Protective effect of organic substrates against soil-borne pathogens in soilless cucumber crops

Abstract

Protective effect of organic substrates against soil-borne pathogens in soilless cucumber crops. Scientia Horticulturae, Elsevier, 2016, 206, pp.62-70. 10.1016/j.scienta.2016.04.035. hal-01523673 Scientia Horticulturae 206 (2016 Contents lists available at ScienceDirect Scientia Horticulturae j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i h o r t i a b s t r a c tThe development of sustainable crop protection is expected by vegetable producers and highly encouraged by authorities. For crops grown in soilless systems, vegetable fibers are relevant for both agronomical and plant protection purposes. This work examines their potential against the soil-borne pathogen Fusarium oxysporum f. sp. radicis-cucumerinum. Wood fiber, coir fiber and peat were tested over two cucumber cropping periods. Fusarium blight symptoms were monitored on cucumber, and fungal community structure (PCR-TTGE) in substrates. Substrate sterilization and bio-augmentation with antagonistic strains were also studied; they did not modify protection. Compared to the other substrates, wood fiber increased protection at the end of the first assay, but did not during the second assay. Differences in crop season and plant density may have impacted on cucumber physiology and may have indirectly modified rhizosphere fungal community structure.The sole determination of microbial activity in substrates is not sufficient to predict protection. Growth conditions, substrate type and the microbiome altogether impacted on the protection of cucumber.

Growing Medium Type Affects Organic Fertilizer Mineralization and CNPS Microbial Enzyme Activities

“…Nitrogen (N) is first released as ammonium (i.e., NH 4 + -N or ammonia NH 3 -N whether pH above 8); then, it is converted to nitrite (i.e., NO 2 − -N) by N-ammonium-oxidizing bacteria (AOB) or archaea (AOA) [13] and then converted in nitrate (i.e., NO 3 − -N) by nitrite-oxidizing bacteria (NOB) through nitrification [14,15]. Microbial functions of GM types received little attention in the past [2] and mainly concerned weed and pathogen controls [16,17], biological stability, nutrient immobilization [2,8], nitrification stimulated by urea or ammonium-based fertilization [11], and more recently, regarding nutrient availability [18] and the potential mitigation of greenhouse gas emission by adding biochars [19]. The instability of GM related to carbon (C) cycle was studied through the loss of organic matter [20], dioxygen and carbon dioxide evolution [21][22][23][24][25], or dehydrogenase activity [26] as indicators of global microbial activity.…”

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“…The planting medium used is cocopeat. According to [16], isolated fungal pathogens grown on cocopeat medium to test their survivability on the medium have positive growth on cocopeat indicating that cocopeat is a suitable medium to host both pathogens.…”

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