Problem statement: Fungal endophytes are widely studied for their potential as biocontrol agents towards fungal pathogens. In vitro assessments usually reveal their antibiosis and mycoparasitism nature, but little is understood regarding their production of volatile metabolites as mechanisms of antagonism. Approach: This study explored the potential of fungal endophytes in controlling the pathogen responsible for Fusarium wilt disease. Nine fungal endophytes were tested for their ability to inhibit the growth of the pathogenic Fusarium oxysporum F. sp. cubense race 4 (FocR4) via production of volatile inhibitory metabolites. The type of volatile metabolites produced were subsequently characterized and identified using the Gas-Chromatography Mass-Spectrophotometry (GCMS). Results: Eight of the isolates (BTF05, BTF07, BTF08, BTF15, BTF21, WAA03, WAA02, MIF01) showed positive results with percentages of inhibition varying from 1.43-31.43% while one isolate (ALF01), showed negative result (0% inhibition). Volatile profiles showed that these fungal endophytes produced between 15-47 volatile metabolites per isolate. However, the more volatile metabolites produced by a single endophyte does not indicate better biocontrol potential. Isolate BTF05 produced 47 different volatile metabolites, but has only 8.57% inhibition, compared to isolate BTF21 with 15 metabolites but a percentage of 11.43% inhibition. The potency of the volatile metabolites produced may also influenced the biocontrol potential of the fungal endophytes as some isolates such as BTF08 and MIF01 have only two to three known inhibitory metabolites but have higher PIDG values at 31.43 and 11.43%, respectively. Contrary, isolates WAA02 and WAA03 which has five to six metabolites but PIDG values of less than 3%. Conclusion: Fungal endophytes have the ability to produce several types of volatile metabolites to inhibit the growth of FocR4. These volatile inhibitory metabolites can be further extracted and the amount produced ascertained for future manipulation in biological control of FocR4.

A variety of volatile compounds were detected from six endobacteria isolated from different host species. From this, only two isolates (LCB01 and AVA02) produced volatile compounds capable of inhibiting the growth of the pathogenic Fusarium oxysporum f. sp. cubense race 4 (FocR4). Inhibition by volatile compounds produced by isolate LCB01 (Herbaspirillum spp.) was the most effective with 20.3% inhibition towards FocR4. Volatile compounds profiles indicated that inhibition may be attributed to the presence of single compounds such as 2-pentane 3-methyl, methanethiol and 3-undecene, or their action synergistically. Both methanethiol and 3-undecene were also produced by AVA02 (Pseudomonas spp.), but the absence of 2-pentane 3-methyl seemed to have affected the inhibitory effect with only 1.4% inhibition. The absence or the low levels of the three compounds in the other four isolates resulted in no inhibition of FocR4. These observations strongly suggest the antifungal nature of the three volatile compounds towards FocR4.

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