**2.2** *Fusarium oxysporum*

*F. oxysporum* is soil-borne pathogen that survive in the soil for a long time in the form of chlamydospores, penetrates the roots and colonizes in xylem vessels, systemic appear as yellowing, wilting, and death in plants. *F. oxysporum* are saprophytic and able to grow and survive for long periods on organic matter in soil and in the rhizosphere of plant species [59]. Some strains of *F. oxysporum* are pathogenic on plant species causing wilt and responsible for severe damage on many economically important crops and show host specificity based on the plant species and plant cultivars. They are classified more than 120 *formae speciales* and races [58]. Some strains can penetrate roots, but do not invade the vascular system [60]. *F. oxysporum* strains are responsible for two types of symptoms, such as vascular wilting and rotting. Vascular wilt resulting in yellowing and wilting of the plant [61]. Rotting of root without reaching the vascular system is called basal rot, stem rot, crown, root rot and also affect storage organs such as bulbs, corms, tubers and rhizomes. The first rot reported on lupine was caused by *F. oxysporum*


#### **Table 1.**

*Fusarium species and their host causing diseases.*


#### **Table 2.**

*Important 'formae speciales (f.sp.)' and race of Fusarium oxysporum.*

f. sp. *radicis*-*lupini*. The term "*radicis*" can differentiate rot-producing strains from wilt-producing strains. The "*radicis*" name of the *forma specialis* to allow for identification of the type of symptoms. Some *formae speciales* such as *cepae*, *lilii*, and *opuntarium*, cause rotting but are not referred as *formae speciales* "*radicis*-host plant name. *F. oxysporum* causes disease on vanilla, described to as *forma specialis radicis-vanillae*. Two different *formae speciales* are causing two types of symptoms in tomato as the *forma specialis lycopersici* causing wilt and *radicis-lycopersici* causing rot, **Table 1** [62–66].
