Control, byBrassicaseed pomace combined withPseudomonas boreopolis, of damping-off of watermelon caused byPythiumsp.

Abstract

A total of 57 isolates of fungi, bacteria, and actinomycetes were screened for their ability to degrade the glucosinolate sinigrin. Pseudomonas boreopolis was the most effective among 26 isolates having the capacity to degrade sinigrin. Treatment with ground Brassica seed pomace and Pseudomonas boreopolis resulted in the release of volatile compounds. Gas-chromatography analyses allowed to identify allyl isothiocyanate and 3-butenyl isothiocyanate as the major volatile compounds released from enzymatic hydrolysis of glucosinolates by Pseudomonas boreopolis. These compounds had strong fungicidal activity against Rhizoctonia solani AG-4, Sclerotium rolfsii, Sclerotinia sclerotiorum, Pythium aphanidermatum, and Phytophthora capsici as revealed by reduced mycelial growth. They were also responsible for reducing the survival of zoospores and oospores of P. aphanidermatum. A large-scale greenhouse trial showed that amendment of growth media (Bas Van Buuren medium No. 4, 7mL; soil, 3 g) with 1% (mass fraction) of the ground Brassica seed pomace and Pseudomonas boreopolis (1 × 10 8 to 1.8 × 10 8 cfu/mL) was effective in controlling damping-off of watermelon caused by Pythium sp., resulting in increased production of healthy, marketable seedlings.Résumé : Le potentiel de dégradation de la sinigrine, un glucosinolate, fut testé chez 57 isolats de champignons, bactéries ou actinomycètes. Parmi 26 isolats ayant manifesté une capacité à dégrader la sinigrine, le Pseudomonas boreopolis s'est révélé le plus efficace. Lors de l'addition du Pseudomonas boreopolis au marc de graines de Brassica broyées, des composés volatils furent libérés. Les analyses par chromatographie en phase gazeuse ont montré que l'allylisothiocyanate et le 3-buténylisothiocyanate étaient les principales substances volatiles libérées par l'hydrolyse enzymatique des glucosinolates par le Pseudomonas boreopolis. Ces substances ont affiché une intense activité fongicide contre le Rhizoctonia solani AG-4, le Sclerotium rolfsii, le Sclerotinia sclerotiorum, le Pythium aphanidermatum et le Phytophthora capsici, tel que révélé par la croissance mycélienne réduite. Ces substances ont aussi diminué la survie de zoospores et d'oospores de P. aphanidermatum. Un essai en serre à grande échelle a montré que l'ajout au milieu de croissance (milieu Bas Van Buuren n o 4, 7mL; sol, 3 g) de 1% (fraction massique) de marc de graines de Brassica broyées et du Pseudomonas boreopolis (1 × 10 8 à 1,8 × 10 8 cfu/mL) était efficace à contrer la fonte des semis du melon d'eau causé par le Pythium sp., donnant ainsi une plus grande production de semis commercialisables sains. Mots clés : marc de graines de Brassica, allylisothiocyanate, 3-buténylisothiocyanate, fonte des semis, melon d'eau, Pythium aphanidermatum, Pseudomonas boreopolis. Chung et al.: damping-off / Pythium sp. / soil amendments / biological control 294

Evaluation of allyl isothiocyanate as a soil fumigant against soil‐borne diseases in commercial tomato (Lycopersicon esculentum Mill.) production in China

“…In our research, laboratory studies and field experiments showed that AITC used as a pre‐plant soil fumigant can effectively control certain soil‐borne bacteria and fungi, nematodes and weeds. AITC is reported to control R. solani , V. dahlia , F. oxysporum , P. aphanidermatum and P. capsica , as also confirmed in our dose–response tests. In addition, we found that AITC has high fumigation biological activity against R. solanacearum , which means that AITC has the potential to control bacterial wilt in the nightshade family.…”

Saprophytic and pathogenic behaviour of R. solani AG2-1 (ZG-5) in a soil amended with Diplotaxis tenuifolia or Brassica nigra manures and incubated at different temperatures and soil water content

“…Olivier et al (1999) found that 2-propenyl ITC was the major compound released by B. nigra with concentrations of 0.4-3.5 mg 2-propenyl ITC g À1 dw of tissue and confirmed its fungicidal activity toward Verticillium dahliae and Helminthosporium solani. 2-propenyl ITC and 3-butenyl ITC are toxic to some fungal plant pathogens, such as R. solani AG4, Sclerotium rolfsii, Sclerotinia sclerotiorum, Pythium aphanidermatum and Phytophthora capsici (Chung et al 2003). In our experiment, the highest concentrations of ITCs extracted from soil occurred in the first few days.…”

The effect of canola (Brassica napus) as a biofumigant on soil microbial communities and plant vitality: a pot study

“…Due to the toxicity of ITCs, it may be used instead of conventional pesticides for the inhibition of soil-borne pathogens (Smith and Kirkegaard 2002). Such pathogens include Verticillium dahliae, Helminthosporium solani, Sclerotium rolfsii, Sclerotinia sclerotiorum and Phytophthora capsici (Chung et al 2003). However, little is known about the effect of biofumigants on the natural soil microbial communities required to maintain soil functions.…”