Viability of dry Trichoderma harzianum spores under storage

Abstract

Spores of the potential biocontrol agent Trichoderma harzianum P1 were prepared without (M1) and with heat shock (40°C for 90 min) after fermentation (M2), filtered into a paste and dried over silica gel. M1 and M2 exhibited high viability (55%) and similar initial trehalose contents (4.0 and 5.4%, respectively) after slow drying. No significant differences in viability were found between treatments during storage for 110 days under different temperatures, T (8, 33 and 42°C) and water activities, a w (0.03, 0.33 and 0.75). Viability of spores, after storage at a w 0:03 were 100 and 70% for 8 and 33°C, respectively. During storage, decrease in trehalose content and viability was faster at a w 0:75 and 42°C. Loss of viability was modeled by a first order kinetic model depending on 1=T and a w . M2 (with heat shock) showed slightly higher trehalose contents than M1 which resulted in 100% viability after 52 days at 8°C. List of symbols a wwater activity , and parameters in GAB equation 1 , and parameters in kinetic equation AV t absolute viability of dried spores after time t AV 0 absolute viability of spores after drying CFU colony forming units k kinetic constant, function of T and a w days )1 k b y c constants in the GAB equation m moisture content g water/g dry spores m 0 monolayer value g water/g dry spores t storage time days TS total number of spores (conidia) V relative viability at certain time t V 0 relative viability at time zero

A novel method to prepare concentrated conidial biomass formulation ofTrichoderma harzianumfor seed application

“…Trichoderma produces spores, which are quite resistant to hostile environmental conditions such as heat, dryness, unfavourable pH or nutrient conditions. Use of the spores arising from the aerial conidiophores produced on substrate surface of PDA plates in the present study is justified and supported by earlier reports of aerial and dried spores being more resistant to stress and have improved shelf life than submerged cultures (Munoz et al1995;Aguilera 1997;Nagayama et al 2007). Nagayama et al (2007) have shown that submerged spores had some common properties with aerial spores, but differed in surface topology and internal organization making aerial spores maintain high viability under dry storage conditions retaining its biocontrol activity, whereas the viability of submerged spores was found to be reduced.…”

“…Besides, during dehydration there is an inherent loss of viability owing to damage in cell membranes and alterations in the DNA or RNA and intracellular proteins (Lievense and van't Riet 1993). The shelf life of dried spores of T. harzianum has been shown to be extended considerably by storage in sealed containers at low moisture contents, for example less than 4% (Pedreschi and Aguilera 1997;Pomella et al 2007). The method described in this work provides flexibility to adjust moisture content not by dehydrating but by addition of moisture.…”

Formulations for delivering Trichoderma atroviridae spores as seed coatings, effects of temperature and relative humidity on storage stability

“…Equally, our findings that spore survival over time is decreased by high temperatures and high humidities are also as predicted as higher temperatures have been shown to lower viability of Trichoderma spp. spores (Pedreschi and Aguilera 1997;Fern andez-Sandoval et al 2012). However, what our data show clearly for the first time, is that the effects of formulation, temperature and RH interact, suggesting that there is not one formulation suitable for storage under all conditions, and particularly that changes in RH affect spore survival in some formula-tions much more than others.…”

“…Equally, our findings that spore survival over time is decreased by high temperatures and high humidities are also as predicted as higher temperatures have been shown to lower viability of Trichoderma spp. spores (Pedreschi and Aguilera ; Fernández‐Sandoval et al . ).…”

Induction of trehalose in spores of the biocontrol agent Trichoderma harzianum

“…Figure 3 shows that trehalose continuously increased from an initial content of 2.3 to 4.5% (d.w.) during conditioning of the paste of spores at Aw 0.97 after 72 h. It is unknown if further conditioning would have increased this value further. However, studies on spore viability under storage indicated that trehalose content and viability decreased considerably after long times at high HR [21]. Direct transfer to Aw 0.03 produced a slight reduction in spore viability in comparison with fast and slow drying procedures with conditioning at Aw 0.97 (43.6% vs. mean values of 52% and 58%, respectively) in spite of a much lower initial trehalose content.…”