Trichoderma spp. and a carob (Ceratonia siliqua) galactomannan to control the root-knot nematode Meloidogyne incognita on tomato plants

Restrictions about the use of chemicals have limited the availability of control measures against plant-parasitic nematodes. The search for more sustainable approaches has focused the attention on biological control agents, such as Trichoderma species. In recent years, there has been a growing interest in the use of biopolymers for a wide range of applications. These polysaccharide-based compounds may be 20 good carriers of microbial agents or act as barriers against pathogens or pests for their ability to form coating films. In this study, we evaluated the combination of a biopolymer obtained from the leguminous plant Ceratonia siliqua and T. harzianum M10, T. atroviride P1 or T. longibrachiatum MK1, as root protector or adjuvant agents, for the management of the root-knot nematode Meloidogyne incognita. Coating tomato roots with the carob galactomannan biopolymer followed by soil application of selected Trichoderma strains reduced the root galling index caused by M. incognita and soil nematode population in comparison to untreated control under greenhouse conditions. 25 Scanning electron microscopy revealed that coated tomato roots were embedded within a polymeric material. The sedimentation test showed that the addition of this biopolymer retarded the tendency of Trichoderma spores to settle in the bottom of aqueous suspension. In conclusion, beneficial fungi combined or formulated with a biopolymer could represent a promising strategy to increase their activity in plant protection and enhance their proliferation or distribution into rhizosphere.