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W. Patrick Wechter, Amnon Levi, Kai-Shu Ling, Chandrasekar Kousik and Charles C. Block

plates and grown for an additional 24 h for use in the described assays. Table 1. Acidovorax avenae subsp. citrulli isolates used for study. Plant material. Seeds of PIs were obtained from the USDA, ARS, North Central Regional Plant Introduction

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W. Patrick Wechter, Mark W. Farnham, J. Powell Smith and Anthony P. Keinath

resistance that might be incorporated into improved cultivars of these species. Materials and Methods Plant materials. B. juncea and B. rapa accessions (Plant Introductions) were obtained from the USDA, ARS, North Central Regional Plant

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Joseph N. Wolukau, Xiao-Hui Zhou, Ying Li, Yong-Bin Zhang and Jin-Feng Chen

in plant introduction 140471 to be near immunity. On the contrary, McGrath et al. (1993) contends no sufficient resistance to GSB is available in melon. Furthermore, resistance in plant introduction 140471 has recently been described as variable

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Chandrasekar S. Kousik, Amnon Levi, Kai-Shu Ling and W. Patrick Wechter

of plant introductions (PI) of bottle gourd ( Lagenaria siceraria ) for resistance to powdery mildew caused by Podosphaera xanthii z . Fig. 1. Frequency of distribution of the original screening of 234 bottle gourd ( Lagenaria

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Paul G. Thompson, John C. Schneider, Boyett Graves and R. Crofton Sloan Jr.

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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Chandrasekar S. Kousik, Scott Adkins, William W. Turechek and Pamela D. Roberts

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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Paul G. Thompson, John C. Schneider and Boyett Graves

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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Larry A. Rupp, Richard M. Anderson, James Klett, Stephen L. Love, Jerry Goodspeed and JayDee Gunnell

our industry partner, Native Roots, LLC, makes this feasible as demand for water-conserving native plants grows. Colorado model Plant Select is a very successful plant introduction and promotion program for the Rocky Mountain and plains states. It was

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Claude E. Thomas, Amnon Levi and Ellis Caniglia

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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Michael A. Creller and Dennis J. Werner

Surface morphology of peach [Prunus persica (L.) Batsch] Plant Introduction 133984 (`Marina') differs from standard peach and nectarine clones. Scanning electron microscopic examination of `Marina', a standard peach (`Contender'), and a nectarine (`Sunglo') was conducted. At anthesis, `Marina' ovaries were glabrous, similar to `sunglo' nectarine. Fruit of `Contender' were fully pubescent at anthesis. Examination of `Marina' fruit two weeks after anthesis revealed the presence of both pubescent and glabrous sectors on the fruit surface. At fruit maturity, most of the fruit surface of `Marina' was covered with pubescence, but trichome density was considerably less than `Contender' peach. Trichome morphology of `Marina' differed from that of `Contender'.