Keywords

1 Introduction

Fusarium is a very interesting genus compared with other genera of fungi. Fusarium in the pathogenic state can cause very hazardous diseases in plants and human. Fusarium and other fungi produced very dangerous secondary metabolites such as mycotoxins (Attitalla et al. 2010a, b; Nor Azliza et al. 2014). While the genus can be useful in avirulent state, in this state it is known as non-pathogenic Fusarium. Many species of non-pathogenic Fusarium inhabit the tissues of plants as endophytic fungus or as saprophytes in soil. Non-pathogenic Fusarium can live for a long time in soil, in rhizosphere and in planta (Singh et al. 2016, 2017).

Non-pathogenic Fusarium are endophytes in many crops in agricultural ecosystems (Burgess 1981; Leslie et al. 1990; Kuldau and Yates 2000). Non-pathogenic Fusarium can invade internal plant tissues without causing any symptoms (Burgess 1981). Some non-pathogenic Fusarium isolated from healthy rakkyo roots (Allium chinense) after 97 days including F. fujikuroi, F. solani and F. oxysporum (Honda and Kawakubo 1999). Some non-pathogenic or endophytic Fusarium were isolated from five species of the medicinal plants in the Western Ghats of India (Raviraja 2005). The fungal biomass of non-pathogenic Fusarium strains could differ from other pathogenic F. oxysporum strains present in the root cortex (Validov et al. 2011). Three species of non-pathogenic Fusarium, viz. F. oxysporum, F. solani and F. fujikuroi, were reported to be dormant in the rhizosphere of tomato (Imazaki and Kadota 2015). Non-pathogenic Fusarium are highly diverse in soil, in rhizosphere and in the roots of tomato (Demers et al. 2015). The non-pathogenic Fusarium, viz. F. fujikuroi, F. solani, F. proliferatum and F. polyphialidicum, were among the fungal flora isolated from the roots of banana (Cao et al. 2002; Al-Ani 2017b). Many strains of non-pathogenic F. oxysporum were also isolated from healthy banana (Nel et al. 2006b; Al-Ani 2017b).

Some antimicrobial compounds produced by plants affect the growth of pathogenic Fusarium, exclusively (Mishra et al. 2015). Landa et al. (2002) reported phytoanticipins including biochanin A and tomatine, which inhibit the growth of pathogenic Fusarium, while enhancing the growth of non-pathogenic Fusarium. Also, coumarin could inhibit the growth of both non-pathogenic and pathogenic Fusarium. Different species of non-pathogenic Fusarium could be efficiently used for the management of various phytopathogens by reducing infection of plant-parasitic nematodes, bacteria and fungi (Bisen et al. 2015; Keswani et al. 2016). Indeed, non-pathogenic Fusarium can utilize as biocontrol agent such as other biocontrol agents. Many biocontrol agents with natural products were used in controlling the plant pathogens and pests (Al-Ani 2006; Al-Ani and Salleh 2013b; Mohammed et al. 2011, 2012, 2013, 2014; Al-Ani and Al-Ani 2011; Al-Ani et al. 2012; Al-Ani et al. 2013a, b; AL-Ani 2017a, b; Al-Ani and Albaayit, 2018a, b; Al-Ani et al. 2018; AL-Ani 2018a, b; Al-Ani 2019a, b, c, d, e; Al-Ani et al. 2019). Other methods are including several methods such natural products (Mohammed et al. 2012; Al-Ani et al. 2012). Non-pathogenic Fusarium have been effectively employed for management of Fusarium wilt of many important agricultural crops, including banana (Nel et al. 2006a; Al-Ani 2010, 2017b; Al-Ani et al. 2013a), tomato (Lemanceau and Alabouvette 1991; Larkin and Fravel 1998), chickpea (Hervás et al. 1995), cucumber (Mandeel and Baker 1991; Wang et al. 2013), watermelon (Larkin et al. 1996; Freeman et al. 2002), basil (Fravel and Larkin 2002), celery (Schneider 1984), strawberry (Tezuka and Makino 1991), muskmelon (Freeman et al. 2002), cyclamen (Minuto et al. 1995) and flax (Lemanceau and Alabouvette 1991). Also, non-pathogenic Fusarium is compatible with other biocontrol agents and be very efficiently involved in integrated pest management. Belgrove et al. (2011) used non-pathogenic F. oxysporum with Pseudomonas fluorescens WCS 417 against pathogenic F. oxysporum f. sp. cubense race 4 demonstrating effective suppression and protection of banana cultivar from Panama disease (Fusarium wilt). Also, application of consortia of non-pathogenic Fusarium and Trichoderma proved to be highly effective in reducing the vanilla shoot rot disease (Taufiq et al. 2017).

