**3. Microbiological control of Fusarium soilborne pathogens**

Current findings have shown that plant diseases resulting from soilborne plant pathogens' contamination are complicated to manage. However, various investigations have recognized the renowned biological control of soilborne pathogens using antagonistic microorganisms [16]. Previous studies have demonstrated that besides the most popular *Penicillium* spp., *Pseudomonas* spp., *Streptomyces* spp. (*Streptomyces griseoviridis*), and *Trichoderma* spp. (*T. harzianum*, *T. asperellum*, *T. koningii*), which represent the most broadly investigated groups of biological control agents, the Fusarium *species* can also be used to control plant diseases [2]. Among *Fusarium* species that cause soilborne pathogens, there is *F. emeriti*, *F. avenaceum*, *F. solani*, *F. sulphureum*, *F. tabacinum*, and *Fusarium oxysporum (F. oxysporum)*, which is also commonly known to cause vascular wilt in economically important crops. Among *F. oxysporum* include pathogenic and nonpathogenic strains. Research findings have pointed out that *F. oxysporum* as a biological agent can only control wilt originated from diverse pathogenic strains from similar species. However, more research is required to investigate if they cannot control wilt from other pathogenic species. Moreover, the mechanism involved in inducing the protective capacity of *F. oxysporum* is still not well understood [17].

Ortoneda et al. [18] investigated *Fusarium oxysporum* virulence mechanisms in plant and mammalian species. It was found that a single strain of *Fusarium* infection can induce vascular wilt disease in the plant. While the inoculation of microconidia of the tomato pathogenic isolates in the lateral tail vein of immunocompromised, mice can cause extensive complications such as the dissemination of infection in all organs and the death of the mice. More findings from the same study established that removing the mutant genes regulating a mitogen-induced protein kinase, a class V chitin synthase, and a pH response transcription factor affect diverse virulence factors important in both the tomato plants and mouse pathogenicity. Supportive studies have confirmed that *F. oxysporum* can suppress Fusarium wilts, and therefore, the utilization of this Fusarium strain to reduce the virulence capacity of other diseases due to Fusarium is recommended (**Figure 1**) [19, 20].

Relatively, little is understood about the interactions of plant pathogens, soil microbiome, and myxobacteria strains to reduce soilborne phytopathogens. Ye et al. [16] indicated that a predatory myxobacterium *Corallococcus* sp. strain EGB can be used to minimize cucumber Fusarium wilt through its capacity to colonize plant roots, thereby influencing the ability of the soil microbial community. The research findings done in two-year field experiment has shown that the inoculation of the solid-state fermented *Corallococcus* sp. strain EGB controlled the cucumber Fusarium wilt by 79.6% in the greenhouses, 66.0% in the field in 2016, and 53.9% in the field in 2016, and the analysis of the capacity of strain EGB showed that it could improve the soil microbial community while reducing effectively the soilborne (*Fusarium oxysporum f.sp. cucumerinum*). Therefore, it was concluded that *Corallococcus* sp. has significant potential as a new biological control agent of soilborne pathogens, in particular Fusarium wilt. Due to the inefficient current techniques used to reduce vascular wilt pathogens in various important crops, more research is needed to explore and develop novel biological control agents and the currently available strains such as nonpathogenic *Fusarium*, *Pseudomonas*, *Streptomyces*, *Trichoderma*, *Gliocladium*, *and Coniothyrium* [21].

More research findings have confirmed that diverse bacterial and fungal strains can control Fusarium wilt in soil. A comparative analysis of meta-barcoding of taxonomic diversity of bacterial and fungal organisms from non-suppressive and suppressive soils concerning the control of Fusarium wilt has shown that bacterial and fungal strains recognized for their antagonistic activity against *F. oxysporum* was detected in suppressive and non-suppressive soils [22].

Fusarium wilt of banana (FWB), in particular, *Fusarium oxysporum* f.sp. cubense (Foc) race one has caused a considerable loss of banana plantations due to its distribution in tropical areas. However, researches show that FWB has been reduced up to 79% by employing *Pseudomonas* spp. and approximately up to 70% by various endophytes and *Trichoderma* spp. The use of another biological agent to control FWB is recommended to support the currently available techniques [22].

