Chitosan Increases Tomato Root Colonization by Pochonia chlamydosporia and Their Combination Reduces Root-Knot Nematode Damage

Abstract

The use of biological control agents could be a non-chemical alternative for management of Meloidogyne spp. [root-knot nematodes (RKN)], the most damaging plant-parasitic nematodes for horticultural crops worldwide. Pochonia chlamydosporia is a fungal parasite of RKN eggs that can colonize endophytically roots of several cultivated plant species, but in field applications the fungus shows a low persistence and efficiency in RKN management. The combined use of P. chlamydosporia with an enhancer could help its ability to develop in soil and colonize roots, thereby increasing its efficiency against nematodes. Previous work has shown that chitosan enhances P. chlamydosporia sporulation and production of extracellular enzymes, as well as nematode egg parasitism in laboratory bioassays. This work shows that chitosan at low concentrations (up to 0.1 mg ml-1) do not affect the viability and germination of P. chlamydosporia chlamydospores and improves mycelial growth respect to treatments without chitosan. Tomato plants irrigated with chitosan (same dose limit) increased root weight and length after 30 days. Chitosan irrigation increased dry shoot and fresh root weight of tomato plants inoculated with Meloidogyne javanica, root length when they were inoculated with P. chlamydosporia, and dry shoot weight of plants inoculated with both P. chlamydosporia and M. javanica. Chitosan irrigation significantly enhanced root colonization by P. chlamydosporia, but neither nematode infection per plant nor fungal egg parasitism was affected. Tomato plants cultivated in a mid-suppressive (29.3 ± 4.7% RKN egg infection) non-sterilized clay loam soil and irrigated with chitosan had enhanced shoot growth, reduced RKN multiplication, and disease severity. Chitosan irrigation in a highly suppressive (73.7 ± 2.6% RKN egg infection) sterilized-sandy loam soil reduced RKN multiplication in tomato. However, chitosan did not affect disease severity or plant growth irrespective of soil sterilization. Chitosan, at an adequate dose, can be a potential tool for sustainable management of RKN.

Induction of auxin biosynthesis and WOX5 repression mediate changes in root development in Arabidopsis exposed to chitosan

“…However, recent studies have analysed the effect of chitosan applied in the rhizosphere in order to improve plant yield and to enhance virulence of biocontrol fungi such as P . chlamydosporia 24 , 35 , 36 . In our study we use Arabidopsis to understand the mechanisms underlying the activity of chitosan on root growth.…”

Plants and Associated Soil Microbiota Cooperatively Suppress Plant-Parasitic Nematodes

“…Chitinases could have an effect on egg viability and hatching (Chen and Peng, 2019). Further, the chitinasegenerated chitooligosaccharides could induce the expression of parasitism-related genes in egg-parasitizing fungi (Escudero et al, 2016) inhabiting the cysts (Hu et al, , 2020. Thus, microbiota directly associated with PPN stages in suppressive soils showcasing the ability of nematode suppression elucidate the potential role of diverse microbial consortia in this enticing microbiological milieu.…”

The Multifunctional Role of Chitosan in Horticultural Crops; A Review

“…Therefore, biodegradable biofertilizers, like chitosan, are attracting the research community to avoid the hazards of using inorganic fertilizers. Chitosan gets degraded enzymatically without affecting the soil-borne beneficial rhizosphere biota at low concentrations, and also induces the symbiotic exchange between plant and microbes [ 73 ]. In addition, chitosan is a polysaccharide-based biopolymer, which stimulates the activity of plant symbiotic microbes, resulting in the alteration of rhizosphere microbial equilibrium, thus disadvantaging the plant pathogens [ 173 , 174 ].…”

“…Likewise, NPKB bio-fertilizer mixed with the chitosan-containing fungi Cunninghamella elegans produced NPKP influenced melon plant growth positively and also improved NPK uptake [ 182 ]. Furthermore, tomato plants irrigated with chitosan exhibited decreased multiplication of root-knot nematodes and Pochonia chlamydosporia (a parasitic fungi), resulting in improved root length, weight, and increase shoot growth (Nuria Escudero et al, 2017) [ 73 ]. Furthermore, Ornithogalum saundersiae bulbs coated with chitosan produced earlier flowers and had broader leaves (Salachna et al, 2015) [ 183 ].…”