The efficacy of non-pathogenic Fusarium in the production and secretion of diverse and bioactive secondary metabolites was contributed to the management of phytopathogens (Jayaprakashvel and Mathivanan 2011), while other mechanisms include mycoparasitism, competition and induced resistance in host (Fravel and Larkin 2002; Kaur et al. 2010; Shishido et al. 2005).

2 Secondary Metabolites

Secondary metabolites produced by biocontrol agents are highly effective in controlling phytopathogens. Non-pathogenic Fusarium produces an array of chemically diverse, bioactive secondary metabolites. Non-pathogenic Fusarium secretes low molecular weight volatile organic compounds (VOCs) (Weikl et al. 2016). Non-pathogenic Fusarium produces several secondary metabolites which were absent in its pathogenic counterpart. Nawar (2016) reported that GC-MS analysis of the cultural filtrate of non-pathogenic Fusarium had as many as 30 secondary compounds compared with 22 for the pathogenic isolate.

Two antifungal compounds of F. chlamydosporum were able to inhibit the growth of uredospore of Puccinia arachidis (Mathivanan and Murugesan 1998). α-Pyrones, viz. fusapyrone (FP) and deoxyfusapyrone (DFP), were reported to be produced by F. semitectum (Evidente et al. 1999). DFP and FP inhibited the growth of many filamentous fungi such as Alternaria alternata, Penicillium verrucosum, P. brevicompactum, Ascochyta rabiei, Aspergillus flavus, Cladosporium cucumerinum, Phoma tracheiphila, Botrytis cinerea, Candida albicans, C. glabrata and Cryptococcus neoformans (Altomare et al. 2000; Bartelt and Wicklow 1999; Garret and Robinson 1969; Mathivanan and Murugesan 1999). Non-pathogenic F. oxysporum MSA35 strain produces many VOCs which are highly effective against pathogenic F. oxysporum f. sp. lactucae Fuslat10 (Minerdi et al. 2009). Volatile compounds of MSA35 strain such as α-humulene efficiently reduced the mycelial growth and inhibited the virulence gene of pathogenic Fuslat10 strain (Minerdi et al. 2009). α-Humulene extracted from non-pathogenic MSA35 was effective on pathogenic Fuslat10 strain at 25–100 mM but at 5–20 mM was completely ineffective (Minerdi et al. 2009). The strain CanR-46 of F. oxysporum was producing four VOCs including limonene, octanoic acid, 3,4-2H-dihydropyran and 5-hexenoic acid effective against V. dahliae (Zhang et al. 2015).

For control of the plant parasitic nematodes, non-pathogenic F. solani produced secondary metabolites affecting the juveniles of Meloidogyne javanica (Siddiqui and Shaukat 2003). Two species of endophytic Fusarium such as F. oxysporum and F. solani secrete some secondary metabolites as nematicidal agents against second-stage juveniles of Meloidogyne javanica (Qureshi et al. 2012). Non-pathogenic F. oxysporum produced VOCs against second-stage juveniles of Meloidogyne exigua causing high mortality and immobility after 72 h (Costa 2014). For control of bacterial plant pathogens, endophytic F. oxysporum NRRL26379 in A. thaliana (A) reduced the disease severity of Pseudomonas syringae (Col-0), (B) improved the plant growth and (C) increased salt tolerance by producing volatile compounds (Li and Kang 2018).

