THE EFFECTS OF VERMICOMPOST MIXED WITH TRICHODERMA ASPERELLUM ON THE GROWTH AND PYTHIUM ROOT ROT OF LETTUCES

Abstract

Vermicompost products are efficient organic fertilizers. Therefore, vermicompost fortified
with a biocontrol agent may have the potential to improve plant growth and also suppress plant disease. In
this research, planting substrates (chopped coconut husk: coir dust; 50:30 % by volume) supplemented with
vermicompost (VC) (20 % by volume) or VC fortified with Trichoderma asperellum CB-Pin-01 (VCT) (20
% by volume) were evaluated for the effects on lettuce growth and root rot caused by Pythium
aphanidermatum (Pa). The 14-day-old lettuce (Butter Head) seedlings grown in a sowing substrate (perlite:
vermiculite; 2:1 V/V) were transplanted into a 6-inch plastic pot containing prepared substrates. A plant
nutrient solution with an electrical conductivity (EC) of 1.6 mS/cm and a pH of 5.5-6.0 was applied weekly
to the substrate at 200 ml/pot. Results revealed that both VC and VCT increased plant growth after planting
for 42 days as compared to a control (substrate without vermicompost). However, a substrate containing
VCT significantly increased the height, leaf number, leaf area, basal stem cutting surface area, and plant fresh
and dry weights when compared with the control. When the substrates were inoculated with Pa, the VCT
(+Pa) treatment increased the height, leaf number, leaf area, basal stem cutting surface area, and plant fresh
and dry weights when compared with a Pythium treated control (VC(+Pa)). After lettuce harvesting, T.
asperellum CB-Pin-01 could be completely recovered from the planting substrate (100%) and the lettuce root
(100%), while this fungus helped reduce substrate and lettuce root colonization by Pa when compared with a
control (VC(+Pa)).