**2. Etiology**

*Phytophthora capsici* belongs to the Phylum: Oomycota, Class: Oomycetes, Order: Peronosporales, and Family: Peronosporaceae (**Figure 1**). Under laboratory conditions, the phytopathogen can grow in culture media based on V8 juice [17, 18], carrot, tomato, and water agar. Although the growth pattern of the oomycete can be different between isolates, the shape of the colonies is generally rounded and whitish [19], standing out those with a slightly stellate pattern (**Figure 1A**). The phytopathogen characteristics are: elongated, coenocytic hyphae (**Figure 1B**); stretched cells with several nuclei [20], measuring between 3 and 8 μm wide [21]; oospores with a diameter between 25.6 and 52.4 μm (**Figure 1B**) [22]. Its sporangia (**Figure 1C**) are abundant and formed individually or branched, flaccid or closely spaced [21], mainly spherical (globose, ellipsoid and ovoid), pear-shaped (obpiriform and obturbinate), lemon (limoniform), and/or in some cases irregular (distorted) [19], measuring between 32.1 and 51.3 μm long and 23.3–37.1 μm wide [20]. The main pedicel has a length of 38.3 to 84.4 μm [22]. The zoospores released from the sporangia (**Figure 1D**) have a diameter between 5.84 and 11.3 μm [20]. Although resistance structures such as chlamydospores can also be formed by some *Phytophthora* species [21], it is not common in *P. capsici* [18].

Phytophthora capsici *on* Capsicum *Plants: A Destructive Pathogen in Chili and Pepper Crops DOI: http://dx.doi.org/10.5772/intechopen.104726*

### **Figure 1.**

*Morphological structures of* Phytophthora capsici*: A) Colony morphology after 14 d growth at 24 ± 3°C on potato dextrose agar; B) Coenocytic mycelium, and oospore; C) Papillate limoniform sporangia; D) Zospores inside and outside of sporangia. Cm: Coenocytic mycelium; O: Oospore; Z: Zoospores. Bars: 1 cm (A) and 10 μm (B-D). Source: Unpublished photographs from the authors.*