For control of the plant parasitic weeds, endophytic Fusarium produces some toxins that can be highly beneficial for field applications. Zonno and Vurro (2002) isolated endophytic Fusarium secreting several toxins such as nivalenol, T-2, neosolaniol, HT-2 and diacetoxyscirpenol that were able to inhibit 100% plant parasitic weed Orobanche ramosa. Two endophytic Fusarium could produce some secondary metabolites as mycoherbicidal agents that are highly effective for growth inhibition of Orobanche aegyptiaca (Egyptian broomrape) of tomato (Cohen et al. 2002a). These species including F. oxysporum produced fusaric acid and fumonisin-like ceramide synthase inhibitors (Cohen et al. 2002a). Beauvericin (as toxin) could significantly improve the secondary metabolite content and plant growth in plant Dioscorea zingiberensis (a traditional Chinese medicinal herb), which was produced by endophytic F. redolens Dzf2 (Campos et al. 2011; Yin et al. 2011). Fusarium sp. KF611679 strain of Brazilian tree Caesalpinia echinata Lam. was secreting a trypanocidal metabolite as beauvericin (Campos et al. 2015). The LC-MS analysis of secondary metabolites for four endophytic Fusarium species such as F. oxysporum, F. solani, F. subglutinans and F. verticillioides isolated from symptomless weeds produced some main compounds comprising beauverin, cyclosporines, enniatins, equisetin, fusaric acid, integracide A and trichosetin (Ilic et al. 2017). Among these compounds equisetin, fusaric acid, beauvericin and enniatins acted as mycotoxins, while trichosetin was an efficient antibacterial compound.

Endophytic Fusarium isolated from the inner bark of Taxus baccata L. was found to be producing some antimicrobial compounds (Tayung and Jha 2010). Endophytic fungi Fusarium were secreting antibacterial compounds active against several pathogenic bacteria including Staphylococcus epidermis, S. aureus, Bacillus subtilis, Klebsiella pneumoniae, Escherichia coli and Shigella flexneri, as well as some antifungal compounds active against pathogenic fungi Candida tropicalis and C. albicans (Tayung and Jha 2010). In addition, endophytic F. oxysporum of plant rhizome Acorus calamus was found to be producing secondary metabolites with antimicrobial activity against many pathogenic microorganisms (Barik et al. 2010). Endophytic F. solani showed high inhibition of six bacteria such as Staphylococcus aureus, S. epidermidis, Bacillus subtilis, Klebsiella pneumoniae, Shigella flexneri and E. coli and two fungi, viz. Candida tropicalis and C. albicans, by secreting antimicrobial secondary metabolites (Tayung et al. 2011a, b). These antimicrobial compounds were analysed using GC-MS for the crud metabolites of F. solani including (1) dodecene, (2) hexylcyclohexane, (3) 1-tetradecene, (4) tetradecane, (5) octylcyclohexane, (6) 10-nonadecanone, (7) 8-pentadecanone and (8) 8-octadecanone (Tayung et al. 2011a). For antibacterial activity, endophytic strain BH-3 of F. oxysporum from the bulbs of Lilium lancifolium produced secondary metabolites as antibacterial against Leuconostoc mesenteroides (Liu et al. 2012).

Several secondary compounds such as ergosterol-5,8-peroxide, triterpene acetate and cerebroside were isolated from endophytic Fusarium (Effendi 2004). Strain K178 of Fusarium maire was able to produce the anticancer compound paclitaxel (Taxol) (Xu et al. 2006). Endophyte F. solani was also reported to produce paclitaxel (Chakravarthi et al. 2008; Deng et al. 2009). Endophyte F. arthrosporioides also secreted a Taxol compound (Li et al. 2008). Two secondary metabolites, viz. camptothecin and 10-hydroxycamptothecin, were produced by two endophytic strains MTCC 9667 and MTCC 9668 of F. solani isolated from plant Apodytes dimidiata (Icacinaceae), and these compounds are used as anticancer drugs, topotecan and irinotecan (Shweta et al. 2010). An anticancer compound rohitukine was secreted by endophytic F. proliferatum (MTCC9690) from plant Dysoxylum binectariferum (Kumara et al. 2012). A Taxol compound with anticancer activity was isolated from F. solani (Tayung et al. 2011a). Endophytic F. oxysporum from mangrove leaves Rhizophora annamalayana was also secreting a Taxol compound (Elavarasi et al. 2012). Endophytic F. oxysporum isolated from the root bark of G. biloba was reported to produce ginkgolide B (Cui et al. 2012). A podophyllotoxin as anticancer was produced by some endophytic F. oxysporum that was isolated from medicinal plant Juniperus recurva (Kour et al. 2008). Endophytic F. solani strain P1 was producing 29.0 μg/g of podophyllotoxin, this strain isolated from roots of Podophyllum hexandrum in Himalayan region (Nadeem et al. 2012). A Taxol compound was secreted by endophytic F. redolens that was isolated from plant Taxus baccata L. subsp. wallichiana (Garyali and Reddy 2013).

