Treatments with conidia of Penicillium oxalicum produced in a solid‐state fermentation system were applied at similar densities (6 × 106 spores/g seedbed substrate) to tomato seedbeds in water suspensions (T1: 5 days before sowing, or T2: 7 days before transplanting; 15 days after sowing), or in mixture with the production substrate (T3: 7 days before transplanting; 15 days after sowing). Treatments T2 and T3 significantly (P = 0.05) reduced fusarium wilt of tomato in both greenhouse (artificial inoculation) (33 and 28%, respectively) and field conditions (naturally infested soils) (51 and 72%, respectively), while treatment T1 was efficient only in greenhouse (52%). Verticillium wilt disease reduction was obtained with T3 in two field experiments (56 and 46%, respectively), while T1 and T2 reduced disease only in one field experiment (52% for both T1 and T2). Treatment with conidia of P. oxalicum plus fermentation substrate (T3) resulted in better establishment of a stable and effective population of P. oxalicum in seedbed soil and rhizosphere providing populations of approx. 107 CFU/g soil before transplanting. Results indicate that it will be necessary to apply P. oxalicum at a rate of approx. 106–107 CFU/g in seedbed substrate and rhizosphere before transplanting for effective control of fusarium and verticillium wilt of tomato, and that formulation of P. oxalicum has a substantial influence on its efficacy.

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Sugars, polyalcohols, inorganic salts, and detergents were added to conidia of Penicillium oxalicum at three different points of the production-formulation process to improve water dispersal. Effects also were tested on conidial germination and production. Conidial germination without additives ranged from 51 to 79%. Additives did not reduce conidial germination except for 50% polyethylene glycol (PEG) 300 and 10% CaCl2. Sunflower oil and sodium alginate, sucrose (0.5, 15, 30, and 60%), D-sorbitol (30 and 60%), glycerol (2, 5, 20, and 30%), 30% PEG 300, CaCl2 (0.01 to 1%), Tween 20 (0.01, 0.02, 0.5, and 1%), and Tween 80 (0.01 to 1%) enhanced conidial germination. Production without additives ranged from 0.57 to 4.58 conidia × 108 g-1 substrate. Additives did not affect conidial production except for reduction by 60% D-sorbitol, 60% fructose, and 10% CaCl2. Conidial dispersal in water improved when 1.5% sodium alginate was added to substrate in bags before production, and when 1.5% sodium alginate, 60% sucrose, 60% D-sorbitol, 60% fructose, 5 to 20% PEG 8000, or 20% glycerol were added to conidia before drying. Dispersal of dried conidia was enhanced with 1% Tween 20, 1% Tween 80, 1% Trition X-100, 10% Agral, and 1.5% sunflower oil. Two P. oxalicum formulations (conidial suspensions maintained with 60% sucrose or 1.5% sodium alginate for 10 min before drying) significantly reduced tomato wilt caused by Fusarium spp. under greenhouse conditions and, in a preliminary trial, by Verticillium spp. in a field assay.

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Comparative studies in Xanthomonas have provided a vast amount of data that enabled to deepen in the knowledge of those factors associated with virulence and Xanthomonas plant interaction. The species of this genus present a wide range of host plants and a large number of studies have been focused to elucidate which mechanism are involved in this characteristic. In this study, comparative genomic and phenotypic analysis were performed between X . citri subsp. citri ( Xcc ), one of the most studied pathogens within Xanthomonas , and X . arboricola pv. pruni ( Xap ), a pathogen which has aroused great interest in recent time. The work was aimed to find those elements that contribute to their host divergence despite the convergence in the symptoms that each species cause on Citrus spp. and Prunus spp., respectively. This study reveals a set of genes that could be putatively associated with the adaptation of these pathogens to their hosts, being the most remarkable those involved in environmental sensing systems such as the case of the TonB-dependent transporters, the sensors of the two-component system and the methyl accepting chemotaxis proteins. Other important variants were found in processes related to the decomposition of the cell wall as could be appreciated by their dissimilar set of cell-wall degrading enzymes. Type three effectors, as one of the most important factors in delineating the host specificity in Xanthomonas , also showed a different array when comparing both species, being some of them unique to each pathogen. On the other hand, only small variations could be connected to other features such as the motility appendages and surface adhesion proteins, but these differences were accompanied by a dissimilar capacity to attach on host and non-host leaf surface. The molecular factors found in this work provide the basis to perform a more in-depth functional analyses that unveil those actual factors associated with pathogenesis and host specificity in Xcc and Xap .

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