systems have been established to circumvent environmental stresses using
various genes. One of these genes code
for proteins that control the closing of the leaf stomata to prevent plant
evaporation and to overcome cellular dehydration Somerville
and Meyerowitz (2002), Bahieldin et al. (2005) and Oh et al. (2005). One of such
proteins in barley is called the late embryogenesis abundant 3 (LEA3), encoded by
Hordeum vulgaris abundant protein (HVA1) gene that has been proven to be
induced under ABA treatment Hong et al (1992)
and Dure et al. (1989).
They carry out
various functions like acting as hydrating buffers, sequestering ions, helping
in renaturation of proteins and acting as chemical chaperones (Dure 1993; Goday et al., 1994). It was found that
late embryogenesis abundant (LEA) protein gene HVA1 from Hordeum vulgares
L. upon transformation into rice confers salinity and drought tolerance to
transgenic plants (Xu et al., 1996).
The stress tolerant features (including salt and drought tolerance) of HVA1
gene transformed plants have further been proven in Basmati rice (Rohila et al., 2002) and Morusindica (Lal et al., 2008). In the same vein,
ectopic expression of PM2 from soybean; encoding for a type 3 LEA protein in
E.coli, results in salinity tolerance and therefore suggesting its probable
role in salinity tolerance in plants Liu et al.,
2010. Several other crops which were genetically transformed with
the barley HVA1 gene resulted in their increase in vegetative biomass and other
symptoms associated crop drought and/ or salt tolerance, tobacco (Lee et al., 2007), mulberry (Checker.,
et al 2012),maize ( Nguyen and Sticklen., 2013) and Oat (Maqbool et al., 2002).
Much work has
been carried out on callus induction and growth in potatoes (Solanum tuberosum
L.). This has resulted in a range of protocols and procedures being established
by researchers since tissue culture gained an importance in plant propagation,
conservation and breeding (Ahloowalia 1982; Wareh et al., 1989).
Previous researches showed that media used for
callus induction and growth depends on the genotypes Gonzalez et al 2001,
Alexeenko and Irkaeva (1998) pointed out that introduction of genes
effecting the structure and type of plant development into strawberry lines
also influenced callus formation and shoot inducing in vitro. This depicts
involvement of inheritance in callus growth.
In the last two decades, many transgenic
plants have been produced by using a range of transformation methods.
Callus is used
for most of these transformation methods such as particle gun (Decima et al 2010) and Agrobacterium
tumefaciens-mediated transformation (Stiekema et al., 1988) as well as
initiation of cell culture.