Association of oilseed rape cultivars (Brassica napus L.) with fungal endophyte of Pseudogymnoascus pannorum

Introduction:
Microorganisms that live inside plant tissues, termed endophytes, may offer benefits to their host affected to biotic and abiotic stress conditions including extreme temperatures (Card et al., 2016). Characterized endophytic strains which show no host specificity could be transferred from their original wild plant hosts into elite cultivars through different method of inoculation.
Fungal endophyte of Pseudogymnoascus pannorum. is a psychotolerant fungus resistance to frosting temperature and associated with plants grown in the arctic regions. The association of a strain of Pseudogymnoascus pannorum which has been previously isolated from a wild turnip was investigated with five oilseed rape hybrids in this study (Roodi, 2019).
Material and methods:
Seeds of five oilseed rape hybrids were surface-disinfected and inoculated by immersing in spore suspension of the fungus. Seeds were then transferred to pots and placed in a glasshouse in a completely randomized block design with three replications. The colonization frequencies of brassica seedlings inoculated with fungal endophyte was assessed at two vegetative plant growth stages. This was done by plating the 15 small piece of disinfected tissue of stem of each hybrids in a Perti dish with Potato Dextrose Agar medium. Petri plates were incubated at 22˚C and checked regularly for microbial growth. The colonization tissue frequency of each hybrid calculated and data statically analysed. The penetration of fungal hyphae was also studied by a light microscope.
Results and discussion:
The results from re-isolation of fungal endophyte from inoculated oilseed rape hybrids demonstrated that the fungal endophyte of Pseudogymnoascus pannorum colonized shoot tissues of all five hybrids studied and establish a close association with all oilseed rape hybrids. The analysis of variance of colonization tissue frequency showed that there is no significant difference between hybrids. The highest and lowest colonization rate was belonging to hybrid Turan and Ladoga with 19.96 and 18.81 percent respectively. The visual observation of inoculated plants showed that the endophytes does not induce any disease symptoms or change in plant growth and development of brassica plants. Control plants were not infected with the fungal endophyte. Although the origin host of the fungal endophyte was a wild turnip of Brassica rapa species, the result from inoculation indicates that this strain shows no host specificity. This is consistence with the result of another study that showed a strain of Beauveria bassiana isolated from another host can colonize other species such as oilseed rape (Vidal & Jaber, 2015). However, there was a significant difference between rates of colonization at two different growth stages. The mean colonization frequency at one and three-leaf stage was statically compared with t-student (unpaired group) witch was significantly different (99%). The mean colonization rate of hybrids was 17.77 and 20.48 percent at one and three-leaf stage respectively. Microscopic study of stem tissues also illustrated that the hyphae of fungus penetrate inside the epidermal layer of stem tissue.
Conclusion:
In this study we demonstrated that a specific strain of Pseudogymnoascus pannorum is able to colonize the areal parts of oilseed rape hybrids and establish a close association. This genus of fungus is an endophyte with psychotolerant properties that occupies plant grown in arctic regions. The results from this study can be used for further investigations on symbiosis benefits of this association especially to study the induction of resistance of oilseed rape to environmental stresses such as frosting and plant growth enhancement.
Acknowledgment:
This study was supported by Agricultural Research, Education and Extension Organization of Iran, Massey University and AgResearch Ltd. (Grasslands campus), Grasslanz Technology and Ellet Trust foundation, New Zealand.
Keywords:
Key words: Canola, seed inoculation, endophytic association, host specificity
References:
1- Card SD, Hume DE, Roodi D, McGill CR, Millner JP & Johnson RD (2015) Beneficial endophytic microorganisms of Brassica – A review. Biol Control 90: 102-112.
2- Roodi D, Millner JP, McGill CR, Johnson RD & Card SD (2019) Bio-prospecting of endophytes of Brassica. PhD dessertation. Faculty of plant science, Massey University. Palmerston North. New Zealand. Pp.161.
3- Vidal S & Jaber LR (2015) Entomopathogenic fungi as endophytes: plant-endophyte-herbivore interactions and prospects for use in biological control. Curr Sci 45-54.