Geographical Variation, Distribution and Diversity of Rice Yellow Mottle Virus Phylotypes in Tanzania

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DOI: 10.4236/ajps.2017.86084    1,416 Downloads   2,779 Views  Citations

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.

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Hubert, J. , Lyimo, H. and Luzi-Kihupi, A. (2017) Geographical Variation, Distribution and Diversity of Rice Yellow Mottle Virus Phylotypes in Tanzania. American Journal of Plant Sciences, 8, 1264-1284. doi: 10.4236/ajps.2017.86084.
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