Effect of Farnesol, a compound produced by Trichoderma when growing on bean (Phaseolus vulgaris L.)

Common bean (Phaseolus vulgaris L.) is the third most important food legume crop worldwide, surpassed only by soybean (Glycine max (L.) Merr.) and peanut (Arachis hypogea L.). Trichoderma (Teleomorph: Hypocrea) is a fungal genus that is found in the soil. It is a secondary fast-growing opportunistic invasive organism, which produces enzymes able to degrade the fungal cell wall and induce production of compounds with antimicrobial activity [1]. Farnesol is a signalling molecule for self-regulation that by accumulating in the extracellular space generates a response across local fungal population. The effects of farnesol production by Trichoderma in bean plants are unknown [2]. The objective of this work was to determine the effect of different concentrations of farnesol on the development of bean. Bean seeds were surface-sterilized (1% sodium hypochlorite for 3 min and distilled water for 6 min) and pre-germinated. The plants were grown under controlled conditions in hydroponic culture for 14 days, and the effects of different concentrations of farnesol (10µM, 100µM, 1000µM, 2000µM and 5000µM) in the nutrition solution were evaluated by assessing the wet weight and dry weight of the aerial parts and root systems. The results (Figure 1) showed a negative effect on growth at concentrations of 10µM and 100µM farnesol, which could be related to abscisic acid synthesis. However, with 2000µM of farnesol, bean plants showed increased development of aerial parts and root systems.

Fig. 1: Evaluation of the dry weight (g) of the aerial part and root of bean plants grown for 14 days in conditions in hydroponic culture. Values with different letters are significantly different (Fisher's LSD. p < 0.05).

In conclusion, low concentrations of farnesol cause a reduced development of the root system and aerial part of the plant bean, while a high concentration (2000 uM) increases its development, presenting beneficial effects on the bean plant.

Acknowledgements: The grant awarded to Sara Mayo Prieto (FPU12/00677) by the Ministry of Education, Culture and Sport (Spain) and Ministry of Economy and Competitiveness for National project “Farnesol as self-regulatory molecule in Trichoderma. Tyrosol and farnesol signaling in Trichoderma-bean interaction” (AGL2012 – 40041-C02 – 02). Junta de Castilla y León, for the project “Effect of terpenes and physiologically related compounds produced by Trichoderma parareesei in the development of common bean (Phaseolus vulgaris L.) and in defensive responses of this plant” (LE228U14).

Keywords: Hydroponic culture, dry weight, wet weight, root, shoot.

References:

[1] Mayo S, Gutiérrez S, Malmierca MG, Lorenzana A, Campelo MP, Hermosa R, Casquero PA. Influence of Rhizoctonia solani and Trichoderma spp. in growth of bean (Phaseolus vulgaris L.) and in the induction of plant defense-related genes. Front Plant Sci 2015; 6: 685.

[2] Malmierca MG, Cardoza RE, Alexander NJ, McCormick SP, Collado IG, Hermosa R, Monte E, Gutiérrez S. Relevance of trichothecenes in fungal physiology: Disruption of tri5 in Trichoderma arundinaceum. Fungal Genet Biol 2013; 53: 22 – 33.

No conflict of interest has been declared by the author(s).