In additional, F. oxysporum NFX06 strain from plant Nothapodytes foetida (Musavi et al. 2015), and endophytic F. solani MTCC 9668 (Venugopalan et al. 2016), could produce anticancer compound camptothecin. However, the endophytic strain ZZF60 of Fusarium from mangroves forest secreted several secondary compounds including (1) 5-hydroxy-7-methoxy-40-O-(3-methylbut-2-enyl) isoflavone, (2) vittarin-B, (3) 3,6,7-trihydroxy-1-methoxyxanthone, (4) eriodictyol, (5) cyclo(Phe-Tyr) and (6) 1,3,6-trihydroxy-8-methylxanthone (Huang et al. 2012). Endophytic F. oxysporum could produce anticancer drug vincristine by converting vinblastine to vincristine (Kumar and Ahmad 2013; Kumar et al. 2013). Endophytic Fusarium isolated from the fresh bulbs of Fritillaria unibracteata var. wabensis produced some medicinal compounds such as peiminine and peimisine (Pan et al. 2014). F. redolens 6WBY3 isolated from bulbs of Fritillaria unibracteata var. wabuensis was secreting imperialine-3β-D-glucoside and peimisine (Pan et al. 2015). Five isolates of endophytic Fusarium such as F. oxysporum (one isolate), F. incarnatum (two isolates) and F. solani (two isolates) produced cinchona alkaloids, such as quinine, quinidine, cinchonine and cinchonidine (Hidayat et al. 2016). Weikl et al. (2016) demonstrated the ability of non-pathogenic Fusarium to produce the complex VOCs such as sesquiterpenes.

3 Other Mechanisms

Honda and Kawakubo (1998) used simultaneously two isolates of non-pathogenic Fusarium from healthy root of rakkyo (Allium chinense), viz. F. oxysporum and F. moniliforme against F. oxysporum f. sp. allii causing basal rot of rakkyo. The mode of action for non-pathogenic Fusarium could include several mechanisms including competition for nutrients and infection sites, induced resistance, etc., but the efficacy of these mechanisms depends on the kind of strain and isolates (Fravel et al. 2003).

3.1 Mycoparasitism

Benhamou et al. (2002) reported the ability of non-pathogenic F. oxysporum Fo47 strain to attack other fungal pathogens. The Fo47 strain could inhibit the mycelial growth of Pythium ultimum causing damping-off of cucumber and reported the ability of Fo47 to grow inside the cells of P. ultimum (Benhamou et al. 2002). Non-pathogenic F. oxysporum S6 could attack the sclerotia of Sclerotinia sclerotiorum, considered as a mycoparasite (Rodrıguez et al. 2006). Also, Tsapikounis (2015) reported several isolates of Fusarium able to mycoparasitism on the sclerotia of Sclerotinia sclerotiorum.

3.2 Antibiosis

Non-pathogenic Fusarium produces hydrolytic enzymes and secondary metabolites inhibiting the growth of plant pathogens without direct physical contact. Fo47 strain of non-pathogenic Fusarium secretes some antifungal against P. ultimum (Benhamou et al. 2002). Two strains of non-pathogenic Fusarium such as F. solani CS-1 and F. oxysporum CS-20 were inducing the systemic resistance in some vegetables such as watermelon (Citrullus lanatus) and tomato (Lycopersicon esculentum) against Fusarium wilt (Larkin and Fravel 1999). Endophytic F. equiseti produced two trichothecene compounds, viz. 4,15-diacetoxy-12,13-epoxy-trichothec-9-en-3-ol (diacetoxyscirpenol) and 4,15-diacetoxy-12,13-epoxy-3,7-dihydroxytrichothec-9-en-8-one (4,15-diacetylnivalenol), very effective against Meloidogyne incognita causing the egg-hatching inhibition and immobilization of juveniles at second stage (Nitao et al. 2001).