Actinomycetes obtained from soil have been found to inhibit Fusarium *Solani f.sp. pisi* that causes black root rot in Chickpea. A hundred actinomycetes were tested for their antifungal activities against *F. solani in vitro* and *in vivo*. The identifications result of actinomycetes used in the experiment showed that the isolates S3 of actinomycetes were highly similar to *Streptomyces* antibiotics, while the isolates s40 have similarities with *Streptomyces peruviensis*. From these results, it can be concluded that the actinomycetes and bacteria can minimize the effect of fungi. More studies should be conducted to produce these biocontrol en masse to confirm their biocontrol capacity and potential for commercialization as biocontrol agents [23].

## **4. Chemical control methods of Fusarium soilborne pathogens**

Soilborne diseases can be reduced by spraying and fumigating with chemicals such as fungicides or biocontrol agents. Song et al. [24] investigated the capacity of seven fungicides, carboxin, azoxystrobin, hymexazol, tolclofos-methyl, thiram, carbendazim, and prochloraz, against *Fusarium oxysporum* Klotz on the Tomato (*Lycopersicon esculentum* Mill) plant grown in a hydroponic system. The inhibitory activities of these fungicides against the *F. oxysporum* findings showed that the median concentration (EC50) was 154.03, 144.58, 69.961, 53.606, 26.292, 0.235, and 0.019 μg.ml–1, respectively. Among all the fungicides used, prochloraz and carbendazim were found very efficient in controlling the mycelial growth of *F. oxysporum*. These results confirmed that wild tomato disease due to the infection of Fusarium pathogens could be inhibited by minimum toxicity of fungicides, using measured concentrations.

A similar study by Chauhan et al. [25] established the use of chemical fungicides, carboxin, carbendazim, quintozene, and thiram for seed management, pre- and post-sowing soil drench, and seed treatment of cotton can potentially reduce the occurrence of soil pathogens: *Fusarium oxysporum sp. Vasinfectum* (Atk.) Snyder and Hansen, *Macrophomina phaseolina* (Tassi) Goid = *Rhizoctonia bataticola*

#### *Fusarium Soilborne Pathogen DOI: http://dx.doi.org/10.5772/intechopen.100597*

(TAUB.) Butler, *Rhizoctonia solani* (Kuhn) and *Fusarium solani* (Mart.) Sacce. However, the use of the chemicals has several disadvantages, such as the inability to perform under various environmental and biotic conditions. Commonly used fungicides are usually inexpensive, but their efficacy is disputed due to the complications associated with diverse pest management strategies.

Nitrate nitrogen added to the soil at a higher pH has been used to control Fusarium wilt effectively [25]. A similar study has also reported that the use of nitrate-nitrogen significantly reduced the occurrence of Fusarium wilt on chrysanthemums, King asters, and carnations [26, 27]. Potassium quantity in soil has also been related to the occurrence of soilborne diseases and crop production. However, research has demonstrated that Fusarium soilborne pathogens incidence in tomatoes can be minimized by increasing potassium quantity in soil [28]. Similar studies have confirmed that high potassium levels can reduce the severity of Fusarium wilt in cotton [29]. The quantity of phosphate in soil has been investigating for its association with Fusarium diseases in crops. The findings revealed that higher phosphate quantity was associated with the occurrence of Fusarium wilt in muskmelon and cotton [30].

Numerous studies have established that the use of chemical disinfection to restore and prevent the occurrence of Fusarium wilt is not sustainable due to the environmental concerns because of the high toxicity and deteriorating effects of these chemical fungicides as well as the development of fungicides resistance; therefore, alternative control methods are recommended. Among the highly preferred methods include deep plowing, rotation, heating, grafting techniques, flooding, solarization, and various pesticides. Biofumigants and crop rotations are also among the environmental friendly methods that can be used to control soilborne pathogens especially Fusarium wilt. The methods to apply should be selected depending on the location and climate. Some methods such as soil solarization are ineffective where solar radiation is inefficient, while soil flooding requires a more extended period, approximately between 3 and 4 months, and is not preferred when the quantity of soil pathogens is high [6, 31–33].
