Morphological Features and Germinability of Head and Loose Smut Pathogens in Nigerian Sudan Savanna

Abstract

There are considerable experimental and field evidences that physiologic race differences exist amongst sorghum smut pathogens  infecting both sorghum and maize in many parts of the world. In Nigeria, several researches have been conducted in the areas of  epidemiology of many crop plant diseases, but less attention is been paid to some important aspects of the biology of smut fungi. Studies  were conducted on the morphological features and germinability of the teliospore samples of Sporisorium cruenta and   Sporisorium reilianum; the causal agents of sorghum loose and head smuts; respectively. One composite teliospore sample each of S.  cruenta and S. reilianum was collected from 12 locations that were at least 70 km apart on a road network, in the Sudan savanna Agro-ecological zone of Nigeria. Aspects of spore color, length, width, and shape as well as germinablity of the spore in water and PDA of the  various samples were determined. The color of both S. cruenta and S. reilianum teliospore was dark in aggregates and dark brown when  single. The length and width of S. cruenta and S. reiliana teliosores averaged to 5.7 X 4.1µm while the shape ranged from irregular,  spherical, and echinulate. In S. reilianum the mean size of the spore was 9.1 x4.3 µm. Its structure generally ranged between ovoid to  spherical and hyaline.in both PDA and water, S. reilianum germinated faster than S. cruenta teliospores with significant (P≥0.05) difference  between the various teliospore isolates. This result connotes that there are morphological differences between the various  isolates of the same and between different pathogens. The results have shown that both spore isolates of S. cruenta and S. reiliana were alive and that the teliospore of S. reilianum germinated faster and hence might cause disease faster than S. cruenta teliospore in this  region.