TITLE:
Geographical Variation, Distribution and Diversity of Rice Yellow Mottle Virus Phylotypes in Tanzania
AUTHORS:
Judith Hubert, Herman J. F. Lyimo, Ashura Luzi-Kihupi
KEYWORDS:
Rice Yellow Mottle Virus, Prevalence, Severity, Environmental Factors, Tanzania
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.6,
May
23,
2017
ABSTRACT: Rice yellow mottle virus (RYMV)
is the most important disease of rice in Africa. The disease was first observed
in1966 inKenya but has now spread in all rice-growing countries of Sub-Saharan Africa.
In Tanzania, its distribution has been restricted to the major rice-growing
regions. However, the knowledge on RYMV genetic diversity relies on a limited
number of coat protein sequences. Previous studies revealed the presence of the
phylotypes S4lv, S4lm and strain S5 in Mwanza, Mbeya and Morogoro regions,
respectively, and strain S6 in Kilimanjaro region and Pemba Island. Surveys
were conducted during the cropping seasons 2013-2014 in eight rice-growing
regions of Tanzania to determine geographical variations and phylotypes of RYMV
and the influence of environment factors on its distribution and diversity. A
total of 185 rice fields were surveyed. Results indicate that prevalence,
severity and phylotypes of RYMV varied significantly with rainfall intensity,
temperature and relative humidity (P ≤ 0.01). The highest prevalence was found
in Morogoro (82%), Mbeya (80%) and Arusha (67.33%) regions whereas Kigoma
(9.33%), Rukwa (11.33%) and Shinyanga (18.67%) had the lowest RYMV prevalence.
In each region, RYMV prevalence was higher in 2014 than in 2013. The phylotypes
S4lm and new determined phylotypes (S6c and S6w) were highly adapted to
low temperature (13.3°C) and rainfall (13.7 mm) areas. For the first
time, strains from the phylotype S4ug were found outside Uganda, in Kilimanjaro
region. Strain S4lv (phylotype Lake Victoria) was found for the first
time in Arusha region. The strain S4lm was found in Mbeya, Morogoro and Rukwa
regions. Strains S4lm and S4lv were also found in Shinyanga and Kigoma regions,
respectively. The strain S5 was still restricted to Morogoro but extended to
new locations such as Ulanga district. Strain S6 was found in several new areas
and new phylotypes of S6 (S6c and S6w) are reported in this study.