Characterization and Field Studies of a Cucumber Mosaic Virus Isolate ,from Spinach in the Winter Garden Area of Texas

Wilson, A. D., and Halliwell, R. S. 1985. Characterization and field studies of a cucumber mosaic virus isolate from spinach in the Winter Garden area of Texas. Plant Disease 69:751-754. An isolate of cucumber mosaic virus (CMV) was identified from spinach in the Winter Garden area a of Texas. The isolate was very closely related serologically to strain S of CMVand is designated the Texas spinach isolate of CMV-S. The virus infected 39 species of crop plants and wild hosts in 12 of 13 families tested. The green peach aphid efficiently transmitted the virus experimentally. The isolate had a sedimentation coefficient of 91.8 f 0.1 S as determined by analytical ultracentrifugal analysis. Virions with a mean diameter of 28.9 f 0.3 nm were found in purified preparations with electron microscropy. A single protein subunit with a mean molecular weight of 25,300 + 255 daltons was found by sodium dodecyl sulfate polacrylamide gel electrophoresis (SDS-PAGE). Four separate RNA species were resolved by agarose-gel electrophoresis under denaturing conditions. The mean molecular weight distribution of the viral genome was 1.22, 1.09,0.77, and 0.36 X IO6 daltons. CARNA 5 was not jointly encapsidated with theviral genome. In the field studies, planting date and plant age at inoculation had no significant effect on crop yield, although CMV infection was highly significant. The isolate significantly affected yields of three spinach cultivars, with reductions ranging from 23.8 to 47.4%. Additional key words: spinach blight, Spinaciu oleracea Spinach L.) was the obtained. Infected spinach plants not third most economically important only showed the famil iar spinach bl ight vegetable crop for fresh market in Texas symptoms most commonly associated for 198 1. About 22,000 t of fresh-market with CMV but also showed systemic spinach were produced in Texas in 198 I mottling, acute veinal distortion, or with a market value exceeding $18 severe leaf narrowing, distortion, and leaf million (11). The two major production curling. The range and variability of areas in the state, the Winter Garden and symptoms expressed in different spinach the Lower Rio Grande Valley, account cultivars were examined, and the effect of for about 45% of the total fresh-market the virus on yields of selected spinach spinach acreage harvested in the United cultivars was determined under field States (1). condi t ions . Five viruses are presently known to contr ibute consis tent ly to yield losses of spinach each year in Texas. They are beet curly top virus, cucumber mosaic virus (CMV), spinach yellow dwarf virus, tobacco ringspot virus (9), and a newly described isometric virus, as yet unnamed, which has severely affected spinach production in southern Texas (5). In a , In this paper, we characterize the spinach blight virus with host range, vector transmission studies, analytical ultracentrifugal analysis, electron microscopy, serology, and electrophoresis. Furthermore, we demonstrate yield losses of commercial spinach cultivars at tr ibuted to the CMV isolate . survey during the 1979-1980 winter growing season, a new virus isolate was MATERIALS AND METHODS This research was supported in part by the Del Monte Corp. and the Chevron Chemical Corp. Mention of a commercial company or manufactured product does not imply endorsement by the Texas Agricultural Experiment Station over other products or companies not mentioned. Virus isolate source. The isolate characterized in this paper was obtained in February 1980 from naturally infected spinach plants. The virus was collected within the Winter Garden area in Zavala County, TX, and maintained on Nicotiana tabacum L. ‘Samsun NN.’ For purification purposes, the virus was propagated in tobacco cult ivar Xanthi NN. Accepted for publication 13 March 1985 (submitted for electronic processing). Thepublicationcostsofthisarticleweredefrayedinpart by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. g 1734 solely to indicate this fact.