Transmission Biology of Maize Bushy Stunt Phytoplasma by the Corn Leafhopper (Homoptera: Cicadellidae)

Abstract

Effects of temperature and vector age at the time of acquisition on the transmission of maize bushy stunt phytoplasma by the corn leafhopper, Dalbulus maidis (DeLong & Wolcott), were studied. Mean latent period in the leafhopper and transmission rate of the Tlaltizapan maize bushy stunt phytoplasma isolate had a quadratic relation with temperature. Mean latent period was inversely related to temperature from 15 to 25°C. Transmission rate was highest at 20 and 25°C and lowest at 15 and 30°C. The Tlaltizapan isolate was transmitted better when maize bushy stunt phytoplasma was acquired as nymphs than as adults at 15, 20, and 25°C. The transmission biology of 3 maize bushy stunt phytoplasma isolates by D. maidis was compared when leafhoppers acquired phytoplasma as nymphs and were held at 15 and 25°C. Differences among the 3 isolates were found only at 25°C. At this temperature, the Poza Rica isolate had a longer mean latent period and higher transmission rate than the El Batan and Tlaltizapan isolates. Moreover, the Poza Rica isolate had a longer incubation period in the plant host and produced more basal tillering in infected maize than did the other 2 isolates. Based upon biological findings in this study, as well as molecular studies reported elsewhere, we propose that maize bushy stunt phytoplasma has a polyphyletic origin and evolved from strains of the aster yellows phytoplasma.