Techniques of plant regeneration from cultured explants are prerequisites for genetic studies using tissue culture systems. Tomato has been found to be an ideal system for such studies (Shahin, 1984). Here we report the genotypic differences in shoot formation from cultured hypocotyl explants from five tomato cultivars popular in India.
One cm long hypocotyl explants from 10 day old seedlings of Lycopersicon esculentum Mill. cvs. Pusa Ruby, Roma, Best of All, Marglobe and Sioux were cultured on MS medium supplemented wtih BAP 2.25 mg/l and IAA 0.175 mg/l (Kartba et al., 1976). The cultures were incubated at 27 deg.C under constant illumination of about 1000 lux. The number of shoot initials in each explant was counted 30 days after inoculation under a dissection microscope. At least 12 explants from each variety were inoculated.
There was a distinct difference in shoot forming ability among the five genotypes tested (Table 1).
Table 1. Genotypic differences in shoot formation from cultured hypocotyl explants.
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Mean no. of shoot initials per
S. No. Variety explant, 30 d after incubation
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1 Pusa Ruby 14.0 +/- 2.76
2 Roma 1.8 +/- 0.40
3 Best of All 3.9 +/- 0.62
4 Marglobe 3.3 +/- 0.43
5 Sioux 5.0 +/- 0.53
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Pusa Ruby hypocotyls initiated the highest number of shoots, which is
significantly more than the mean number of shoots per explant in other
cultivars tested. Sioux, Best of All and Marglobe did not differ
significantly (P = 0.05% in Student's t-test) but Roma had significantly
fewer shoots when compared with the other four cultivars. Our observation
strengthens the view that in tomato it is important to standardize media and
culture conditions in each genotype to obtain optimum results in in vitro
experiments (Kurtz and Lineberger, 1983)References:
Kartha, K.K., O.L. Gamborg, J.P. Shyluk and F. Constable. 1976. Morphogenetic investigations in in vitro leaf culture of tomato (Lycopersicon esculentum Mill. cv. Starfire) and high frequency plant regeneration.Z.Pflanzenphysiol. 77:292-301.
Kurtz, S. and R.D. Lineberger. 1983. Genotypic differences in morphogenetic capacity of cultured elaf explants of tomato. J. Am. Soc. for Hort. Sci.108:710-714.
Shahin, E.A. 1984. Isolation and culture of protoplasts: Tomato. p. 370. In I.K. Vasil (ed.), Cell culture and somatic cell genetics of plants. Vol. I. Academic Press.