Mol.) Standl. In this study, genetic diversity and relationships were examined [using 236 sequence-related amplified polymorphism markers] among 56 United States plant introductions (PIs) of L. siceraria and PIs of important cucurbit crops [including Cucurbita maxima Duchesne (winter squash), Cucurbita pepo L. (squash and pumpkin), Citrullus spp. (watermelon), Cucumis melo L. (melon) and Cucumis sativus L. (cucumber)]. The analysis showed that L. siceraria is distinct and has similar genetic distances to the cucurbit species examined herein. The L. siceraria PIs were assembled into two major clusters. One cluster includes groups of PIs collected mostly in South Asia (India) and a few PIs collected in the Mediterranean region and in Northeast Africa. The second cluster includes groups of PIs collected mainly in Southern Africa and in North, Central and South America, and PIs collected in China, Indonesia and Cyprus. All L. siceraria PIs in this study were susceptible to the southern root-knot nematode (RKN) [ Meloidogyne incognita (Kofoid and White) Sandground]. However, several PIs, among them a group of closely related PIs collected in Mexico and Florida, were less infected with southern RKNs. All L. siceraria PIs were infested with whiteflies [ Bemisia tabaci (Gennadius)], while several PIs were less infested than others and need further evaluation and selection for developing breeding lines that may be less appealing to this pest. Most of the PIs that showed resistance to zucchini yellow mosaic virus and tolerance to powdery mildew were collected in India and belong to the same phylogenetic groups (PGs). Experiments with L. siceraria PIs representing different PGs showed similar grafting compatibility with watermelon. Findings from this study should be useful for the development of superior L. siceraria rootstock lines with enhanced resistance to diseases and insect pests of cucurbit crops.

Bemisia argentifolii (Homoptera: Aleyrodidae) Attacking Species of Medicinal Herbal Plants

Abstract Research was conducted on the production potential of selected medicinal herbal plant species as new crops suitable for cultivation in South Carolina. Whiteflies (Bemisia argentifolii Bellows & Perring) were found in an experimental production field infesting five perennial species of medicinal herbal plants [feverfew, Tanacetum parthenium (L.) Schultz-Bipontinus; St. John’s wort, Hypericum perforatum L.; purple coneflower, Echinacea pallida (Nuttall) Nuttall and E. purpurea (L.) Moench; and common valerian, Valeriana officinalis L.]. This article reports on whiteflies attacking and developing on these plant species. Density of whitefly nymphs was highest (mean = 2.3/cm2) on the second fully expanded leaf on the apical meristem of E. purpurea as compared with the same leaf position on the other plant species where average whitefly density ranged from 0.1 to 0.6 nymphs per square centimeter from late November 1998 through January 1999. Similarly, adult capture on sticky cards was high (mean = 123 whiteflies per card) in plots of E. purpurea compared with plots of the other four species (mean = 8 to 20 whiteflies per card per species), and adult counts were elevated in the highest (440 kg N/ha) of three fertility rates in E. purpurea. Moreover, laboratory tests agreed with the observation of a higher population of B. argentifolii on E. purpurea compared with the other four plant species. The whitefly completed development on all five plant species, and whitefly-associated parasitoids emerged from field-leaf samples of each plant species.

Supplemental Control of Lepidopterous Pests on Bt Transgenic Sweet Corn with Biologically-Based Spray Treatments

Abstract Biologically-based spray treatments, including nucleopolyhedroviruses, neem, and spinosad, were evaluated as supplemental controls for the fall armyworm, Spodoptera frugiperda (J. E. Smith), and corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), on transgenic sweet corn, Zea mays (L.) (Poales: Poaceae), expressing a Cry1Ab toxin from Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) (Bt). Overall, transgenic corn supported lower densities of both pests than did nontransgenic corn. Control of the fall armyworm was improved in both whorl-stage and tassel-stage corn by the use of either a nucleopolyhedrovirus or neem, but the greatest improvement was seen with spinosad. Only spinosad consistently reduced damage to ears, which was caused by both pest species. In general, efficacy of the spray materials did not differ greatly between transgenic and nontransgenic corn.

Insect Populations on Bacillus thuringiensis Transgenic Sweet Corn

Insect populations and damage in three plantings (early, mid-, and late-season) of Bacillus thuringiensis (Bt) transgenic sweet corn were compared to a non-transgenic isoline at Charleston, SC, dur...

