Analysis of efficacy of different Penicillium fungal species as bio-control agents against Fusarium oxysporum

Abstract

The fungal genus Penicillium and many other soil-borne fungi have widely been reported to create soil myco-ecological conditions that influence plant growth. These fungal species have been noted to have the ability to produce and release a diverse range of phytochemicals and exogenous compounds with variable physiological influence on plants, plant growth and other microbes. To positively utilize these unique characteristics of Penicillium species, the study was conceived and designed to investigate the suppressive effects of Penicillium and Aspergillus species against F. oxysporum f.sp. radicis lycopersici (FORL). Different experiments were carried out, i.e. (i) Isolation and identification of soil fungal isolates in the semi-arid agro-ecological region, (ii) Dual anti-fungal assessment of the isolates against F. oxysporum f.sp. radicis lycopersici (FORL), (iii) Analysis of isolates’ phytopathological safety on selected vegetables and (iv) An in-vivo evaluation of the effect of P. concavorugulosum-2 and various rhizosphere conditions against F. oxysporum f.sp. radicis lycopersici (FORL) on S. lycopersicum. This was carried out to determine the myco-suppressiveness of the local and well-adapted Penicillium species and Aspergillus sp. against F. oxysporum f.sp. radicis lycopersici (FORL). Five fungal species were isolated from cultivated soils by use of the serial dilution method. The isolates were morphologically identified to genus level using colony characteristics, i.e. conidia, hyphal form, and conidiophores. Molecular identification was carried out to identify the isolates to species level by use of the PCR method. To investigate the dual anti-fungal association, an in-vitro analysis was carried out by use of mycelial disc method. Safety of these isolates on the commonly grown vegetables viz. Spinacia oleracea, Beta vulgaris and Solanum lycopersicum was assessed by inoculating them with respective fungal isolates. Furthermore, in -vivo evaluation was carried out by assessing the effect of the promising isolate; P. concavorugulosum-2 under five (5) rhizosphere amended conditions. The identification of the fungal soil isolates resulted in the confirmation of the isolate identities to be as follows: Penicillium commune-1 (MK660351.1), Penicillium commune-2 (MK660335.1), Aspergillus fumigatus (MN178806.1), Penicillium concavorugulosum-1 (MK841454.1) and Penicillium concavorugulosum-2 (MK841454.1). Analysis of their dual interaction showed the occurrence of various relationships such as antibiosis, competition and mycoparasitism. High inhibition effect of P. concavorugulosum-2 (67.9%) and A. fumigatus (65.36%) on F. oxysporum f.sp. radicis lycopersici (FORL) was noted. A strong positive linear relationship (r = 0.785) was exhibited between P. commune-1 and F. oxysporum f.sp. radicis lycopersici (FORL). Their effect on the bio-safety study on selected vegetables showed that the treatments had statistically significant differences in their effect on the germination, radicle and plumule growth of S. oleracea and B. vulgaris (P<0.05). There was, however, a relatively non-significant positive response on S. lycopersicum. Of interest, is the germination of S. lycopersicum seeds that were treated with P. concavorugulosum-2, P. commune-2 and control which all resulted in 100% germination. In an in-vivo study where the effect of P. concavorugulosum-2 under different rhizosphere conditions was analyzed, there were statistically significant differences in the seedling biomass for the different treatments (P<0.05). The development of P. concavorugulosum-2 as a potential bio-control agent is recommended as it exhibited plant growth stimulatory and protective properties against F. oxysporum. It is recommended that P. concavorugulosum-2 be studied under a situation where it is combined with other promising isolates to explore possible synergistic effects.