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The Erwinia species are well-known pathogens of economic importance in Malaysia causing serious damage to high-value fruit crops that include pineapple [Ananas comosus (L.) Merr.] and papaya (Carica papaya L.).The 16S rRNA sequence using eubacteria fD1 and rP2 primers, identified two bacteria species; Dickeya zeae from pineapple heart rot, and Erwinia mallotivora from papaya dieback. Phylogenetic analysis based on the neighbor-joining method indicated that all the bacterial isolates clustered in their own taxa and formed monophyletic clades. From the pathogenicity test, all isolates of D. zeae and E. mallotivora showed pathogenic reactions on their respective host plants. Genetic variability of these isolates was assessed using repetitive sequence-based PCR (rep-PCR) fingerprinting. The results indicated interspecies, and intraspecies variation in both species’ isolates. There were more polymorphic bands shown by rep-PCR fingerprints than enterobacterial repetitive intergenic consensus (ERIC) and BOX- PCRs, however both species’ isolates produced distinguishable banding patterns. Unweighted pair-group method with arithmetic averages (UPGMA) cluster analysis indicated that all Dickeya and Erwinia isolates from the same species were grouped in the same main cluster. Similarity among the isolates ranged from 77 to 99%. Sequencing of 16S rRNA using eubacteria fD1 and rP2 primers, and rep-PCR fingerprinting revealed diversity among Dickeya and Erwinia isolates. But this method appears to be reliable for discriminating isolates from pineapple heart rot and papaya dieback.
Isolates of Fusarium from rice, sugarcane and maize were identified as F. verticillioides, F. sacchari, F. proliferatum F. subglutinans, F. fujikuroi and F. oxysporum. The species were then characterized by restriction analysis of intergenic spacer (RFLP-IGS) using AluI, Eco88I, RsaI and XhoI. Twenty-five haplotypes were identified among the isolates of Fusarium which indicated high levels of variations. UPGMA cluster analysis was conducted to cluster the isolates and to estimate the intraspecific and interspecific variability. Isolates of F. fujikuroi from rice were clustered together with isolates of F. proliferatum from rice and maize with a similarity value of 88–100%. Isolates of F. verticilliodes from maize and sugarcane were clustered together with a similarity value ranging from 92–100%, and two isolates from rice formed another cluster. Isolates of F. oxysporum from maize and rice were clustered together with a similarity value ranging from 87–95%. Isolates of F. subglutinans from rice and maize, and F. sacchari from rice and sugarcane were also clustered together with a similarity value of 77–100%. Based on RFLP-IGS analysis, variability was observed within and between species of Fusarium from rice, maize and sugarcane and the technique could be use to complement morphological characterization and to determine genetic relationships between the species.
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