Heterokaryon incompatibility and phenotypic characterisation of Aspergillus flavus isolates in low and high risk zones in Kenya

Alfred Mitemaa,b, Sheila Okothb, Revel Lyerb, Amelia Hilgartb and Suhail Rafudeenb

Author address: 

aMolecular and Cell Biology, University of Cape Town, Cape Town, Western Cape, ZA bUniversity of Nairobi, Kenya


Species Aspergillus flavus (A. flavus) has three morphotypes: S-, L- and SBG-type strains, with the first repeatedly being associated with acute aflatoxicosis. Aflatoxicosis in Kenya is a serious health problem with outbreak 317 cases and 215 deaths. In 2013, we choose to address this crisis by characterising the diversity of A. flavus isolates through comparison of vegetative compatibility groups (VCGs), phenotypic characteristics and mycotoxin profiles across various agricultural regions in Kenya where aflitoxicosis has occurred previously. Using diagonal transect random household sampling, Maize kernels were collected from Makueni, Homa Bay, Nandi, and Kisumu counties between November and December 2013. Out of 37 isolates, the nitrate non-utilising auxotrophs (nit mutants) complementation test revealed 20 VCGs. KVCG14 and KVCG15 had highest distribution frequency (n = 13; 10.8%) while KVCG10 and KVCG20 (n = 1; 0.8%) the least. Analyses of VCG diversity using the Shannon Index (H) showed that Nandi (H′= 0.108) and Kisumu (H′= 0.324) counties recorded the lowest and highest VCG diversities respectively. Results also showed that, with a few exceptions, within-county isolates were self-compatible but they were incompatible across any two adjacent counties and across all the sampled counties. Heterokaryon incompatibility in Nandi (n = 6; 67%) and Makueni (n =3; 33%) were the greatest and least respectively. Mycotoxin detection by coconut cream agar under UV light (365 nm) revealed blue fluorescence {(57%, n =21) aflatoxin B} and green {(43%, n =16) aflatoxin G}. The study further revealed L-, S- type strains (57%; n =21 and 7%; n =2) respectively. The findings of the study could provide reliable information in determining biocontrol strategies to mitigate aflatoxin contamination of maize by A. flavus in the studied counties.


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Full conference title: 

The Fourteenth International Aspergillus Meeting, Asilomar Conference Center, Pacific Grove, CA, USA
    • Asperfest 14 (2017)