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Some Effects of Temperature on Xiphinema americanum and Infection of Cucumber by Tobacco Ringspot Virus. L. B. Douthit, Research Assistant, University of Arkansas, Fayetteville 72701; J. M. McGuire, Professor, University of Arkansas, Fayetteville 72701. Phytopathology 65:134-138. Accepted for publication 21 August 1974. DOI: 10.1094/Phyto-65-134.

Xiphinema americanum acquired tobacco ringspot virus (TRSV) at 16, 22, 28, and 34 C, and transmitted at all temperatures except 16 C. The optimum temperature for acquisition and transmission was 28 C. After mechanical inoculation of cotyledons and symptom development, the titer of TRSV in the roots of cucumber did not differ greatly during a subsequent 10-day period at 16, 22, or 28 C, but it did decrease steadily at 34 C. Some cucumber plants grown at 16, 22, 28, and 34 C became infected after mechanical inoculation of roots with TRSV. Surviving nematodes recovered after 10-days of feeding access to cucumber ranged from 39-52% at 16, 22, and 28 C, but only 5% at 34 C. Poor survival of nematodes seems to be the sole reason for low levels of virus transmission at 34 C. Nematodes moved greater distances in sand as the temperature increased from 16 to 28 C. Some nematodes had moved at least 15 cm after 10 days at 16 and 22 C, and 17.5 cm at 28 C. Nematodes were attracted toward cucumber plants at 28 C, and to a lesser extent at 22 C. There was no indication of attraction toward plants at 16 C. It is postulated that differences in attractiveness of cucumber as a feeding host of X. americanum account for lower rates of acquisition and transmission of TRSV at temperatures below 28 C.