012 Inhibition of Phytophthora megasperma in Coconut Coir-based Root Substrates

Abstract

<jats:p><jats:italic>Glycine max</jats:italic> (soybean) seed were sown in root substrates composed of 80:0:20 or 0:80:20 coconut coir dust (coir):Sphagnum peat (peat):perlite (v/v) amended with dolomitic limestone to a pH of 5.5. Substrates were inoculated with <jats:italic>Phytophthora megasperma</jats:italic> races 5 and 25 isolated from soybean and grown in dilute liquid V-8 cultures. Uninoculated controls were included. Containers were watered daily to maintain moisture levels at or near container capacity. The experiment was repeated twice. Plants grown in peat-based root substrates inoculated with <jats:italic>P. megasperma</jats:italic> suffered 50% to 100% mortality. No plants in coir-based root substrates displayed visually apparent infection symptoms. Soybean seed were also sown in root substrates that contained 0:80:20, 20:60:20, 40:40:20, 60:20:20 or 80:0:20 coir:peat:perlite (v/v). Inoculum of <jats:italic>P. megasperma</jats:italic> races 1, 5, and 25 was grown on water agar and diluted in deionized water. Solution containing 20,000 colony-forming units (oospores) was mixed into the root substrate of each container. Uninoculated controls were included. As the proportion of coir in the substrate increased, the mortality, the number of plants displaying disease symptoms and the severity of disease symptoms decreased. Plants grown in substrates containing at least 60% coir displayed no visually evident disease symptoms.</jats:p>

In Vitro Suppression of Soilborne Plant Pathogens by Coir

“…Our study complements the study of Candole and Evans (2004) by demonstrating in vitro that coir can suppress soilborne plant pathogens and that this suppression is largely due to microorganisms associated with the substrate.…”

“…w Fisher's least significant difference at P = 0.05. reticulisporum, and several Penicillium species (Waller et al, 2008). Candole and Evans (2004) demonstrated that when tomato seedlings were grown in coir, the incidence of damping off was reduced by 88%, 90%, and 41% for P. capsici, P. nicotianae, and P. aphanidermatum, respectively, compared with peat.…”

“…In the same study, damping-off incidence was reduced by 88%, 90%, and 41% for P. capsici, P. nicotianae, and P. aphanidermatum, respectively (Candole and Evans, 2004). Research has not been done to determine what causes coir to suppress plant pathogens.…”

“…Qualities of coir that make it a good peat substitute include high water holding capacity, excellent drainage, physical resilience, and the fact that it is a renewable resource (Masago et al, 1977;Meerow, 1994;Prasad, 1997). It has been demonstrated that coir can suppress certain soilborne plant pathogens (Candole and Evans, 2004;van der Gaag and Wever, 2005). Combining the diseasesuppressive properties of coir with other management strategies such as fungicide application in an integrated pest management program may result in more effective and less costly management of soilborne diseases in greenhouse and nursery production.…”