Aims The goal of this study was to identify the induced resistance pathway mediated by biochar in the tomatoBotrytis cinerea pathosystem. Methods Tomato wild types and mutants modified in their salicylic acid (SA), ethylene (ET) or jasmonic acid (JA) metabolism were grown in a potting medium amended with biochar produced at 450ºC from greenhouse wastes, to identify the possible pathway(s) involved in biochar-mediated resistance to B. cinerea.Early cellular response of H 2 O 2 accumulation was biochemically tested, and the transcriptional changes of 12 defense-related genes upon B. cinerea challenge of detached leaflets were analyzed. Results Biochar amendment resulted in about 50 % reduction in B. cinerea disease severity in all tested genotypes with the exception of a JA deficient mutant, def1. Biochar amendment induced priming of early as well as late-acting defense responses particularly in the genes Pti5 (ET-related) and Pi2 (JA-related), which are known to be crucial in resistance against B. cinerea. Stronger and earlier H 2 O 2 accumulation subsequent to B. cinerea inoculation in all genotypes was observed as a result of biochar amendment, with the exception of the def1 mutation. Conclusion Biochar-mediated IR in the B. cinerea-tomato pathosystem involves the JA pathway.

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Gray mold (Botrytis cinerea) is an important disease of tomato (Solanum lycopersicum). This study examined defense-related gene expression involved in the resistance to B. cinerea that is induced in tomato plants by benzothiadiazole and Trichoderma harzianum T39 soil drench. In whole plants, transcriptional changes related to salicylic acid and ethylene were induced by the application of a 0.01% benzothiadiazole solution, whereas changes related to jasmonic acid were induced by the application of a 0.4% T39 suspension. On detached leaves, soil treatment by T39 led to enhanced resistance to B. cinerea infection that was proportional to the concentration of the T39 suspension. By 5 days after pathogen inoculation, the plants that had received the 0.04% T39 drench exhibited 62% less severe disease than the untreated plants. The 0.4% T39 drench led to an 84% reduction in disease severity. Observations of B. cinerea infection in leaves harvested from plants grown in the treated soils revealed that drenching with a T39 suspension induces systemic resistance against B. cinerea and primes salicylic acid- and ethylene-related gene expression in a manner proportional to the concentration of the biocontrol agent. Benzothiadiazole treatment induced resistance to gray mold independently of salicylic acid and led to strong priming of two genes known to be involved in defense against B. cinerea, Pti5 and PI2.

Powdery mildew of strawberry is caused by the obligate pathogenic fungus Sphaerotheca macularis f. sp. fragariae. The disease affects the leaves, flowers and fruit of this crop. This study examined the effects of different environmental factors on disease cycle components (germination, conidiation and survival) in strawberry to determine which conditions limit the progress of the disease. The optimal environmental conditions for conidial germination and conidial germ tube length ranged between 15 and 25°C with relative humidity (RH) higher than 75%, but less than 98%. High light intensity reduced germination and hyphal growth. The viability of conidia on infected leaves was examined at temperatures ranging from 15 to 35°C at 80-85% RH. Conidia survival declined over time, but a certain percentage of conidia remained active after 5 months incubation. The rate of conidial germination was significantly higher on young leaves than on older leaves. This observation was consistent across all four tested cultivars. Conidiation at 70-75% RH was similar to that at 80-85%, but greater than that at ‡95% RH. The shortest time from inoculation to appearance of the first disease symptoms was 4 days, at 20 and 30°C with RH above 75%. In growth chambers, temperatures of 10 and 30°C, RH above 95%, radiation of 7000 lux and the use of a more tolerant cultivar were all detrimental to disease development. In general, the environmental conditions required for germination and dispersal of powdery mildew are conducive to disease progress under strawberry production conditions in Israel. Furthermore, viability and survival of the pathogen during and between seasons appears to be dependent on asexual inoculum production.