5. Data

The basic data types collected include runoff, precipitation, weather, and water-quality data. Tables listing details of runoff, precipitation, lysimeter, weather, land-management, and other data are listed in [3] through about 2009 and are not repeated here. Due to specific project, financial, and personnel constraints during NAEW history, data for some watersheds such as runoff, precipitation and other data were not obtained for the entire 79-year period of monitoring. ARS operation of the NAEW ceased in late 2011, however, data collection continued from seven watersheds as part of a grant-funded project through Dec 2015 when all monitoring operations were discontinued. Through 2015, approximately 2125 station years of runoff data and 1126 station years of precipitation data were collected.

harvesting of high value crops, produces yields that are the same or greater than with conventional tillage (especially during droughts), increases soil-carbon storage (resulting in larger soil moisture for crops), and reduces energy needs. The environmental benefits of other types of

Experimental Watersheds at Coshocton, Ohio, USA: Experiences and Establishing New Experimental Watersheds

http://dx.doi.org/10.5772/intechopen.73596

13

Grazing: The NAEW developed environmental recommendations for pasture fertilizer application rates based on nitrogen [13, 14], sources of nitrogen fertility for pastures [15], and over-

Management-Intensive Grazing (MIG): The NAEW management-intensive grazing (MIG) project investigated the water-resource benefits of frequent rotation of livestock between small paddocks in a pasture for organic and non-organic production, and included impacts on surface and subsurface water quality, animal health, and changes in plant species [17]. Potential benefits of MIG to the producer include extended grazing season, less cost, and more leisure

Nutrient movement in stormflow vs. baseflow: Major transport of nutrients can occur in both

Preferential movement of water in soil: Fundamental knowledge from NAEW experiments on the fate of infiltrated water and chemicals in the subsurface through preferred pathways (e.g., earthworm burrows and cracks) has been used by scientists worldwide and in the development of a macropore component of a watershed model [19–21]. Additionally, guidance was

Evaluation of best management practices: A method was published to estimate the variability of chemical concentrations in runoff when there are few water samples and a history of runoff

Pesticide transport: Research on herbicide concentrations for weed control on watersheds showed that concentrations in runoff can reach levels of concern, particularly in the first few events after application, and that by reducing application rates by replacing herbicides with

conservation tillage have also been investigated [9–12].

baseflow and stormflow from mixed agricultural watersheds [18].

developed on manure application in tiled fields [22, 23].

short half-life types, concentrations can be reduced [25–27].

Figure 12. Original no-till experiments on steeply sloping experimental watershed.

using duration curves [24].

wintering practices on grazing lands [16].

time.

At the time of this writing, the NAEW data are being reviewed, corrected, and uniformly formatted from variety of original formats. The location for the data on the internet is yet to be determined. As part of the NAEW data-review process, a GIS of the NAEW has been developed documenting locations of runoff, precipitation, weather stations, etc. GIS will become part of the NAEW data base posted on the web site. The list of NAEW publications will also be posted.

Even though data collection has ceased, the database is valuable for further investigations of hydrology and water quality. Watershed modeling, in particular, can be studied at large (LMC —scaling, spatial parameterization of watershed models, and hydrology) and small scales (small watersheds—watershed modeling, hydrology, and water quality). The long precipitation and runoff records are valuable because they have experienced a wide array of weather conditions, even during a period of trending climate. Other precipitation, infiltration, soil moisture, ground water, and soil characterization data bases have not been analyzed and are available in hard copy form in the NAEW files. These data would have to be converted from hard copy to electronic form.


**3.1. Pathogen recognition**

Recognition of pathogen infection triggers an immunity system in the plant of two branches [13]. (i) In the first, common molecules are recognized in many classes of microorganisms, including those that are nonpathogenic and called immunity associated to pathogen-associated molecular patterns (PAMP)s or PAMP-triggered immunity (PTI). (ii) The second branch responds to factors of virulence and pathogenesis, so it is designated as effector-triggered immunity (ETI). Both mechanisms are described below (**Figure 2**).

PAMPs are considered as conserved elements by different classes of microorganisms and are essential for survival and pathogenicity [51]. Among the molecules identified as PAMPs for FOL, some components of their cell walls such as chitin, glucan, and glycoproteins are considered in this group due to their interaction with the host [52, 53].

The synthesis of chitin is regulated by the chsV gene and its expression depends on the Fmk1-MAPK signaling pathway. This was demonstrated with mutants of this gene, as they were unable to infect and colonize tomato plants or to grow invasively in tomato fruit tissue. In addition to this, hypersensitivity to defense compounds produced by the host was observed [54, 55].

