High-frequency Somatic Embryogenesis from Quiescent Seed Cotyledons of Cucumis melo Cultivars

Abstract

<jats:p>A protocol for high-frequency somatic embryogenesis in <jats:italic>Cucumis melo</jats:italic> L. was developed using `Male Sterile A147 as a model cultivar. Basal halves of quiescent seed cotyledons were cultured on embryo induction (EI) medium containing concentration ranges of the auxin 2,4-D and the cytokinins BA, Bin, TDZ, or 2iP before transfer to embryo development (ED) medium. Medium with 2,4-D at 5 mg·liter<jats:sup>-1</jats:sup> and TDZ at 0.1 mg·liter<jats:sup>-1</jats:sup> was superior, with 49% of explants responding and an average of 3.3 somatic embryos per explant (6.8 somatic embryos per responding explant). More explants produced embryos when incubated on EI medium for 1 or 2 weeks (30% and 33%) than for 3 or 4 weeks or with no induction. However, 2 weeks was 2.9 times better than 1 week in terms of number of embryos per explant. One week of initial culture in darkness, followed by a 16 hour light/8 hour dark photoperiod, produced more responding explants (26%) than two or more weeks in darkness or no dark period at all; but 1 and 2 weeks of darkness resulted in a similar number of embryos per explant (2.1 and 2.8). Sucrose concentration in EI and ED media had a highly significant effect on embryo induction and development. EI medium with 3% sucrose resulted in more embryogenic explants than EI medium with 1.5% or 6% sucrose. However, treatments with 3% sucrose in EI medium and 3% or 6% sucrose in ED medium produced significantly more embryos per explant (8.5 and 11.9) than other treatments. Treatments did not affect embryo induction directly and regeneration per se but, instead, frequency and efficiency of somatic embryo development. The optimal treatments were tested with 51 other commercial varieties. All varieties underwent somatic embryogenesis, exhibiting a response of 5% to 100% explant response and 0.1-20.2 embryos per explant. Chemical names used: N-(phenylmethyl)-lH-purin-6-amine (benzyladenine or BA); N-(2-furanylmethyl)-lH-purin-6-amine (kinetin or BIN); N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron or TDZ); N-(3-methyl-2-butenyl)-lH-purin-6-amine (2iP); (2,4-dichlorophenoxy) acetic acid (2,4-D).</jats:p>

Genotype and medium affect shoot regeneration of melon

“…The differences between our results and those previously published may be attributed to the different genotypes used. Variability in morphogenetic responses among genotypes and even between different seed lots of the same cultivar was also found by Orts et al (1987) and Gray et al (1993). Other factors, such as age and type of cultured explants, may influence the morphogenesis ability.…”

“…Moreno et al (1985) found that a combination of kinetin and indoleacetic acid stimulated plant regeneration, while Neidz et al (1989) found that BA was Cytokinins such as zeatin, 2-isopentenyladenine and TDZ were less effective for shoot differentiation from melon cotyledons than BA (Niedz et al 1989). Furthermore, a combination of BA and 2-isopentenyladenine was better than BA alone in stimulating regeneration from leaf explants of 'Pusa Sharbati' (Kathal et al 1988), whereas TDZ stimulated the production of more somatic embryos than BA, kinetin and 2-isopentenyladenine (Gray et al 1993). All genotypes tested in the present study produced shoot buds in the presence of BA alone.…”

Identification of tetraploid regenerants from cotyledons of diploid watermelon cultured in vitro

“…Differences in explant response among cultivars of the same species has been observed in cucumber, Cucumis sativus L . (Kim et al ., 1988), melon (Gray et al ., 1993 ;Niedz et al ., 1989), potato (Cardi et al ., 1993 ;M'Ribu & Veilleux, 1990), tomato 'Collective diameter of all 3 flexuous anthers per flower . Y Leaf length by width ratio ; obtained by dividing the leaf length by its width .…”

Somatic embryogenesis in Cucurbitaceae

“…Although systematic screenings of genotypes are rare, there is no doubt that genetic factors play a major role in somatic embryogenesis competence (Jelaska 1974;Malepszy & Nadolska-Orczyk 1983;Callebaut et al 1987;Colijn-Hooymans et al 1988a, b;Gray et al 1993;Oridate et al 1992). Nadolska- suggested a genetic determinism in the ability to regenerate somatic embryo-derived plants from cucumber (Cucumis sativus L.) leaf explants: the 'intermediately' and 'intensively' regenerating lines contained two pairs of dominant genes responsible for in vitro plant regeneration, characterized by complementary and probably additive interactions.…”