Additionally, cyclosporine produced by F. oxysporum strain S6 could inhibit the formation of sclerotia of Sclerotinia sclerotiorum (Rodrıguez et al. 2006). Non-pathogenic F. oxysporum was inducing in pepper some bioactive compounds against pathogenic V. dahliae including caffeic acid, ferulic acid and chlorogenic acid (Veloso et al. 2016). High antifungal activity against spore germination of some plant fungal pathogens was detected in the culture filtrate of non-pathogenic F. oxysporum strain F221-B (Thongkamngam and Jaenaksorn 2016). This antifungal of F221-B strain could cause damage to the spores (Thongkamngam and Jaenaksorn 2016). The cell-free culture filtrates of endophytic F. proliferatum I92 showed antifungal activity against fusarium crown and root rot in tomato (Nefzi et al. 2018).

3.3 Competition

Non-pathogenic Fusarium compete with plant pathogens for space and nutrients (Nagao et al. 1990; Couteaudier and Alabouvette 1990; Alabouvette 1990; Larkin and Fravel 1999; Benítez et al. 2004). This competition for nutrients is important for non-pathogenic Fusarium for growth and sporulation. Non-pathogenic Fusarium strain Fo47 could compete for carbon with pathogenic F. oxysporum (Duijff et al. 1998). Larkin and Fravel (1999) demonstrated the ability of non-pathogenic F. oxysporum strain Fo47 for competing for glucose with the pathogenic F. oxysporum. Competition was observed between pathogenic F. oxysporum f. sp. lycopersici and non-pathogenic F. oxysporum for root exudates on the surface of the tomato roots (Olivain and Alabouvette 1999). Non-pathogenic F. oxysporum Fo47 strain was competing for nutrients with pathogenic F. oxysporum f. sp. lycopersici Fo18 strain (Olivain et al. 2006). Two strains ML-5-2 and HK-5b-4-1 of non-pathogenic F. oxysporum were competing with F. oxysporum f. sp. vanillae for nutrients (Xia-Hong 2007).

Gizi et al. (2011) applied the F2 strain of non-pathogenic F. oxysporum against pathogenic Verticillium dahlia that F2 strain reduced 68% of Verticillium wilt disease incidence in eggplant by competing for nutrient and space at the surface and inside the roots. Non-pathogenic Fusarium competed for nutrients with F. oxysporum f. sp. niveum that reduced Fusarium wilt of V. villosa (Himmelstein 2013). Fo47 strain was competing for nutrients with pathogenic V. dahliae on root surface of pepper (Veloso et al. 2016). Some isolates of non-pathogenic Fusarium could produce a siderophore to compete for iron with pathogenic F. oxysporum f. sp. cubense tropical race 4 (FocTR4) LJ27 strain from banana of Palau Penang in Malaysia that lead to high reduction of Fusarium wilt disease of banana (Al-Ani 2017b).

3.4 Induced Plant Resistance

The induced resistance in plants is a mode of action that affects the pathogens indirectly (Al-Ani 2018a). Non-pathogenic Fusarium sp. is able to induce the plant resistance (Benhamou and Garand 2001). The plant resistance is restricted to the proliferation of non-pathogenic Fusarium in the inner roots (Validov et al. 2011).

The Fo47 strain of non-pathogenic F. oxysporum showed high efficacy against F. oxysporum f. sp. lycopersici causing Fusarium wilt of tomato through the split root methods (Fuchs et al. 1997). The split root system includes four methods: (A) benomyl system, (B) split root system, (C) cutting system and (D) layering system (Fuchs et al. 1997). Non-pathogenic F. oxysporum Fo47 strain could induce systemic resistance in tomato plant by accumulating both PR-1 proteins and chitinases (Duijff et al. 1998). The split root is a very interesting method for detecting the ability of non-pathogenic Fusarium isolates to induce plant resistance. Volatile compounds of non-pathogenic Fusarium could induce the plant resistance against Pseudomonas syringae in Arabidopsis thaliana (Bitas and Kang 2012). The process of induced resistance through non-pathogenic F. oxysporum Fo47 strain in cucumber against P. ultimum was demonstrated by Benhamou et al. (2002). The systemic resistance was induced through upregulating some defence-related gene, viz. POX, PIR7A, lectin, PR-3, PAE, PAL, catalase and PR-1, against Radopholus similis through treating banana (Musa spp.) with non-pathogenic F. oxysporum (Paparu et al. 2007).

