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Vector Relationship of Graminella nigrifrons to Maize Chlorotic Dwarf Virus. M. M. Choudhury, Former graduate research assistant, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762, Present address of senior author: EMBRAPA-Centro Nacional de Pesquisa Agropecuaria do Tropico Semi-Arido, Petrolina, Pernambuco, Brazil; Eugen Rosenkranz, plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, and professor, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. Phytopathology 73:685-690. Accepted for publication 19 November 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-685.

In laboratory colonies, where the ratio of males to females was normally 2:1, 34- 35% of adult Graminella nigrifrons transmitted maize chlorotic dwarf virus (MCDV). There was a statistically significant difference between the rate of MCDV transmission by females (46%) and that by males (29%). While all five nymphal instars transmitted MCDV, the last three instars were as efficient vectors as adults. Noninfective adult leafhoppers acquired MCDV from diseased corn plants in as little as 15 min. The frequency of transmission increased with extension of the acquisition access period (AAP). Viruliferous adult leafhoppers infected corn seedlings during an inoculation access period (IAP) of 15 min. No latent period of MCDV in G. nigrifrons could be demonstrated; transmission occurred after 1 hr AAP and 0.5 hr IAP. The minimum incubation period of MCDV in sweet corn was 6 days at a temperature range of 20- 32 C. The longest tested retention period of MCDV in G. nigrifrons was 37- 40 hr, but most transmitters lost their inoculativity earlier. Noninfective leafhoppers recovered MCDV from inoculated corn plants 3- 5 days before first symptoms appeared. There was no transovarial passage of MCDV in G. nigrifrons reared on infected plants. Inoculative nymphs lost inoculativity immediately upon molting. When MCDV-infective adult G. nigrifrons were confined to healthy corn test plants, they retained infectivity for up to 2 days, then lost it and remained noninfective during the next day. After that they began to reacquire the virus from the same test plants. Thus, transmission data from tests involving transfers at intervals of more than 3 days may suggest that MCDV is being transmitted by G. nigrifrons in a persistent manner. In reality, all aspects of the transmission process reveal a relationship between MCDV and G. nigrifrons that is not persistent and is best described as transient or transitory.

Additional keywords: ecdysis, efficiency of transmission, Ohio corn stunt agent, Zea mays L.