Micropropagation of Cashew (Anacardium occidentale L.)

Micropropagation work in cashew has been initiated first by Philip (1984) and reported direct plantlet regeneration from mature cotyledonary segments. Shoot bud proliferation on double phase medium (Lievens et al., 1989) and shoot multiplication in cotyledonary nodal segments of cashew seedlings have also been reported (D’Silva & D’Souza, 1992). Although shoot multiplication was possible but rooting was limited and hence in vitro rooting using Agrobacterium rhizogenes was reported by Das et al. (1996). Boggetti et al. (1999) and Mneney and Mantell (2002) have also attempted micropropagation in cashew. Thimmappaiah and Shirly (1999) have been able to regenerate cashew completely using explants from juvenile source and the protocol standardized in our laboratory is described in this chapter. Our success with regeneration from explants of mature tree source has been limited owing to poor growth, elongation and rooting of shoots (Thimmappaiah et al., 2002a). Micrografting as a technique to rejuvenate cashew and overcome rooting has also been described (Thimmappaiah et al., 2002b). Earlier attempts on micrografting in cashew were reported by Mantell et al. (1997) and Ramanayake and Kovoor (1999).

Regeneration of cashew through embryogenesis from cotyledon (Hegde et al., 1994; Jha, 1988; Sy et al., 1991), immature embryos (Cardoza & D’Souza, 2000; Gogate & Nadgauda, 2003) and nucellus (Ananthakrishnan et al., 1999; Gogte & Nadgauda, 2000; Cardoza & D’Souza, 2002; Shirly & Thimmappaiah, 2005) have been reported but complete regeneration and establishment of plantlets are yet to be achieved.