Effect of temperature on mycelial growth of Trichoderma, Sclerotinia minor and S. sclerotiorum, as well as on mycoparasitism

Abstract

Environmental conditions are very important for the biological control of plant diseases. In a previous study, isolates of Trichoderma asperellum (IBLF 897, IBLF 904 and IBLF 914) and T. asperelloides (IBLF 908) were selected as antagonists of S. minor and S. sclerotiorum, causal agents of lettuce drop, one of the most relevant diseases affecting the lettuce crop. In this subsequent study, the mycelial growth of these isolates and pathogens, as well as the mycoparasitism of isolate IBLF 914, was evaluated at different temperatures. The mycelial growth of the isolates of T. asperellum and T. asperelloides, as well as of S. minor and S. sclerotiorum, was evaluated at temperatures ranging from 7 to 42 o C. ABSTRACT32 o C, in gerboxes containing substrate. S. minor and S. sclerotiorum showed mycelial growth at temperatures ranging from 7 to 27°C, but no growth occurred at 32 °C, and both pathogens had greater mycelial growth at 22°C. The isolates of Trichoderma grew at temperatures ranging from 12 to 37°C, with maximum growth at 27°C. The isolate IBLF 914 had mycoparasitism and reduced the disease in lettuce seedlings at temperatures ranging from 22 to 32°C. Since lettuce drop occurs when mild temperatures and high humidity prevail and the antagonist was more effective at higher temperatures, it is recommended that Trichoderma is applied in lettuce fields in Brazil also during warmer months of the year to reduce the inoculum remaining in the soil before planting the winter crop, which is more affected by the disease. v.42, n.3, p.222-227, 2016. 22, 27 e 32 o C em caixas gerbox contendo substrato. S. minor e S. sclerotiorum apresentaram crescimento micelial nas temperaturas de 7 a 27 °C, mas não cresceram a 32 °C e ambos os patógenos apresentaram maior crescimento micelial a 22 °C. Os isolados de Trichoderma cresceram em temperaturas entre 12 e 37°C, com um máximo a 27 o C. O isolado IBLF 914 exibiu micoparasitismo e reduziu a doença nas plântulas de alface em temperaturas entre 22 e 32°C. Como a murcha de esclerotínia ocorre quando predominam temperaturas amenas e elevada umidade e o antagonista foi mais efetivo em temperaturas médias a elevadas, sugere-se que Trichoderma seja aplicado em lavouras de alface no Brasil também nos meses mais quentes do ano visando a reduzir o inóculo presente no solo antes da instalação da cultura de inverno, mais afetada pela doença. RESUMOPalavras-chave: murcha de esclerotínia, Lactuca sativa, Trichoderma asperellum, Trichoderma asperelloides, controle biológico.One of the most important diseases affecting lettuce is lettuce drop, caused by Sclerotinia minor and S. sclerotiorum (8, 9). This disease is favored by mild temperatures and high humidity (11). Managing lettuce drop is complex and involves integrating fungicide applications with several other control methods such as deep plowing, roughing, crop rotation and subsurface-drip irrigation (12

Phylogenetic Diversity of Trichoderma Strains and Their Antagonistic Potential against Soil-Borne Pathogens under Stress Conditions

“…Similar results by another group [ 75 ] proved that 25 °C promotes more mycelial growth of T. harzianum than 15 °C. Another group, Ref [ 19 ] observed an increase in the mycelial growth of all Trichoderma isolates at temperatures ranging from 12 ºC to 27 ºC, and then decreased up to 37 ºC, being inhibited at 42 ºC.…”

“…Trichoderma strains use several modes of action, including acidification, chelation, reduction, and hydrolysis to regulate the availability of metals such as phosphate and iron solubilization. Although Trichoderma can live under different environmental conditions, temperature plays a substantial function in enhancing its growth and mycoparasitic activity [ 18 , 19 , 20 ]. The harmful pathogenic fungi that Trichoderma can inhibit include, Fusarium solani [ 21 ], F. graminearum [ 22 ], and Macrophomina phaseolina [ 23 ].…”

Colonization of Vitis vinifera L. by the Endophyte Trichoderma sp. Strain T154: Biocontrol Activity Against Phaeoacremonium minimum

“…at 6 and 12 weeks post-inoculation, secateurs were cleaned with Incidin ™ (Ecolab, UK) and used to cut plants up to 15 cm above the inoculation point. All samples with different treatments were then kept in sterile paper bags at 4°C to avoid fungal growth (Mukherjee et al, 2013;Domingues et al, 2016). Samples were then prepared for analyzing the inoculation point by dividing the samples in small parts (technical replicates) (Supplementary Data S2, Figure S4).…”

Effect of low temperature culture on the biological characteristics and aggressiveness of Sclerotinia sclerotiorum and Sclerotinia minor

“…Sometimes, SWM infected plants caused by S. sclerotiorum were also observed in fields in which SWM was dominantly caused by S. minor, but co-infection by both S. sclerotiorum and S. minor was never encountered. Previous studies showed that mycelial growth of both S. sclerotiorum and S. minor occurred at temperatures ranging from 12°C to 27°C, and sclerotia of S. minor germinated and exhibited mycelial growth at temperatures ranging from 6°C to 30°C, but S. minor shows much more sensitivity to low temperature (Domingues et al, 2016). Based on the low temperatures in summer in the region where we observed SWM caused by S. minor, it was speculated that S. minor is favorised by such low temperature.…”