**1. Introduction**

Common bean (*Phaseolus vulgaris* L.) is the second major crop in México. In 2016, approximately 1.63 million hectares were cultivated with common beans and an average grain yield

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© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

of 690 kg ha−1 was reported [1]. Grain yields of common bean in México are low since potential yields are estimated to be ≈3 t h−1. Several factors such as biotic (diseases, insect pest, weeds) and abiotic (drought, freeze, low-fertility soils, high temperatures, salinity) stresses reduce common bean production [2]. Drought stress and root rots caused by *Fusarium solani* f. sp. *phaseoli* (FSP), alone or combined, affect bean grain yield in major regions producing common beans in México. Both stresses reduce grain yields due to increase the percentages of seedling death and, consequently, reduce the crop standing (root rots) or reduce growth and development and seed production (water deficits) [3, 4].

Field trials included in this report were conducted in one location of the State of Aguascalientes: Sandovales and one from the State of México: Chapingo. Sandovales is located at 22°09′N, 102°18′W, and 2000 m above sea level and shows dry land conditions with summer rainfall. Annual average precipitations range from 350 to 400 mm, with average temperature ranges from 12 to 18°C. Chapingo is located at 19°28′N, 98°52′W; 2250 m above sea level and has a temperate climate with fresh summer and low variable temperatures (15–18°C) and the

Analysis of *Fusarium*-Common Beans Pathosystem in Aguascalientes, Mexico

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The procedures for *Fusarium* isolates characterization by using *in vitro*, pathogenicity and AFLP genotype strategies were described when we analyzed the isolates from the State of

Previous works indicated us that soils of Chapingo and Sandovales are highly, naturally and homogeneously infested in most cases by FSP [12, 13]. We divided the characterizations into

The first group included 6 (experiment I), 75 (experiment II) and 36 (experiment III) (**Table 1**) common bean genotypes under rainfall conditions at Sandovales, Aguascalientes. Experiments were established on June 27 (E-I and E-II) and July 11 (E-III), 2002 under randomized complete block (RCB) design with four replications (E-I), where experimental unit was three rows 5 m-length. The germplasm of E-II was divided into three groups based on color seed coat: 25 pinto seed-type bean genotypes, 25 Flor de Mayo seed-type and 20 black seed beans. Each group of genotypes was randomized in a RCB design with three replications, and where experimental unit was two rows 6 m-length. Finally, germplasm in E-III was randomized on 6×6 lattice design with three replications and experimental unit of 2

In the second group of experiments, 49 common bean genotypes (**Table 1**) were evaluated under two levels of soil moisture: irrigated and rainfed conditions. Germplasm was randomized in 7 × 7 lattice design with four replications. Two replications were carried out under irrigated conditions, while the other two under rainfed conditions (irrigation was stopped when the most of germplasm initiated flowering and no irrigation was supplied until har-

In both groups of experiments, FSP root rot severity ratings were determined at 28 and 56 days after sowing. Five plants were randomly picked off from each experimental unit and damage was evaluated by using the scale described by Abawi and Pastor-Corrales [6]. The scale has nine degrees of damage (1–9) where 1 = no symptoms and 9 = more than 75% of root or stem tissues infected by the pathogen. We took the values 1–3 as a reaction of resistance, while

vest). Experiments were established in Sandovales and Chapingo, México.

Aguascalientes [11] and Aguascalientes, México, Guanajuato and Veracruz [4].

**2.2. Reactions of common bean germplasm to root rot pathogens under field** 

annual average precipitations range from 600 to 700 mm [10].

**2.1. Variability of FSP isolates from Aguascalientes, México**

**conditions**

two groups.

rows 6 m in length.

Grain yield reductions decrease crop profits. More than 70% of common bean growers use low inputs for production, or in some cases, common bean is a subsistence crop. We consider that production of common bean germplasm with combined resistance to drought stress and diseases could be an appropriate strategy for grain yield improvement because it is a cheap, sustainable and durable strategy for grain yield stabilization [5]. The control of major root rot pathogens includes chemical, cultural and biological strategies, but most of them are not enough efficient to control pathogens or they have poor possibilities to be applied under Mexican bean grower conditions because they are expensive [6].

Mexican common bean breeding programs need the former analysis of plant-pathogen pathosystem to perform the selection of those genotypes with improved resistance to root rot pathogens and the best environmental adaptation. Another challenge is the characterization of pathogenic variability of root rot pathogen populations to identify molecular genetic factors of parasitic capability of the pathogen, since these characteristics affect the variation on reactions of common bean germplasm to the fungus. Then, the development of molecular marker technologies to improve the evaluation and selection of resistant common bean germplasm under marker-assisted selection strategy is needed [7].

This research includes three objectives: (1) to characterize the genetic variability patterns of *Fusarium* isolates from Aguascalientes and other regions of México; (2) to assess the reactions of each root rot pathogen in *Phaseolus* sp. germplasm under field and controlled conditions and (3) to define the genetic basis of resistance to each root rot pathogen in common beans.
