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Juan C. Diaz-Perez, D. Bertrand, and D. Giddings

Tomato spotted wilt virus (TSWV) can cause serious damage to tomato, pepper, lettuce, and other crops. The virus is transmitted by several species of thrips. The objective of this study was to determine the effect of the time (t, days after transplanting) when TSWV symptoms first appeared on tomato plant size and fruit yield. Tomato (`Florida-47') plants were drip-irrigated and planted over black plastic mulch. The experiment was carried out in Tifton, Ga., during Spring 1999. High populations of thrips were detected since early stages of plant development, which resulted in a high incidence of TSWV. Plant fresh weight was significantly higher (r 2 = 0.632, n = 216) the later in plant development TSWV symptoms first appeared (i.e., with increasing t values). Total fruit production of individual plant linearly increased with increasing t values (r 2 = 0.664, n = 216). As with total fruit production, fruit marketable yield was also higher with increasing t values; however, marketable yield was significantly reduced even when plants were infected later in the season (t > 55 days after transplanting). Our results suggest that it is important to keep tomato plants free from TSWV as long as possible. This applies to both developing and developed plants.

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Scovia Adikini, Settumba B. Mukasa, Robert O.M. Mwanga, and Richard W. Gibson

symptom was made and disease incidence was recorded. The root sprouts were tested using nitrocellulose membrane (NCM)–enzyme-linked immunosorbent assay (ELISA) to detect and identify some of the viruses present in the roots. The symptomless root sprouts

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John F. Murphy and Fenny Dane

aphid activity, thereby increasing plant-to-plant spread of the virus ( Raccah, 1986 ). Cultural practices, such as use of ultraviolet-reflective mulches and interrow soil covers, have been effective means to reduce virus incidence in cucurbit crops

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Michael G. Bausher

consisted of a rank sum test of disease incidence using the Mann-Whitney rank-sums test using Systat 3.5 (Systat Software, San Jose, CA). Analysis for randomness was performed using the ordinary runs test to analyze the pattern of occurrence of virus

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Paul W. Bosland and Carl A. Strausbaugh

, BSCTV, and BMCTV. They found that ≈19% of symptomatic chile pepper plants had BMCTV, 48% had BSCTV, and 33% of the chile plants had a mixture of the two virus species. In 2010, again a year with high curly top incidence, chile pepper fields at the

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Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Fernando Rubio, Manuel Valero, and Juan J. Ruiz

. Use Breeding line UMH 1200 has genetic tolerance/resistance to the three most important viruses in tomato in southeastern Spain. The incidence of these viruses greatly reduces the profits obtained by farmers and even makes the cultivation of landraces

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Mohsen Mohseni-Moghadam, Christopher S. Cramer, Robert L. Steiner, and Rebecca Creamer

were to screen onion germplasm for IYSV tolerance/resistance in terms of disease severity and incidence to determine the correlation between severity ratings and a measure of virus titer in the plant and to determine the relationship of plant sampling

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T.W. Zimmerman and J.A. Kowalski

Demand for locally produced papaya fruit (Carica papaya) far outweighs the supply in the U.S. Virgin Islands. Due to the high incidence of papaya ringspot virus (PRSV), papayas are grown as an annual crop. The need exists in the Virgin Islands for papayas with early production to ensure a marketable crop before being devastated by PRSV. Breeding and selection has been ongoing for 5 years to develop papayas with tolerance to PRSV and fruit production starting at or less than 60 cm from the ground. The height at first fruit set, of 15 papaya cultivars recommended for the Virgin Islands, ranges from 58 cm to 253 cm. Generally, female plants started setting fruit lower on the stem than hermaphroditic plants. Through breeding and selection, three papaya lines have been developed that set the first fruit between 40 and 60 cm from the ground and exhibit tolerance to PRSV. These low-bearing papaya lines produce fruit that are marketable 1 month earlier than other cultivars.

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Janet Caprile and Steve Grattan

In areas of California with a high incidence of walnut blackline disease, walnut orchards are increasingly being planted on English walnut (Juglans regia) rootstocks that are tolerant to the virus. There is limited documentation on the salt tolerance of this rootstock. This work was done to quantify the response of English walnut rootstocks to high boron (B), chloride (Cl), and sodium (Na) and to compare this to the more common rootstocks, Northern California Black (J.hindsii) and Paradox (J. hindsii × J. regia). The trial was configured as a randomized complete-block design with 20 plots. Plots consisted of three proximate, matched `Chandler' trees, each on a different rootstock. Leaf samples over a 2-year period showed that trees on the English rootstock had a significantly higher salt uptake than trees on Paradox, which had a significantly higher uptake than trees on Black. Bark cores showed little difference in B uptake between any of the rootstocks. Bark cores also showed that all rootstocks accumulated significantly more B than the scion portion of the tree, indicating that B transport may be limited by the graft union. Trees on English rootstock had significantly more B in the scion bark cores than trees on either Black or Paradox, indicating that rootstocks with a J. hindsii parent may be better at reducing salt transport across the graft union.

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S. Alan Walters

The author wishes to thank Dena Fiacchino, Harry Riddle and Joyce Swenson for their technical assistance in this study, and Houston Hobbs of the University of Illinois-Dept. of Crop Sciences for virus determination. The use of trade names in this