More than 300 red raspberry cultivars and selections were screened for raspberry (Rubus idaeus L.) bushy dwarf virus (RBDV), tobacco streak virus (TSV), and tomato ringspot virus (TomRSV) using enzyme-linked immunosorbent assay in three naturally infected breeding program selection plots at Corvallis, Ore. All genotypes tested negative for TSV and TomRSV. The RBDV incidence in primocane-fruiting cultivars and selections was 67%; in floricane-fruiting genotypes, it was 34%. The pattern of RBDV infection in the field showed no discernible trend. The high incidence may have been due to use of infected parents, propagation of infected genotypes, and pollen transmission. `Willamette', considered to be immune to the common strain of RBDV, along with 14 clones that had been in the field 10 years or longer, tested negative. The high incidence of RBDV in the breeding plots may provide an opportunity to identify resistant parents for breeding programs. An early seedling screening method for RBDV susceptibility is desirable to eliminate highly susceptible genotypes from the program and maintain a lower incidence of RBDV within the breeding plots.
M.M. Stahler, F.J. Lawrence, and R.R. Martin
W.B. Evans, D.M. Ingram, C. Waldrup, B. Layton, A. Milling, T. Bishop, and V. Lee
Mississippi's two largest tomato-growing areas are in Smith and George Counties. The Truck Crops Branch Experiment Station in Crystal Springs is the closest vegetable research site to Smith County but does not share the same soil type. Tomato spotted wilt virus (TSWV) reduces fruit yield and marketability, and its incidence appears to be increasing in the state. The objectives of this trial were 1) to determine fruit yield and TSWV incidence in tomatoes (Lycopersicon esculentum) grown in central Mississippi, and 2) compare yield and relative yield among cultivars and between locations. Tomato seedlings were transplanted to the field in April 2004 in Smith and Copiah County plots. Production practices included raised beds, black plastic mulch, drip irrigation, and fertilizer applied pre-plant and as side-dressings based on soil test and regionally recommended practices. TSWV incidence was recorded in each plot in Smith Co. in June 2004. In both locations, `Amelia' and `Mountain Spring' were among the top yielding entries. In Smith, the top entries also included `BHN 543' and two commercial experimental entries. In Copiah, `Florida 47 R', `Biltmore', `Mountain Fresh', and `BHN 543' also produced high marketable yields. `Florida 47R', `Bush Celebrity', and `Mountain Fresh' were among the poorest yielding varieties in Smith County. Incidence of TSWV was not formally rated in Copiah. In Smith, percent symptomatic plants per plot were negatively correlated with yield. Symptoms were found on entries reportedly resistant or tolerant to TSWV.
Rebecca Creamer, Soumaila Sanogo, Osama A. El-Sebai, Jared Carpenter, and Robert Sanderson
Kaolin reflectant treatments have been shown to reduce stress due to the environment, pests, and pathogens in many plants. We tested the effect of kaolin on yield, beet curly top virus (BCTV) incidence, and physiological parameters (measured as hyperspectral reflectance) of field-grown chile pepper (Capsicum annuum L.) in southern New Mexico. Curly top incidence was significantly lower in kaolin-treated chile blocks than untreated blocks. Peppers treated with the kaolin-reflectant showed significantly less water stress and higher photochemical reflectance than untreated plants during active growth periods. Treated plants had significantly higher levels of chlorophyll a and higher reflectance than untreated plants. Yield from treated plants was not significantly different from that from untreated plants. We did not detect any deleterious effects on peppers due to application of kaolin. Kaolin treatments suppressed beet curly top virus on chile and reduced water stress parameters during the hottest months of the growing season, suggesting that it would be useful in New Mexico chile production in years with moderate disease pressure.