3.5 Induced Plant Defences

Non-pathogenic Fusarium has the ability to induce plant defence (Paparu et al. 2007). The modulation of phytohormone regulators such as jasmonic acid, ethylene, abscisic acid, salicylic acid and auxin by non-pathogenic F. oxysporum strains leads to induction plant defence network (Di et al. 2016). Olivain et al. (2003) observed non-pathogenic F. oxysporum having the ability to induce the plant defence in flax plant by affecting the host physiology against pathogenic F. oxysporum f. sp. lini Foln3 strain.

Non-pathogenic Fusarium, viz. F. oxysporum, F. moniliforme, F. merismoides and F. solani, induced the plant defences by activating and increasing the polyphenol oxidase and peroxidase content in tomato when (A) directly treated with the spore suspension and (B) extraction of cell wall elicitors (Patil et al. 2011). Many strains of non-pathogenic Fusarium could induce the plant defences enzymes such as phenylalanine ammonia lyase (PAL), β-1,3-glucanase, polyphenol oxidase (PPO), chitinase and peroxidase (POD) that inhibited the pathogenic growth in watermelon (Raghunandan 2013). Fo47 strain of non-pathogenic F. oxysporum could induce the defence genes such as a class II chitinase (CACHI2), basic PR-1 protein (CABPR1) and sesquiterpene cyclase (CASC1) in pepper against Phytophthora capsici and Verticillium dahliae (Veloso and Díaz 2012). Enhancement in the activities for three enzymes, viz. PPO, POD and PAL, in Chinese herbal Dioscorea zingiberensis was observed when treated with three oligosaccharides from endophytic Fusarium oxysporum Dzf17 strain (Li et al. 2012; Li et al. 2014). The gene expression of PR3, LOX1, PAL1, CsCam12, NPR1 and CsCam7 could be induced through inoculation of non-pathogenic F. oxysporum CS-20 in cucumber roots (Pu et al. 2014). Fo47 strain has the ability to induce plant defences through jasmonyl isoleucine and salicylic acid in pepper against the pathogen V. dahliae (Veloso et al. 2016). Three compounds comprising 4-hydroxybenzoic acid, gibepyrone D and indole-3-acetic acid (IAA) produced by non-pathogenic F. oxysporum 162 could induce plant defence against plant pathogenic nematodes (Bogner et al. 2017).

3.6 Induced Changes in Phytochemistry

Non-pathogenic Fusarium induce changes in phytochemistry (Huang et al. 2008). A non-pathogenic Fusarium strain Rs-F-in-11 was observed to be eliciting the metabolic pathway against strain Py71–1 of Pythium ultimum in Lepidium sativum (Ishimoto et al. 2004). Ishimoto et al. (2004) found that strain Rs-F-in-11 induced myrosinase enzyme in roots of L. sativum and this enzyme catalysed the hydrolyzation of glucosinolates to isothiocyanate, leading to the accumulation of isothiocyanates in the roots.

Non-pathogenic Fusarium as endophyte can alter the phenolic profile including ferulic acid, vanillic acid and caffeic acid in the leaves and roots of tomato against pathogenic F. oxysporum f. sp. lycopersici (Panina et al. 2007). The strain 162 (FO162) of non-pathogenic Fusarium could colonize tomato and induce the roots to produce the repellent substance against nematode M. incognita juveniles (Dababat and Sikora 2007). Endophytic F. oxysporum strain Fo162 could induce changes in the proliferation of banana root affecting the growth of nematode Radopholus similis (Kurtz 2010). Three polysaccharides, viz. exopolysaccharide, sodium hydroxide-extracted mycelial polysaccharide and water-extracted mycelial polysaccharide of endophytic F. oxysporum Dzf17, affected the biosynthesis of secondary metabolites and growth for Dioscorea zingiberensis (Li et al. 2011a, b). Some non-pathogenic Fusarium isolates were inducing the free phenol content and total protein content in tomato (Patil et al. 2011) and watermelon (Raghunandan 2013).

