**3. Plant-parasitic nematode problems on strawberry plants**

Several pathogens and pests cause damage to strawberry plants. Several plantparasitic nematodes damage strawberry plants that some feed on roots, others in foliar parts. Parasitic nematodes cause yield losses, crop size, and quality [35]. Many kinds of research have been conducted on Strawberry nematodes.

More than 4000 plant-parasitic nematodes are found on the earth [36]. In strawberry (*Fragaria x ananassa* Duch.) from soil and foliage, plant-parasitic nematodes are present in 10 genera and 15 species belonging to the order of Dorylaimida and Tylenchida [37]. *Xiphinema pachtaicum*, *Meloidogyne hapla*, *Aphelenchoides ritzemabosi*, *Criconema nutabile*, *Pratylenchus microdorus*, *Ditylenchus dipsaci*, *Longidorus caespiticola*, *Meloidogyne arenaria*, *Longidorus elongates*, *Pratylenchus penetrans*, *Helicotylenchus dihystera*, *Paratylenchus pseudoparietinus*, *Aphelenchoides besseyi*, *Tylenchorhynchus claytoni*, *Aphelenchoides fragariae*, are plant-parasitic nematodes in strawberry fields in the soil in Bulgaria [37]. *P. penetrans* is cause reddish-brown lesions on roots and increase fungus infections in the roots of strawberry [38]. *Aphelencoides fragariae*, *Aphelencoides ritzemabosi M. hapla*, *M. arenaria*, and *P. penetrans* species cause severe damage in strawberry fields and need to be controlled [37]. The virus vector nematodes: *Longidorus Criconemoides*, *Helicotylenchus Tylenchorhynchus* are frequently found in strawberry fields [37]. The root-knot nematodes, genus *Meloidogyne* Goeldi, are the most challenging in strawberry cultivation [39]. A sting nematode, *Belonolaimus longicaudatus,* is also one of the most damaging nematodes in strawberry plants [39–41]. *Aphelenchoides fragariae*, *M. hapla*, *Aphelenchoides besseyi*, *Aphelenchoides bicaudatus*, *Aphelenchoides ritzemabosi*, *Ditylenchus dipsaci*, *Longidorus elongatus*, *Meloidogyne javanica*, *Criconemella onoensis*, *Meloidogyne incognita*, *Helicotylenchus dihystera*, *Pratylenchus penetrans*, *Pratylenchus brachyurus*, *Xiphinema*, *Pratylenchus vulnus* and *Pratylenchus zeae* in Brazil [42–45].

Incidence and population density are *Aphelenchoides fragariae* (34–98), *Aphelenchoides ritzemabosi* (23–70), *Aphelenchoides besseyi* (8–11), and *Ditylenchus dipsaci* (8–16) in strawberry 15 g leaves of plant tissues [37]. Some major species of Strawberry in the USA are *M. hapla, A. besseyi, B. longicaudatus, A. fragariae,* and *P. penetrans* [39–41, 46]. Nematode existence incidence and density are vastly variable that *M. hapla* 55–125 nematodes/100 cm3 soil) and for *M. arenaria* (14-61nematodes/100 cm3 ) in Bulgaria [37].

*Meloidogyne* spp. is the utmost major species of plant-parasitic nematodes on strawberry plants in Egypt, and *Aphelenchoides* sp. may exceedingly decrease strawberry yields [35]. The second stage of *Meloidogyne* species is the infective stage of

nematodes and J2s penetrate plant roots, modify cell development, and cause root gall formation. During the nematode infection, nematode feeds on those cells termed giant cells, and females of root-knot nematodes develop within the galls [47–49]. Root-knot nematodes cause root galls in plants [47].

*Pratylenchus* species also damage strawberry plants. They are migratory nematodes that cause root lesions when they enter and migrate completely throughout the roots [49]. Nematodes cause damage to reducing roots, and nematodes absorb water and nutrients [49] and therefore decrease plant growth, shorten the crop cycle, decrease production, and cause leaf drop [39]. *Pratylenchus penetrans* is also a noteworthy nematode that is related to the occurrence of a disease that causes strawberry root rot [50, 51].

Some nematodes cause damage to others in the foliar part of strawberry, and they may be found in different densities in many countries. Plant-parasitic nematodes in the soil of strawberry plant may found as: *Helicotylenchus* (421.3 nematodes/100 cm3 of soil), *Scutellonema* (1.0 nematodes/100 cm3 of soil), *Meloidogyne* (3.9 nematodes/100 cm3 soil), Hemicycliophora (5.3 nematodes/100 cm3 soil), *Ditylenchus* (0.3 nematodes/100 cm3 soil), *Pratylenchus* (1.4 nematodes/100 cm3 soil), *Xiphinema* (0.4 nematodes/100 cm3 soil), *Trichodorus* (0.2 nematodes/100 cm3 soil) and *Mesocriconema* (0.2 nematodes/100 cm3 soil) in Brazil [52]. Root-knot nematodes: *M. javanica*, *M. arenaria*, *M. incognita, M. hapla,* and other nematodes: *A. fragariae, P. penetrans, Hemicycliophora* spp. and *D. dipsaci* are found in strawberry fields in Spain [53, 54]. *A. fragariae, D. dipsaci, Criconemoides morgensis, Hirschmanniella imamure, Meloidogyne arenaria, P. penetrans, H. dihystera, Tylenchorhynchus claytoni, Psilenchus hilarulus,* and *M. incognita* are found, but the root nematodes: *M. arenaria* and *M. incognita* are utmost common species among them in strawberry fields in Korea [55]. Similarly, the species of *Pratylenchus, Xiphinema, Helicotylenchus, Rotylenchus,* and *Ditylenchus* are associated with strawberries [56].

Some strawberry cultivars can be resistant or susceptible to nematode species. The cultivars: San Andreas, Monterey, Camino Real, Oso Grande, Aromas, and Albion) are resistant to *M. incognita, M. javanica, Pratylenchus zea,* and P*. brachyurus*. However, some strawberry cultivars, such as Camarosa are susceptible to *M. hapla* and *M. arenaria* [57].