C. Avilla, J.L. Collar, M. Duque, P. Pérez, and A. Fereres
A.D. Bryan, Z. Pesic-VanEsbroeck, J.R. Schultheis, K.V. Pecota, W.H. Swallow, and G.C. Yencho
Decline in sweetpotato yield and storage root quality has been attributed to the accumulation of viruses, pathogens and mutations. To document the effects of decline on yield and storage root quality, two micropropagated, virus-indexed, greenhouse produced G1 `Beauregard' meristem-tip cultured clones, B94-14 and B94-34, were compared with 1) micropropagated B94-14 and B94-34 clones propagated adventitiously up to five years in the field (G2, G3, G4, G5); and 2) nonmicropropagated, unimproved stock of `Beauregard' seed in field trials during 1997 to 2001. At least three trials were located each year in sweetpotato producing regions in North Carolina. In 2000 and 2001, two trials were monitored weekly for foliar symptoms of Sweet potato feathery mottle virus (SPFMV) and other potyviruses, and virus-indexed for selected viruses using Ipomoea setosa and nitrocellulose enzyme linked immunosorbant assays (NCM-ELISA). Only SPFMV was detected in field samples using NCM-ELISA, but this does not rule out the presence of newly described viruses infecting sweetpotato for which tests were unavailable. Monitoring indicated that all G1 plants became infected with SPFMV by the end of the growing season, and that G2 to G5 plants were probably infected in their initial growing season. G1 plants consistently produced higher total yield, total marketable yield (TMY), U.S. No. 1 root yield and percent No. 1 yield than G2 to G5 plants. G1 plants also produced storage roots with more uniform shapes and better overall appearance than storage roots produced from G2 to G5 plants. Also, G2 to G5 storage roots tended to be longer than G1 storage roots. Rank mean yield and storage root quality measurements of each location were consistent with means averaged over locations per year and suggested a decrease in yield and storage root quality with successive seasons of adventitious propagation. Linear regression analysis used to model yield and storage root quality measurements of seed generations G1 to G5 indicated that total yield, TMY, No. 1 yield, percent No. 1 yield, shape uniformity, and overall appearance decreased gradually, and that length/diameter ratios increased gradually with generation. The rate of decline in No. 1 yield was greater for B94-34 compared to B94-14. Both viruses and mutations of adventitious sprouts arising from storage roots probably contribute to cultivar decline in sweetpotato, but further studies are needed to determine their relative importance. A simple profitability analysis for G1 vs. G2-G4 planting material conducted to facilitate better understanding of the economics of using micropropagated planting material to produce a crop in North Carolina revealed that growers have a potential net return of $2203/ha for G1 plants, $5030/ha for G2 plants, and $4394/ha for G5 plants. Thus, while G1 plants generally produce higher No. 1 yields, a greater monetary return can be achieved using G2 planting materials because of the high costs associated with producing G1 plants. Based on this analysis, the best returns are accrued when growers plant their crop using G2 and/or G3 seed.
, England. Paper No. IITA/95/CP/15. I thank F. Gauhl, C. Pasberg-Gauhl, and D. Vuylsteke (IITA) for data collection on virus incidence in multilocational trials. Also acknowledged is the cooperation of partners in African National
Sahar Eid, Keri L. Druffel, Dayle E. Saar, and Hanu R. Pappu
obtained from each of the primer pair used and the sequence results verified their identity. DCMV was the second most frequent virus, after DMV-D10, found during the survey ( Fig. 2 ). Mixed infections were common. The frequency of incidence of DMV alone
Christopher A. Clark, Tara P. Smith, Donald M. Ferrin, and Arthur Q. Villordon
-infection of their seed. Preliminary evaluations indicated that low incidence of re-infection with viruses can occur during the production of G1 foundation seed. However, there was little information available to evaluate how rapidly seed productivity and
Cindy B.S. Tong, Hsueh-Yuan Chang, James J. Luby, David Bedford, Benham E.L. Lockhart, Roy G. Kiambi, and Dimitre Mollov
. Al Shoffe et al. (2016) documented a chilling disorder that they labeled “wrinkly skin” in ‘Honeycrisp’ apple fruit, which may be the same disorder as skin dimpling. In previous studies, skin dimpling was associated with several viruses and viroids
Clinton C. Shock, Erik Feibert, Lynn Jensen, S. Krishna Mohan, and Lamont D. Saunders
reduced yield and reduced bulb size. The virus is transmitted by onion thrips ( Thrips tabaci ) ( Kritzman et al., 2001 ; Nagata and Almeida, 1999 ). The incidence of IYSV might be increased by the inadequate control of onion thrips, which have become