TITLE:
Molecular Diversity of a Seemingly Altitude Restricted Ustilago kamerunensis Isolates in Kenya: A Pathogen of Napier Grass
AUTHORS:
Dennis O. Omayio, David M. Musyimi, Francis N. Muyekho, Samuel I. Ajanga, Charles A. O. Midega, Clabe S. Wekesa, Patrick Okoth, Innocent W. Kariuki
KEYWORDS:
Ustilago kamerunensis, Diversity, Altitude, Napier Grass, Milk
JOURNAL NAME:
American Journal of Molecular Biology,
Vol.8 No.2,
April
27,
2018
ABSTRACT: The Central region of Kenya which is the second
largest market oriented dairy zone, faces a threat in milk production. The
challenge is a disease known as the napier head smut caused by Ustilago kamerunensis. This fungal
microorganism is a facultative pathogen which has been reported to cause yield
losses in napier grass (Pennisetum purpureum)
ranging from 25% to 46% across the affected areas. Additionally, there are reports of
the continual spread of the disease into neighbouring county of Nakuru in Rift-Valley
region which is the leading milk producing zone in the country. This scenario
of spread is worrying combined with observation of variations in damage levels
of napier grass clones across the five counties of Central Kenya. These
observations led to the hypothesis that possible differences might be existing
among the Ustilago kamerunensis variants in Kenya. Further, the differences in biomass yield losses that are
within a certain percentage range mentioned-above, seemed to support the existence of possible differences.
Therefore, to inform effective integrated management strategies of the pathogen
in case it’s co-evolving, this study sought to determine the molecular
differences of Ustilago kamerunensis isolates in affected counties using ITS 1 and 2 regions which are spanned by
5.8S ribosomal RNA gene. The Ustilago
kamerunensis propagules were systematically collected from affected
counties’ hot spot areas for sequencing and phylogenetic analysis. The study
revealed the most affected areas to be within the mean altitude level of
1988.17 ± 71.97 metres above sea level. Further, differences in the growth in vitro and molecular characteristics
of the seemingly altitude restricted isolates were observed. The Kiambu,
Nyandarau and Nakuru counties isolates clustered together, whereas those of
Murang’a, Nyeri and Kirinyaga formed another clade. The sequences of sixteen Ustilago kamerunensis isolates were
deposited in GenBank with accession numbers ranging from MG722754 to MG722769. The results suggest the existence of possible
genetic divergence of the isolates which might be reflected in their pathogenic
potential too. Effective integration of management strategies is vital towards
slowing the phenomenon for an optimal mitigation of the disease in Kenya.