Cecilia Abramoff

Biological control of Botrytis cinerea on tomato using naturally occurring fungal antagonists

Abstract In order to evaluate the potential of naturally occurring filamentous fungi having potential as biocontrol agents effective against grey mould and post-harvest fruit rot caused by Botrytis cinerea on tomato, fungal saprophytes were isolated. They were obtained from leaves, fruits and flowers belonging to different species of cultivated and spontaneous Solanaceous plants collected at the horticultural area of La Plata, Argentina. Of 300 isolates screened for inhibition of B. cinerea using the dual culture technique on agar plate, 12 strains inhibited strongly mycelial growth of the pathogen. Among the antagonists one isolate of Epicoccun nigrum (126), four of Trichoderma harzianum (110, 118, 248 and 252) and four isolates of Fusarium spp. decreased the spore germination of B. cinerea between 30 and 70%. These isolates were probed on tomato fruits to evaluate their biocontrol activity against post-harvest grey mould. In growth chamber tests, E. nigrum (27), F. equiseti (22, 105) and T. harzianum (118, 252) reduced the diameter of fruit lesions by 50 – 90% and were selected for further biocontrol assays of tomato plants in the greenhouse. Although there were not significant differences between the treatments and the control, F. equiseti (105), E. nigrum (27) and T. harzianum (118) reduced by 20, 22 and 22 respectively the disease on whole plants. The targeted application of isolates of E. nigrum, T. harzianum and F. equiseti provides a promising alternative to the use of fungicide spray to control B. cinerea on tomatoes.

Biological control of leaf grey mould of greenhouse tomatoes caused by Botrytis cinerea

Botrytis cinerea (grey mould) is one of the most common diseases of glasshouse crops and is a major cause of plant death in long-season tomato production. A disease management field trial was conducted in a commercial tomato production greenhouse for comparison of seven fungal antagonists which had previously exhibited potential as biological control agents with respect to Botrytis cinerea incidence and severity. Isolates of Trichoderma harzianum, Candida pelliculosa, Rhodotorula rubra, and Fusarium semitectum were recovered from leaves, fruits and flowers of different solanaceous plants. The fungal antagonists were tested for their control of leaf grey mould on tomato under greenhouse conditions during 2008 and 2009. In both years, foliar spray with strains of Trichoderma harzianum and Fusarium semitectum suppressed the foliar infection of B. cinerea. The suspensions of T. harzianum 118 and 252 and F. semitectum 25 significantly reduced disease incidence (65–95%) and severity (50–77%) in inoculated plants compared to untreated controls (P ≤ 0.05). Our results suggest that formulations of saprophytic fungi selected from the naturally occurring mycoflora could be an effective tool in the biological control of tomato grey mould.

Suppression of seed-borne Alternaria arborescens and growth enhancement of wheat with biorational fungicides

ABSTRACT Alternaria spp. are among the major fungal contaminants of wheat grain under postharvest and storage conditions, where A. arborescens was recently detected as a new member of this complex in Argentina causing black point. The aim of this study was to assess the potential of some biorational agents to control A. arborescens and their plant growth promoting of wheat. Seed treatments with spore suspensions of Trichoderma harzianum and Eppicoccum nigrum, extracts from Lippia alba and garlic, sodium bicarbonate, salicylic acid (SA), potassium chloride and dibasic sodium phosphate (SP) were applied to grains of wheat cultivar BIOINTA 1004 before their inoculation with the pathogen. After 7 days, seed germination and infection, necrotic symptoms on emerged seedlings and fresh weight were evaluated. Remarkable results were obtained with L. alba, SA and SP treatments that reduced symptoms markedly compared with the control. Interestingly, necrosis of radicles was significantly reduced by the application of all treatments tested. Moreover, fresh weight of seedlings was significantly increased with the application of the two antagonists, diluted garlic juice and the three tested salts in comparison with controls. Therefore, a positive role as growth promoters can be elucidated. It is concluded that compounds here tested have potential as ecofriendly alternatives to control seed-borne Alternaria fungi of wheat.