Phylogenetic Analysis of Fusarium oxysporum f. sp. cubense Associated with Fusarium Wilt of Bananas from Peninsular Malaysia

Abstract

Fusarium wilt of bananas caused by Fusarium oxysporum f. sp. cubense (Foc) has been known to hamper banana production. In Malaysia, most of the edible banana cultivars are susceptible to the fungal strain Foc tropical race 4 (Foc TR4). To date, molecular characterisation of Foc TR4 in this country remains elusive. Thus, this study aimed to characterise the diversity of Foc TR4 in Peninsular Malaysia based on the phylogenetic analysis of transcription elongation factor (TEF-1α) sequences.

Current Classification and Diversity of Fusarium Species Complex, the Causal Pathogen of Fusarium Wilt Disease of Banana in Malaysia

“…The result produced a more specific finding from the TEF-1α analysis as this could be due to the high volume of research conducted on the identification of Fusarium spp. Thus, this gene yielded more datasets for comparison [6,9,10,16,27,29]. One possible reason for the better result obtained using TEF-1α is that this protein is highly conservative and was identified as an essential genetic marker in the Fusarium study [12,30].…”

“…Pathogenicity test was conducted over 30 days in triplicate by using an isolate that was confirmed to be of high virulence [10] on five different cultivars of local banana, consisting of banana plantlet of genome type AAA (Dwarf Cavendish), AA (Lakatan), AAB (Raja and Laknau), and ABB (Saba). The inoculum was the conidial suspension of F. odoratissimum (MUCC2841), which was prepared by mung bean medium (MBM: 5 g mung bean with 1 L of ddH 2 O) [27].…”

“…The severity of wilting was rated following the disease scale, where 1 indicates no symptom/healthy, 2 denotes initial yellowing mainly on the lower leaves, 3 means yellowing of all the lower leaves, including some discolouration on the younger leaves, 4 indicates intense yellowing on all leaves, and 5 means "plant dead" or complete wilting [10]. Additionally, pseudostem splitting was observed, and the plantlet was uprooted, cleaned, and cut at rhizome, observing for corm rot, and rated as the following: 1 indicates no discolouration observed, 2 means discolouration on isolated points, 3 denotes about 30% discolouration, 4 indicates up to 50% discolouration, 5 means discolouration up to 90%, and 6 denotes plant decay [27].…”

“…Although the degree of severity of the foliar symptom varied at the different cultivars, the internal symptoms of all cultivars showed severe corm rotting and discolouration (Figure 5c,f,i,l,o). a Severity of wilting was rated following the disease scale [10]; 1: no symptom/healthy, 2: initial yellowing mainly on the lower leaves, 3: yellowing of all the lower leaves including some discolouration on the younger leaves, 4: intense yellowing on all leaves, 5: plant dead/complete wilting. b Corm rot severity was rated following the disease scale [27]: 1 indicates no discolouration observed, 2 means discolouration on isolated points, 3 denotes about 30% of discolouration, 4 indicates up to 50% discolouration, 5 means discolouration up to 90%, and 6 denotes corm decay.…”

“…In Malaysia, several studies of the genetic diversity of Foc have been conducted based on the molecular phylogeny and VCG analyses, and those results suggest the existence of highly divergent variations of strains of Foc-TR4 (F. odoratissimum) [9,10]. Morphological characterization is a fundamental initial classification that has been used to identify the fungal at the species level [11].…”