**2.1. Strains**

endogenous microorganisms with sufficient quality and quantity to their application in the crops areas [1]. In the soil there are microorganisms with antagonistic capacity, the most studied in the world is *Trichoderma* spp [2]; due to its ubiquity, its ability to isolate and present

In the last 10 years, research work has been carried out, and native species of *Trichoderma* spp. have been isolated, selected and evaluated, with the potential to establish a biological control against different diseases, which have proposed several mechanisms of innovation for the implementation of this fungus with satisfactory results [5–7]. These mechanisms of action may act synergistically on various phytopathogens such as *Septoria triticii* in wheat, *Sclerotinia sclerotiorum* in soybean and lettuce, *Rhizoctonia solani* in soybean, *Sclerotium rolfsii* in cucumber

The genus *Trichoderma* presents several mechanisms by which they easily move to the phytopathogen, but the most important is based on three types: (a) Direct competition for space or nutrients [10–13], (b) Production of antibiotic metabolites, whether of a volatile or nonvolatile nature [14, 15] and (c) Direct parasitism of some species of *Trichoderma* spp [16, 17].

The fungus *F. oxysporum* Schlechtend.: Fr. cause root and neck rot in tomato plants (*Lycopersicon esculentum* M.), causing severe losses that affect the quality and quantity of the production [18]. The most noticeable symptoms produced by using *F. oxysporum* occur in the transplantation of seedlings and at the beginning of flowering [18]. If a transverse section of the stem is made, it is possible to observe a vascular necrosis of brown color, particularly on the smaller lateral roots; which accelerates foliage wilting; after the plant dies and the fungus fructifies on the surface of the stem, under conditions of a humid environment [19]. The vascular wilt of the tomato by *F. oxysporum* was first described by Masse in 1885, on the Isle of Wight and Guernsey, located in the English Channel. In the year 1899, the disease was already in the United States of America, causing severe losses in the areas dedicated to growing tomato in the north of the state of Florida. In 1940 they reported that the disease was disseminated

The tomato (*L. esculentum* M.), is grown in all types of soils for family and commercial use [21]; for the 2016 year, occupied the first place with a total area planted of 4734 million hectares with a production of 163 million tons [22]. To date China is the first producer with 50 million tons, followed by India with 18 million tons, the United States with 12 million tons and Mexico is in the tenth position with 3282 million tons [23]. In Mexico the statistics of the Sistema de Información Agropecuaria [24], reported that in the 2016 year, 52,374 thousand hectares of tomato were planted with a production of 2875.164 tons, with a value of 15,735 million of pesos. While data from the Sistema Producto, they indicated that exports amounted to 20 billion pesos, with the United States and Canada being the main buyers; where the main producers were Sinaloa with 867,832.04 tons, San Luis Potosí with 196,011.25 tons and Michoacán with 169,768.98 tons [25]. Tomato production under greenhouse conditions during 2016 represented 26.2% of the national production, with average yields of 171.82 tons/

cohombro, *Fusarium oxysporum* in tomato and *Pythium splendens* in beans [8, 9].

156 Fusarium - Plant Diseases, Pathogen Diversity, Genetic Diversity, Resistance and Molecular Markers

throughout the world and *F. oxysporum* was given greater importance [20].

ha, where Puebla ranked 14th with 75,219.09 tons of tomato [24].

rapid growth on a large number of substrates [3, 4].

Strains native from the state of Puebla-Mexico were used, Th-T4 (3) from *Trichoderma harzianum*, Tav-T7 (2) from *Trichoderma atroviridae*, Tv-T3 (1) from *Trichoderma viridae* and the strain (Fo-A) from *Fusarium oxysporum*, which belong to the Centro de Recursos Genéticos del Centro de Agroecología del Instituto de Ciencias-BUAP and are in culture medium PDA (Potato Dextrose Agar).

#### **2.2. Rate of development and speed of growth**

The rate of development and rate growth of Th-T4 (3), Tav-T7 (2), TV-T3 (1) and (Fo-A) strains, was determined in Petri dishes (4.5 cm in diameter) in culture medium (PDA), incubated at room temperature for 7 days; the growth rate was measured every 24 h until the culmination of the total colonization of the strains, the macroscopic morphological characteristics of the colonies were recorded in texture, density, aerial mycelium and color. The rate of development and growth rate were determined using the following formula [28]:

$$\text{TD} = \text{VCF} - \text{VCI/Number of days} \tag{1}$$
