Fusarium wilts are economically important diseases for which there are no effective chemical control measures. However, biological control and fertility management are becoming efficient alternatives for controlling this disease. Growth media formulated with composts that are able to suppress Fusarium wilt of tomato provide a control system that integrates both strategies. The aim of this study was to predict Fusarium wilt suppression of growth media using abiotic and biotic variables. Grape marc compost was the most effective medium used to suppress Fusarium wilt. Cork compost was intermediate, and light peat and expanded vermiculite were the most conducive growth media. The growth media evaluated were in a pH range of 6.26 to 7.97. Both composts had high β-glucosidase activity. When pH and β-glucosidase activity were taken into account as predictive variables, more than 91% of the variation in severity of Fusarium wilt was explained. This relationship illustrates the effect of nutrient availability and the degree of microbiostasis, two key factors in this pathosystem. Microbial populations involved in suppressiveness were cellulolytic and oligotrophic actinomycetes, fungi, and the ratios cellulolytic actinomycetes/cellulolytic bacteria, oligotrophic bacteria/copiotrophic bacteria, and oligotrophic actinomycetes/oligotrophic bacteria. Based on community level physiological profiles, different community structures were evident among growth media evaluated.

Summary: The genes required for host‐specific pathogenicity inFusarium oxysporumcan be acquired through horizontal chromosome transfer (HCT). However, it is unknown if HCT commonly contributes to the diversification of pathotypes. Using comparative genomics and pathogenicity phenotyping, we explored the role of HCT in the evolution ofF. oxysporumf. sp.fragariae, the cause ofFusariumwilt of strawberry, with isolates from four continents. We observed two distinct syndromes: one included chlorosis (‘yellows‐fragariae’) and the other did not (‘wilt‐fragariae’). All yellows‐fragariaeisolates carried a predicted pathogenicity chromosome, ‘chr^Y‐frag’, that was horizontally transferred at least four times. chr^Y‐fragwas associated with virulence on specific cultivars and encoded predicted effectors that were highly upregulated during infection. chr^Y‐fragwas not present in wilt‐fragariae; isolates causing this syndrome evolved pathogenicity independently. All origins ofF. oxysporumf. sp.fragariaeoccurred outside of the host’s native range. Our data support the conclusion that HCT is widespread inF. oxysporum, but pathogenicity can also evolve independently. The absence of chr^Y‐fragin wilt‐fragariaesuggests that multiple, distinct pathogenicity chromosomes can confer the same host specificity. The wild progenitors of cultivated strawberry (Fragaria × ananassa) did not co‐evolve with this pathogen, yet we discovered several sources of genetic resistance.

The behaviour of Fusarium oxysporum f.sp. lycopersici (Fol) and the effectiveness of the microbial control agent Trichoderma asperellum strain T34 were examined in hydroponically grown tomato plants under five ammonium/nitrate ratios. The results showed that disease severity was reduced by the action of T34 under increasing concentrations of ammonia. Furthermore, rhizosphere F. oxysporum populations decreased with T34 application. The presence of T34 augmented leaf nitrogen concentration in treatments infested with Fol. In addition, T34 application reduced iron concentration in tomato leaves at high ammonium/nitrate ratios and reduced the severity of Fusarium wilt at high iron and nitrogen leaf concentrations.