Development and Field Evaluation of Multiple Virus-Resistant Bottle Gourd (Lagenaria siceraria)

In an effort to develop bottle gourd (Lagenaria siceraria) as a widely adapted rootstock for watermelon grafting, we sought to identify lines with broad resistance to several cucurbit viruses that are economically important in the United States. Preliminary analysis under greenhouse conditions indicated that the currently available commercial watermelon rootstocks were either highly susceptible or somewhat tolerant to one or more viruses. However, in greenhouse screening, several breeding lines of bottle gourd displayed broad-spectrum resistance to four viruses tested, including Zucchini yellow mosaic virus, Watermelon mosaic virus (WMV), Papaya ringspot virus watermelon strain (PRSV-W), and Squash vein yellowing virus. Resistance to PRSV-W and WMV was confirmed through field trials in two consecutive years at two different locations in South Carolina. Two breeding lines (USVL#1-8 and USVL#5-5) with broad-spectrum virus resistance could be useful materials for watermelon rootstock development.

NMR Spectroscopy Identifies Metabolites Translocated from Powdery Mildew Resistant Rootstocks to Susceptible Watermelon Scions

Powdery mildew (PM) disease causes significant loss in watermelon. Due to the unavailability of a commercial watermelon variety that is resistant to PM, grafting susceptible cultivars on wild resistant rootstocks is being explored as a short-term management strategy to combat this disease. Nuclear magnetic resonance-based metabolic profiles of susceptible and resistant rootstocks of watermelon and their corresponding susceptible scions (Mickey Lee) were compared to screen for potential metabolites related to PM resistance using multivariate principal component analysis. Significant score plot differences between the susceptible and resistant groups were revealed through Mahalanobis distance analysis. Significantly different spectral buckets and their corresponding metabolites (including choline, fumarate, 5-hydroxyindole-3-acetate, and melatonin) have been identified quantitatively using multivariate loading plots and verified by volcano plot analyses. The data suggest that these metabolites were translocated from the powdery mildew resistant rootstocks to their corresponding powdery mildew susceptible scions and can be related to PM disease resistance.

Revival of Herbalism and Its Roots in Medicine

ABSTRACT The proper use of phytomedicines in human health care may add a dimension currently lacking in the United States in the treatment of certain diseases and syndromes. Sales of botanicals have been rising for the past few years and are expected to increase 12% to 16% annually for the next few years. As agriculturists, we are developing production techniques using good management practices to grow and process these new crops. However, a fundamental understanding of the genesis of this “new” industry is needed to appreciate the historic use of herbs and significance in society.

Dilemma of regulating dietary supplements.

ABSTRACT The manufacturing of herbal preparations or dietary supplements, has become a multibillion dollar industry in the United States. Presently, dietary supplements are not considered drugs by the government, but are classified as food supplements. The Dietary Supplement Health and Education Act of 1994 (DSHEA) has defined dietary supplements as a product intended to supplement the diet that contains one or more of a vitamin, mineral, an herb or other botanical, an amino acid or a dietary substance to supplement the diet by increasing the total dietary intake, or concentrates, metabolites, constituents, extracts or combinations of any ingredients described above. The main limitation of DSHEA is that it deals only with herbs as dietary supplements, i.e., as foods and not as drugs. A quandary still exists among: (1) the consumers who want to use these products safely; (2) the government that wishes to protect its citizens from potential hazards; and (3) the conventional medical community still questioning the safety and efficacy of these products. DSHEA does not appear to be the final verdict on herbal regulation, but just the first step in a long process of interpretation, evaluation, and decision-making required in the U.S. for regulation of any new class of such products. This paper reviews the current status facing the consumer, medical industry, and government in regards to herbal use.

Mapping Resistance to Alternaria cucumerina in Cucumis melo

Infection with Alternaria cucumerina causes Alternaria leaf blight (ALB), a disease characterized by lesion formation on leaves, leading to substantial yield and quality losses in Cucumis melo (melon). Although fungicides are effective against ALB, reduction in the frequency of application would be economically and environmentally beneficial. Resistant melon lines have been identified but the genetic basis of this resistance has not been determined. A saturated melon genetic map was constructed with markers developed through genotyping by sequencing of a recombinant inbred line population (F6 to F10; n = 82) derived from single-seed descent of a F2 population from a cross between the ALB-resistant parent MR-1 and the ALB-susceptible parent Ananas Yokneum. The population was evaluated for A. cucumerina resistance with an augmented block greenhouse study using inoculation with the wounded-leaf method. Multiple quantitative trait loci (QTL) mapping identified two QTL that explained 33.9% of variation in lesion area. Several candidate genes within range of these QTL were identified using the C. melo v3.5 genome. Markers linked to these QTL will be used to accelerate efforts to breed melon cultivars resistant to ALB.

The effect of grafting on nitrogen use in determinate field-grown tomatoes

ABSTRACTGrafting tomato (Solanum lycopersicum L.) onto disease resistant rootstocks has grown in use in North America over the past two decades. Rootstocks have traditionally been bred and used for...