EFFECT OF CRUDE CULTURE FILTRATES OF THE PATHOGENIC FUNGUS PHOMA MEDICAGINIS ON IN VITRO CULTURES OF PEA

Abstract

Biotic stress is one of the major causes for considerable yield loses and limits in plant performance. To cope with this problem, multidisciplinary approach is applied and research is carried out at several levels of organization of the living organisms. The large scale studies are due to the fact that resistance is a complex of genetic, physiological, biochemical and other mechanisms. It includes plant-pathogen interactions demonstrated on organism, cellular and molecular level. Biotechnology affords an opportunity for application of alternative methods to investigate stress response and to select for higher tolerance. Essential prerequisites for this kind of work are the in vitro culture system and a stress factor which is applicable in vitro and simulates the natural stress factor on cellular or tissue level. In this respect culture filtrates from pathogenic fungus can be used as a selective factor in plant cell in vitro cultures. The objectives of the study were to define the appropriate culture filtrates from a pathogenic fungus which can be used for in vitro modeling of biotic stress using plant tissue cultures. Long-term organogenic pea cultures and crude culture filtrates from the virulent isolate of the pathogenic fungus Phoma medicaginis var. Pinodella causing ascochytosis disease were used. The negative effects of crude culture filtrates obtained at different stages of fungus growth were studied recording changes in pea bud and shoot induction and development. The virulence of the crude culture filtrate was tested after being subjected to cold or hot sterilization. The culture filtrate after the 5th day of fungus suspension initiation demonstrated suppression of the pea organogenesis. The negative effect is strongest on the 9th day of fungus cultivation. The cold sterilization of the fungus filtrate by Millipore filter with 0.2 μ membrane pores is the most effective and reliable. However, it is more difficult compared to autoclaving which is reliable, too, but decreases culture filtrate activity.