TITLE:
In Vitro Screening of Cactus [Opuntia ficus-indicia (L.) Mill] Genotypes for Drought Tolerance
AUTHORS:
Berhan Mengesha, Firew Mekbib, Eyasu Abraha
KEYWORDS:
Callus Induction, Polyethylene Glycol (PEG 6000)
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.13,
September
16,
2016
ABSTRACT: Drought is one of the complex environmental factors
affecting growth and yield of crops in arid and semi-arid areas of the world.
In this context, this investigation was carried out to select drought tolerance
cactus genotypes under in vitro condition. An experiment was carried out at Laboratory of Mekelle Agricultural
Research Center, Northern Ethiopia. Six cactus pear genotypes namely, Gerao,
Keyih Beles,
Shenkor, Limo, Lemats Beles
and Suluhna were used. Areoles were used as explants in tissue culture. The
non-ionic water soluble polymer polyethylene glycol (PEG) of molecular weight
6000 was used as osmoticum to simulate water stress. In the first culture, the
MS medium was supplemented with (2, 4-D (4 mg/l) and BA (0.5 mg/l) for callus induction.
In all cultures MS medium was supplemented with 0, 10, 20 and 40 g/l polyethylene glycol
(PEG) and was solidified with 0.8% agar and 30 g of sucrose. Significant differences were observed
among the genotypes, PEG levels. In the first culture highest number of explants
initiated callus on medium supplemented with no PEG but had not shown
significant difference with 10 g/l
PEG. At 10 g/l
PEG, the callus induction frequency, callus fresh weight and plantlet
regeneration were recorded highest for Suluhna (83.3%, 5.5 g and 63.3%),
respectively. At 40 g/l
PEG, callus induction frequency, callus fresh weight and plantlet regeneration
were produced highest for Suluhna
(41.7%, 2.75 g and
45%), respectively but no significant difference with Gerao, Limo and Lemats Beles. However, Shenkor
and Keyih Beles were induced callus but
became reddish black within 35 days supplemented with 40 g/l PEG. Both shoot and
root production decreased with increased PEG level in the medium. At 40 g/l PEG in MS medium, the
highest shoot number was in Suluhna genotype (4.33) followed by Gerao (3.67).
The highest shoot length was in Suluhna (2.11 cm) with no significant difference with Gerao (2.02 cm). Root number (5.00 and
root length (1.41 cm)
were in the genotype Suluhna. Survival percentage of in vitro regenerated plantlets was
100% during hardening. By taking into consideration, all the growth parameter
tested revealed that Suluhna, Gerao, Limo and Lemats Beles showed better drought stress tolerance at the
highest level of PEG while Keyih Beles and Shenkor appeared to be drought sensitive
at the highest level of PEG.