Random amplified polymorphic DNA analysis of genetic variability among isolates of Ganoderma species

Ganoderma wilt of coconut caused by Ganoderma lucidum (Leys) Karst, is the most serious disease constraint to coconut production throughout the world. The genus Ganoderma has a wide host range and shows morphological variability among the isolates from different hosts. Random amplified polymorphic DNA (RAPD) analyses were used to determine the genetic relatedness within and between G. lucidum isolates from infected coconut palm and Ganoderma sp. from other hosts from different locations in India. RAPD analysis using ten random primers showed variations of banding patterns within and between the isolates from coconut and other hosts, indicating that they were genetically heterogeneous. There was no specific banding pattern that could differentiate between G. lucidum isolates from coconut palm and Ganoderma sp. from other hosts. Dendrograms from cluster analysis based on unweighted pair-group method using arithmetic means (UPGMA) of RAPD data showed that G. lucidum isolates from infected coconut palm and Ganoderma sp. from other hosts did not cluster separately into two distinct clusters, but were clustered together, which indicated that both groups of Ganoderma are closely related. The similarity values from RAPD analysis showed a broad range of values from 44 to 77 percent for G. lucidum isolates from infected coconut palm and Ganoderma sp. from other hosts. The finding that the Ganoderma isolates from coconut stumps are closely related to Ganoderma isolates from other hosts would have an important bearing in the formulation of disease control measures and planting procedures, especially in areas where the previous crop was infected with Ganoderma disease.