‘A complex relationship, Banana & Fusarium wilt in Indonesia’ is the full title of the thesis of Nani Maryani, and complex it is. Nani comes from Indonesia, the centre of origin of banana and thus, from the co-evolutionary standpoint also the centre of origin of major pathogens threatening the crop. She is the first person to make a comprehensive study of sympatric speciation of Fusarium spp. pathogenic on bananas in Indonesia.
Fusarium wilt is one of the most devastating plant diseases in agricultural history. In the beginning of 1960’s Fusarium wilt disease (also called Panama disease because of the first place it occurred) wasted around 40.000 ha of Gros Michel bananas. The fungus is particularly devastating because it stays for years in the soil.

The introduction of a resistant Cavendish banana saved the Latin American banana industry. But now a new strain of Fusarium, Tropical Race 4 (renamed as Fusarium odoratissimum in this thesis) is virulent to many bananas including the widespread Cavendish banana. TR4 is most devastating of course in countries where monocultures exist. In Indonesia many different varieties of bananas are grown practically everywhere, in backyards, in commercial plantations, in mixed cropping as weeds by the roadside etc. ‘In regions where hundreds of cultivated varieties are available, like in Indonesia, subsistence farmers simply choose resistant varieties to replace susceptible ones. This practice makes disease control difficult and influences the evolution of the pathogen in such environments.’ The old practice of farmers interacts in this way with modern ways of large scale banana production.

‘In this thesis we explore, exploit and analyse the diversity of Foc (Fusarium oxysporum f. sp. cubense (Foc) from natural ecosystems in indonesia where hundreds of local banana varieties are grown. This knowledge is of great importance for sustaining global banana production through advanced breeding programs’ writes Nani Maryani.
In her thesis Nani proposes the term complex to group several species with unifying characters of pathogenicity on bananas: Fusarium of Banana Complex (FuBC).
Her thesis gives a first impression of the enormous diversity of FuBC in the Indonesian centre of origin of banana. More than 200 Fusarium isolates from local varieties were isolated and several DNA loci sequenced. New species were named and described. In greenhouse experiments isolate-banana accession interactions were researched, giving an insight into pathogenic variation among indigenous Fusarium species and pointing to promising resistant banana varieties.

Yet it is only a start. This knowledge needs to be extended Nani emphasizes.’ Extending the knowledge on the extensive diversity of the causal fungi should bridge the gap of co-evolution with hundreds of bananas varieties.’ Indonesian banana germplasm is a source for resistance. That too should be explored in much more detail.

Coming to Wageningen and Utrecht to study the Fusarium of Banana Complex was very inspiring for Nani Maryani. She learned to be independent, she says. ‘When I came here I thought somebody would teach me and say: do this, do that. They didn’t teach me in that way. I learned to be independent, take my own decisions, do my own experiments. I am very grateful to have been able to study here. I had two good promotors: Gert Kema from Wageningen University and Pedro Crous from the Westerdijk Institute. The combination of experts in plant pathology and in mycology was very good for me. The only regret I have: I never learned to speak Dutch. I am returning to Indonesia but I definitely hope to continue the collaboration.’