Effects of graft and aphid transmission on the genetic diversity and population structure of Turkish citrus tristeza virus isolates


Korkmaz S., Karanfil A., Satar S., Uslu T., Koç N. K., Çevik B.

EUROPEAN JOURNAL OF PLANT PATHOLOGY, vol.162, pp.369-388, 2021 (SCI-Expanded)

Abstract

Citrus tristeza virus (CTV) causes the most destructive viral disease of citrus and is trans mitted by grafting and multiple aphid vectors. The
mode of transmission is important for the epidemi-
ology, genetic diversity, and evolution of viruses.
Therefore, the effects of graft and aphid transmission
on the population structure of Turkish CTV isolates
were evaluated in this study. First, molecular, and bio-
logical characteristics of original field isolates (OR) collected from five different citrus growing regions
were determined. Then, they were all grafted onto
Madam Vinous sweet orange and the 24 graft-trans-
mitted (GT) isolates were obtained and maintained.
When 24 GT isolates were transmitted to Mexican
lime seedlings by Aphis gossypii, 30 sub-isolates
(AT) were obtained from 15 aphid-transmissible iso-
lates. The CP genes of all OR isolates their GT and
AT sub-isolates were amplified by RT-PCR, cloned,
and sequenced and compared with each other and
well-characterized type strains. The changes in popu-
lation structure of isolates and sub-isolates were ana-
lyzed. While genetic diversity was increased by graft
transmission, it was reduced to the level of the origi-
nal isolates after aphid transmission. Comparisons of
the phylogenetic grouping and the genotype profiles
of the OR isolates and their GT and AT sub-isolates
showed a partial or complete genotype shift in some
isolates. The results suggested that mode of transmis-
sion may play a role in changes in the genetic diver-
sity of CTV isolates.