A Molecular Vision of the Interaction of Tomato Plants and *Fusarium oxysporum* f. sp. *lycopersici* http://dx.doi.org/10.5772/intechopen.72127 85

**Figure 2.** Scheme of activation of the defense system by PTI and ETI in tomato plant.

**2.4. Lithic enzymes**

factor [44].

**3. Tomato plant**

observed [54, 55].

**3.1. Pathogen recognition**

The initiation of FOL infection requires degradation of the host cell wall through the action of a complex of enzymes with lytic activity such as xylanases, cellulases, pectinases, and polygalacturonases, which contribute to the penetration and colonization of the plant [42]. The genes xyl2 and xyl3 are responsible for the coding of xylanases, which degrade xylan. The xyl2 gene is expressed during the final stages of the disease, while xyl3 is present throughout the cycle [43]. The XlnR gene is known to be the main transcriptional activator of the xylanase genes. However, it was demonstrated that it is not determinant in the virulence of FOL, perhaps due to the presence of other xylanase genes whose expression is independent of this transcription

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

The PG1 and PG5 genes are responsible for the expression of extracellular endopolygalacturonases, the latter expressed mostly during the early stages of infection [45, 46]. On the other hand, the characterization of several enzymes with lytic activity, such as PG1, exo-polygalacturonases (PG2 and PG3), an endoxylanase (XYL1), and an endopectate lyase (PL1), has been reported. Coded by genes pg1, pgx4, pg5, xyl2, xyl3, prt1, and pl1, these are expressed during different stages of interaction with the host plant indicating a possible role in the pathogenesis [47, 48]. While the absence of the Fpr1 protein (F-box protein, required for pathogenicity) results in the lack of expression of some enzymes involved in cell wall degradation, this is

Recognition of pathogen infection triggers an immunity system in the plant of two branches [13]. (i) In the first, common molecules are recognized in many classes of microorganisms, including those that are nonpathogenic and called immunity associated to pathogen-associated molecular patterns (PAMP)s or PAMP-triggered immunity (PTI). (ii) The second branch responds to factors of virulence and pathogenesis, so it is designated as effector-triggered

PAMPs are considered as conserved elements by different classes of microorganisms and are essential for survival and pathogenicity [51]. Among the molecules identified as PAMPs for FOL, some components of their cell walls such as chitin, glucan, and glycoproteins are consid-

The synthesis of chitin is regulated by the chsV gene and its expression depends on the Fmk1-MAPK signaling pathway. This was demonstrated with mutants of this gene, as they were unable to infect and colonize tomato plants or to grow invasively in tomato fruit tissue. In addition to this, hypersensitivity to defense compounds produced by the host was

perceived as the inability of the pathogen to colonize the roots [49, 50].

immunity (ETI). Both mechanisms are described below (**Figure 2**).

ered in this group due to their interaction with the host [52, 53].

Glucans are also considered as elicitor molecules, although glucans may be present in the cell wall of both plants and fungi, *β*-1,6-glucan is specific to the cell wall of fungi, resulting in a potential PAMP [56]. Glycoproteins present in the cell wall of FOL, whose function is the adhesion of hyphae to plant tissue, are encoded by the Fem1 gene and are considered within this group [57]. Each of these elements can be recognized by the plant defense system since it has pattern recognition receptors (PRR) [58]. Plant PRRs are located on the surface of the plasma membrane and can be two types. The receptor-like kinases (RLK) contain a ligand-binding ectodomain, a single-pass transmembrane domain, and an intracellular kinase domain. Or they may be receptor-like proteins (RLPs) typically consisting of a repetitive domain rich in extracellular leucine, a transmembrane domain, and a short cytoplasmic tail [59–61].

To date, chitin has been the most extensively studied PAMPs; the presence of a receptor for chitin in rice cells has been detailed [62], while in *Arabidopsis thaliana*, an RLK-type lysin motif receptor-like protein (LysM RLK1) with an extracellular domain containing three predicted LysM motifs has been detailed. These studies have shown that the binding between the receptor and chitin is specific and direct. However, this interaction is not a simple ligandbinding reaction but could be accompanied by a conformational change of the receptor protein. This allows it to participate in signaling leading to gene induction and defense responses against pathogenic fungi [63, 64]. On the other hand, little is known about the mechanism of recognition of glucans as PAMPs in tomato plants. In soybeans, a glucanelicitor–binding protein (GEBP) harbored a glucanase domain and a high-affinity glucan binding motif, which makes this protein a powerful tool to release and detect elicitor fragments of the pathogen [65].