**7. Conclusions**

*Genetic Variation*

relationships between them.

diversity at the center of origin of bananas.

VCGs [32, 36, 42, 44, 50, 53].

now clearly belong to clade 2 [55].

alleles with VCG 0124 [47]. On the other hand, the pathogenicity studies with representative isolates of each VCG in Cuba, showed a differentiated aggressiveness on different clones between VCG 0124 and 0128, belonging to race 2, indicating lack of genetic sense in the racial classification. It is required to determine in Latin America and the Caribbean the VCG present in the different countries and the pathogenic

In order to better understand how races 1 and 4 are related, genome and transcriptome analysis of *F. oxysporum* f. sp. *cubense* has shown common sequences of single-copy genes from Race 1 and Race 4, showing that there is a close relationship and suggesting that they share a common ancestor. Furthermore, a comparative genomics study among *F. oxysporum* f. sp. *licoperci*, *F. graminearum* and *F. verticillioides* showed that there is transfer of lineage-specific (LS) genomic regions that have pathogenicity related genes with distinct evolutionary profiles, indicative of horizontal acquisition and suggesting that there is transfer of LS chromosomes between genetically isolated *Fusarium* species. This is of high relevance and of particular concern for agricultural systems, because non-pathogenic *F. oxysporum* strains that are already endophytic to crop plants could suddenly become pathogenic [48] and give origin to new pathogenic lineages of *F. oxysporum*. It is clear that in the last decade a large amount of DNA sequence information has been published on *F. oxysporum*, but there is a lack of consistency in the data and a larger study needs to be conducted in which DNA sequences of isolates from non-cultivated species is included and even from *Fusarium* species that are thought not to be related. Foc genetic diversity studies were initiated using various molecular methods, including random amplified polymorphic DNA markers (RAPDs) [49]; Restriction Fragment Length Polymorphisms (RFLP) [43]; Amplified fragment length polymorphism (AFLP) [50]; DNA sequence analysis [32, 44]; microsatellites or simple repetitive sequences [51]; simple repetitive inter sequence (ISSR) [52]. These studies showed that the population of this fungus in Southeast Asia shows a high degree of variation, suggesting that the Foc lineages evolved together with their hosts in Southeast Asia. Alternatively, Foc has been suggested to have multiple independent evolutionary origins, both within and outside the *Musa* genetic center [36]. Using the phylogenetic genealogical approach, [32] identified five Foc-independent genetic lineages in a global population. Using a similar approach and additional data, [44] found three additional lineages. However, none of these studies included Indonesian populations, and therefore there is only limited information available on Foc

*F. oxysporum* f.sp. *cubense* probably coevolved with its host species within its center of origin [32, 36, 44]. For example, various studies that have used deoxyribonucleic acid (DNA) markers have revealed the polyphyletic origin of Foc and the separation of two main clades and eight to ten lineages, as some VCGs are taxonomically closer to other special forms of *F. oxysporum* than some Foc

Furthermore, strains belonging to various VCGs infect particular banana cultivars and, therefore, were grouped in the same race, suggesting that the pathogenicity towards a specific cultivar evolved in a convergent way [32, 38, 44] or as a result of horizontal gene transfer between members of the *F. oxysporum* complex [48, 54]. High resolution genotyping sequencing analyzes using (DArTseq) validated and expanded these findings [55]. According to the DArTseq markers of 24 Foc strains (representing all the known VCG so far) they were divided into two groups. These results strongly corroborate the clades mentioned in previous studies, except VCG0123, VCG01210, VCG01212 and VCG01214, which were occasionally grouped into opposing clades, VCG 01221 and 01224, which were never classified before but

**136**

Fusarium wilt disease of banana caused by soil-born pathogen *Fusarium oxysporum* f.sp. *cubense* (Foc) is considered of the most destructive diseases of bananas and plantains worldwide. Foc produces three types of asexual spores, these are macroconidia, microconidia and chlamydospores, which function as mechanisms of dispersal, reproduction and survival. Foc is a genetically diverse pathogen, although the available evidence so far indicates that it does not use the mechanisms of sexual reproduction, such as recombination, to increase its genetic diversity. Furthermore, the population of this fungus in Southeast Asia shows a high degree of variation, suggesting that Foc lineages evolved together with their hosts in Southeast Asia. Alternatively, it has been suggested that Foc has multiple independent evolutionary origins, both within and outside of the Musaceae origin center. Actually, more than 24 vegetative compatibility groups and three races have been reported. This genetic diversity is accommodated in two large clades and nine clonal lineages.

*Genetic Variation*