3.7 Non-pathogenic Fusarium as Biofertilizers

Non-pathogenic Fusarium enhance the plant growth by producing the gibberellic acid (GA) (Leslie 1996), IAA (Bogner et al. 2017) and siderophores (Al-Ani 2017b) and enhance the nutrient utilization efficiency (Zhang et al. 2012). Louter and Edgington (1990) reported the ability of non-pathogenic Fusarium such as F. oxysporum and F. solani in reducing the tomato root rot and increased the yield. However, endophytic Fusarium such as F. arthrosporioides and F. oxysporum were pathogenic for plant parasitic Orobanche aegyptiaca though affecting the size and number of shoots for O. aegyptiaca by producing IAA (Cohen et al. 2002b). The high production of IAA was for co-transforming two genes both of iaaH and iaaM in Fusarium that was probably increased for suppressing the appressoria formed on infected Orobanche aegyptiaca through attack on tomato (Cohen et al. 2002b). Some strains of non-pathogenic Fusarium can reduce the plant diseases and simultaneously enhance the plant growth. The KGL0401 strain of F. proliferatum was reported to produce several new gibberellins (GAs) (Rim et al. 2005). The conidial suspension 108–109 (spores/ml) of F. oxysporum B6 significantly enhanced various plant growth parameters such as leaf length and leaf area, plant height and root fresh weight (Mennan et al. 2005).

In addition, endophytic Fusarium improved plant growth by secreting gibberellin (GA), indole acetic acid (IAA) and auxin (Dai et al. 2008). Thangavelu and Jayanthi (2009) reported a very effective strain of non-pathogenic F. oxysporum Ro-3 for reducing Fusarium wilt severity of banana. F. oxysporum Ro-3 also increased plant height, petiole length, leaf area, girth and the number of leaves (Thangavelu and Jayanthi 2009). Bitas and Kang (2012) reported an isolate of F. oxysporum producing VOCs that enhanced the plant growth by promoting root and shoot growth in A. thaliana. Also, non-pathogenic Fusarium increased the plant growth of watermelon by producing the IAA and GA with the solubilization for phosphate (Raghunandan 2013). F. oxysporum could enhance the plant growth of A. thaliana and tobacco by producing many volatile compounds (Bitas et al. 2015). Also, LeBlanc (2015) isolated many non-pathogenic Fusarium producing secondary metabolites such as bikaverin (BIK), IAA and GA. F. solani I149 isolate also improved plant growth in axenic cherry plants (Ilic et al. 2017), while endophytic F. proliferatum I92 enhanced plant growth in tomato (Nefzi et al. 2018).

3.8 Secreting the Enzymes

Non-pathogenic Fusarium produce many hydrolytic enzymes. β-D-glucuronidase (GUS) was detected by using a new method in the tomato roots that were treated with 70 T01 strain of non-pathogenic F. oxysporum (Bao and Lazarovits 2002). Myrosinase was produced by non-pathogenic Fusarium strain Ls-F-in-4-1 that inhibited the mycelial growth of P. ultimum strain Py71-1 (Ishimoto et al. 2004). Endophytic F. proliferatum I92 could produce several hydrolytic enzymes, viz. chitinase, lipase, amylase and proteases, that may affect Fusarium crown and root rot in tomato (Nefzi et al. 2018).

4 Conclusion

Non-pathogenic Fusarium are soil-borne fungi, as well as an endophyte in the host system. This genus produces a variety of chemically diverse secondary metabolites. Some of the secondary metabolites have been identified but many are yet to be identified. Non-pathogenic Fusarium has other mechanisms that are very useful for agricultural production. Non-pathogenic Fusarium plays a huge role in agriculture through production of bioactive secondary metabolites having diverse functions. Other modes of actions include (1) induction of host defence response, induction of resistance genes and secretion of some plant activators; (2) secretion of various antibiotics against phytopathogens; (3) restricting the nutrient supply to competing microorganisms; and (4) production of hydrolytic enzymes that may be utilized against plant pathogens.

Non-pathogenic Fusarium can be separated from pathogenic Fusarium by pathogenicity/virulence testing. Also, the ability of the non-pathogenic Fusarium for production of mycotoxins should be tested. Finally, the importance of application of non-pathogenic Fusarium over chemical pesticides is far outreaching and comparatively more beneficial.