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One hundred U.S. sweetpotato [Ipomoea batatus (L.) Lam.] plant introductions (PIs) and four control cultivars were screened for insect injury in 1993. Of the least injured by insects, 56 and 31 were tested again in 1994 and 1995, respectively. Among control cultivars, the most highly resistant was `Regal' (moderately resistant), followed by `Beauregard' (susceptible), `Centennial' (susceptible), and `Jewel' (susceptible). Stem and root injury by the sweetpotato weevil (SPW) [Cylas formicarius elegantulus (Summers)] and root injury by the wireworm (Conoderus sp.)–Diabrotica sp. (cucumber beetle)– Systena sp. (flea beetle) (WDS) complex were measured. SPW stem injury was less severe (P ≤ 0.05) in 1994 and 1995 in PIs 508523, 531116, and 564107 than in control cultivars. PIs 508523 and 531116 also suffered less SPW root injury than did `Regal'. In the six PIs with least SPW root injury, PIs 538354, 564149, 508523, 538286, 531116, and 564103, 70% to 85% of the roots were not injured compared with 36% in `Regal' and 6% in `Jewel'. SPW root injury scores (0 = no injury; 5 = severe injury) in those PIs averaged 0.5 vs. 2.3 for `Regal'. Only in PI 538286 was WDS injury to roots less than in `Regal' over 2 years. However, eight additional accessions suffered less WDS injury than `Regal' in 1995 and four of those were among the six with least SPW injury. The lower levels of combined insect injury found in these four PIs (compared to `Regal') show that PIs have potential use for increasing insect resistance in sweetpotato improvement programs.

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Abstract

Resistance to Sphaerotheca fuliginea (Schlecht) Poll, was not found in 292 plant introductions of Cucurbita pepo L. Cucurbita moschata Duch. ex Poir, PI 179925 and PI 201254, were resistant Most plant introductions of Cucurbita maxima were resistant

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in wild relatives of the cultivated watermelon. In this article, we present results of greenhouse and field evaluation of the watermelon core collection of U.S. plant introductions (PIs) for resistance to SqVYV. Parts of this study have been

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One hundred plant introductions (PIs) were evaluated for sweetpotato-weevil resistance in experiment station field trials for 2 years in Beaumont, Miss. Weevil infestation was accomplished by applying adult weevils in year 1 and weevil infested roots in year 2. The percentage of uninjured roots ranged from 38% in `Centennial', the susceptible control, to 93% in PI538288. Severity of root and stem injury were measured in year 2. Stem injury ratings on a scale of 0, for no injury, to 4, for severe injury, ranged from 1.2 in PI564113 to 3.7 in `Beauregard'. Root injury ratings on a scale of 0 to 5 ranged from 0.1 in PI538288 to 4.2 in `Beauregard' (susceptible control). Thirty-five PIs had lower root injury values than `Regal' (resistant control), and the percentage of uninjured roots was higher in 45 PIs than in `Regal'. These results suggest that genes are available in PIs for increased levels of weevil resistance in sweetpotato.

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because incidence of pests and diseases of cowpea at this site are minimal because of the absence of large plantings of this or related crops. Genetic diversity for tolerance to alkaline soil conditions, such as those encountered at St. Croix, has been

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Plant Development Services, Inc. (PDSI), was organized in 1996 for the purpose of research, development and the marketing of new innovative landscape plants. PDSI focuses on discovery, evaluation and production of new clones that are superior in horticultural qualities to current ones in our industry. Some superior horticultural traits that PDSI looks for are disease and insect resistance, heat and cold tolerance, superior foliage, form, or flower, ease of propagation and cultivation, and marketability. All new ornamental plant introductions orginate from small producers, private breeders, or from our own research. PDSI offers new plant discoveries a place and method of evaluation, legal protection services, production and marketing. Our method of evaluation includes propagation and cultivation and can take varying lengths of time to complete. On an average, it can take 3 to 5 years of evaluation before final selections are made. Once we have a high confidence level on a particular variety we enter them into university trials. We also offer public gardens these new plants for public exposure and evaluation. This has given us valuable feedback on the performance of these new cultivars in different areas of the country. This exposure has also turned into promotion. As people notice these new plants established and performing well in landscapes, they become confident to try the plants on their own, often talking about them and sometimes writing about them. If a plant is patented, the patent belongs to the breeder and typically PDSI is the managing partner making decisions on royalties, promotion, production, and licensing. Royalties fund our program and are paid on a per plant basis, not per size.

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Abstract

Of 260 plant introductions (PI) of okra [Abelmoschus esculentus (L.) Moench.] evaluated for disease resistance, 39 were resistant to southern root knot nematode [Meloidogyne incognita (Kofoid & White) (Chitwood)], 9 were resistant to fusarium wilt caused by Fusarium oxysporum f. sp. vasinfectum (A & K) Snyder and Hansen, and 3 were resistant to both. An introduction of A. manihot L., a wild relative of okra, was highly resistant to fusarium wilt.

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Two hundred sixty-six Citrullus lanatus (Thumb.) Matsum. & Nakai accessions (Plant Introductions and named cultivars) were tested against a race 2 Sphaerotheca fuliginea (Schlechtend.: Fr.) Pollacci isolate to evaluate for resistance to powdery mildew disease. Growth room-grown seedlings were artificially inoculated with conidia from watermelon host leaves at 2-day intervals from the appearance of the first true leaf until test results data were taken, when the second true leaf was fully expanded. Plants were evaluated on a 1 to 9 scale of increasing disease severity. Disease indices (DIs) were calculated as weighted averages for each entry. All genotypes with resistant plants (powdery mildew rating 1 to 3) were reevaluated in a replicated test of 3 replications of 10 plants each. Disease indices were again calculated. Twenty-two plant introductions (PIs) and one named variety displayed intermediate resistance to powdery mildew in the replicated test with DIs ranging from 5.0 to 6.0.

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Abstract

Plant Introduction (PI) accessions of spinach (Spinacia oleracea L.) were evaluated for curly top resistance in greenhouse tests at Pullman and in field tests in the Columbia Basin near Basin City, Washington. In greenhouse tests of 185 accessions, possible resistance was observed in 4 that produced single symptomless plants, in 3 that survived long enough to produce some nonviable seed, and in 56 that produced dwarf green plants in which symptom expression and death were delayed. Of the 178 accessions observed in the field, 13 produced 1 symptomless pistillate plant each, 1 produced a single tolerant pistillate plant, and 1 produced 11 symptomless pistillate plants.

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Woody plant improvement research has been an active program at North Dakota State Univ. (NDSU) for many years. Eighteen cultivars have been introduced since 1986, and ≈10 additional releases are anticipated over the next 6 years. These superior, winterhardy cultivars have increased the inventory of adapted woody plants for landscape use in the northern plains, particularly USDA hardiness zones 3 and 4. Emphasis will be placed on recent introductions and promising plants for potential future release. An extensive, statewide cooperative evaluation program is conducted at seven sites throughout North Dakota and also at the NDSU Research Arboretum near Absaraka.

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