Cucurbit Genetics Cooperative Report 3:27-29 (article 15) 1980

In Vitro Callus and Shoot Induction from Hypocotyl and Peduncle of Muskmelon (Cucumis melo)

K. Abak and R. Dumas de Vaulx

Ankara Universitesi Ziraat Fakultesi, Bag-Bahce Kursusu, Diskapi-Ankara, Turkey (first author); Station d'Amelioration des Plantes Maraicheres, I.N.R.A., Domaine Saint Maurice, 84140 Montfavet-Avignon, France (second author)

In vitro propagation has been successful in some species of the Cucurbitaceae: axillary bud culture in watermelon (2) and shoot and root formation from callus in pumpkin (5). In Cucumis spp. callus and root formation have been obtained in cucumber (1) and chlorophyll formation on callus in muskmelon(3).

We report here that we have induced shoot formation from callus of muskmelon. Explants from hypocotyl and peduncle of two diploid Charentais lines have been cultivated on different culture media. Explants were sterilized with 10% calcium hypochlorite (plus Tween 20) and then washed three times in sterilized distilled water. Thin explant slices (1.5mm) were put on the culture medium in small plastic petri dishes.

Two different basal media have been used: one designated G (macro and microelements from Galun et a1. (4)) and the other one MS (macro and microelements from Murashige and Skoog (6)). Both were supplemented with the following vitamins and organic components: thiamin-HCl (0.55 mg/l), pyridoxin-HCl (0.55 mg/l), nicotinic acid (0.5 mg/l), glycine (1.5 mg/l), tryptophan (2.5 mg/l), and meso-Inositol (100.0 mg/l). Various concentrations of sucrose (10-90 g/l), difco-bacto agar (6-10 g/l), casein hydrolysate (0-0.4 g/l), and different combinations of growth regulators: indole acetic acid (IAA), naphthalene acetic acid (NAA), kinetin, benzylaminopurine (BAP), zeatin, and gibberellic acid (GA3) were tired. The cultures were incubated in a growth chamber at 26°C day temperature and 22°C night temperature with artificial light 12 hrs daily.

Callus has been initiated from hypocotyl explants from the basal end, and on both sections from peduncle explants on the different media tried. Similar results were obtained with both lines (Table 1).

Callus formation was obtained on G and MS media supplemented with 40 g/l sucrose, 7 g/l agar, 0.3 g/l casein hydrolysate (only for G), 2 mg/l kinetin, and 0.2 mg/l NAA, pH 5.6. On both media more than 250 mg callus weight were obtained within four weeks.

We tried to induce shoot regenerations from callus on several media: G and MS basal media supplemented with different sucrose, agar, NAA, and Kinetin concentrations (Table 1). Shoot regeneration was accomplished on MS medium supplemented with 30 g/l sucrose and 10 g/l agar (called MST). The optimal growth regulator concentrations were 0.2 g/l NAA and 0.2 or 0.02 mg/l kinetin. Regeneration was unsuccessful on G basal media at the different sucrose, agar, NAA, or kinetin concentrations tried.

The first shoots appeared two weeks after callus transfer. Later, several shoots with small leaves appeared from the same callus.

We have not yet succeeded in initiating rooting. However, on some media used for regenerations, we have notice adventitious root formation directly on callus but without shoot formation (media with high auxin and low cytokinin concentrations). These media and other are now under test for regeneration of complete plantlets.

Table 1. Callus growth and shoot regeneration of hypocotyl and peduncle explants of Cucumis melo on different media.

G Medium + 40 g/l sucrose + 7 g/l agar + 0.3 g/l casein hydrolysatez
NAA (mg/l)	Kinetin (mg/l)	Callus growthy	Transfer medium G or MST with NAA 0.2 mg/l, kinetin 0.2 mg/lz	Shoot regenerationx
0.00	0.00	0	-	-
			-	-
0.02	0.02	+	G	0
			MST	++
0.02	0.20	+	G	0
			MST	++
0.02	2.00	+++	G	0
			MST	++
0.20	0.02	++	G	0
			MST	++
0.20	0.20	++	G	0
			MST	++
0.20	2.00	+++	G	0
			MST	++

^z MST and G - see composition in text

^y Callus weight within four weeks
+ < 100 mg/explant
++ 100-200 mg/explant
+++ > 200 mg/explant

^x Shoot regeneration
0 none
+ low
++ high

Literature Cited

1. Alsop, W. R., W. W. Cure, G. F. Evans and R. L. Mott. 1978. Preliminary report on in vitro propagation of cucumber. Cucurbit Genetics Coop. Rpt. 1:1-2.
2. Barnes, L. R., F. D. Cochran, R. L. Mott and W. R. Henderson. 1978. Potential uses of micropropagation for cucurbits. Cucurbit Genetics Coop. Rpt. 1:21-22.
3. Fadia, V. P., and A. R. Mehta. 1976. Tissue culture studies on cucurbits: chlorophyll development in Cucumis callus cultures. Phytomorphology 26:170-175.
4. Galun, E., Y. Yung and A. Lang. 1963. Morphogenesis of floral buds of cucumber cultured in vitro. Developmental Biology 6:370-387.
5. Jelaska, S. 1974. Embryogenesis and organogenesis in pumpkin explants. Physiol. Plant. 31: 257-261.
6. Murashige, T. and F. Skoog. 1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant. 15:473-497.