2.2.129
VEGETATIVE COMPATIBILITY IN A POPULATION OF COLLETOTRICHUM KAHAWAE FROM KENYA
VEGETATIVE COMPATIBILITY IN A POPULATION OF COLLETOTRICHUM KAHAWAE FROM KENYA
E K GICHURUl VMP VARZEA2 CJ RODRIGUES Jr 2 and D M MASABAl
lCoffee Research Station P 0 Box 4, Ruiru, Kenya 2IICT-Centro de lnvestigacao das Ferrugens do Cafeeiro, Quinta do Marques. 2780 Oeiras, Portugal
Background and objectives
Three species of Colletotrichum namely C. gloeosporioides, C. acutatum and C. kahawae are usually isolated from coffee trees. From these species C. kahawae is the causal agent of the Coffee Berry Disease (CBD) firstly reported in Kenya in 1922 and present nowadays in all African Arabica coffee producing countries where it is its main limiting factor at high altitudes. The disease causes losses of 70% when the epidemic conditions are favourable and there is no adequate intensive fungicide spraying. Nitrate non-utilizing mutants have been extensively used to study vegetative compatibility among populations of phytopathogenic fungi, including C. gloeosporioides and C. kahawae [1],[21 and to get some information on possible genetic relationships. The objective of this work was an attempt to comprehend the possible relatedness among isolates of C. kahawae collected in different coffee regions of Kenya.
Materials and methods
Thirty-nine single spore isolates of C. kahawae, one of C. gloeosporioides and one of C. acutatum were subjected to chlorate mutagenesis to produce nitrate non-utilizing mutants. In order to test the vegetative compatibility of the isolates, nitl and NitM mutants were selected and paired in a minimum medium having nitrate as the sole nitrogen source. The growth in the contact zone of a dense aerial mycelium was an indication of complementation.
Results and conclusions
All the isolates of C. kahawae were compatible amongst themselves and therefore were included in the same Vegetative Compatibility Group (VCG). The isolates of C. gloeosporioides and C. acutatum were incompatible between them and incompatible with all the other isolates of C. kahawae forming thus two distinct VCGS.
References
1. Brooker NL., Leslie JF, Dickman, MB. 1991. Phytopathology 81:672-675
2. Beynon SM. Coddington A., Lewis BG, Varzea V. 1995. Physiological and Molecular Plant Pathology 46:457-470