Cucurbit Genetics Cooperative Report 7:41-42 (article 18) 1984

Climacteric and Nonclimacteric Ripening in Cucumis melo

Stephen Kendall and Timothy J. Ng

University of Maryland, College Park, MD 20742

Many diverse fruit types exist among cultivated genotypes of Cucumis melo. Netted muskmelons and honeydews have been reported to be climacteric, but nonclimacteric genotypes of C. melo have also been reported (1). In experiments spanning a 3 year period, we have found that 'Golden Beauty Casaba' (GBC) and C2, a casaba-type breeding line obtained from the Texas A&M Agricultural Experiment Station, are nonclimacteric in their ripening behavior. As the presence and degree of the climacteric may affect storage life, we initiated studies to investigate this phenomenon.

Crosses were made between several genotypes of C. melo. 'Perlita' (PER), a cultivar with good shipping quality, and MD63- 53, a breeding line which lacks shipping quality, were the netted genotypes. Our experiments had previously shown that MD63-53 undergoes a climacteric prior to fruit abscission whereas PER experiences the climacteric rise after abscission. Table 1 presents data from an experiment dealing with field-grown melons harvested at physiological maturity (stem abscission for netted genotypes, softening of the blossom end for "non-slipping" genotypes) and stored at 10 C. Internal ethylene concentrations were determined by embedding hypodermic needles into the cavity of the fruit and sampling through septa at selected intervals. These results along with other experiments involving stored melons under a continuous air flow have confirmed that nonclimacteric genotypes of C. melo do exist and that hybrids between climacteric and nonclimacteric types experience a delayed climacteric when compared to the climacteric parent.

Table 1. Internal ethylene concentrations in genotypes of Cucumis melo after harvest when stored at 10 C.
Genotypez		Days from anthesis to maturity	Fruit weight (kg)	Internal C2H4 concentration (ppm)
				Day 1	Day 5	Day 7	Day 20
PER	Mean (n=23)	37.2	1.47	20.3	32.4y	-	-
	SD	1.2	0.30	5.8	13.9	-	-
C2	Mean (n=7)	44.2	2.52	1.3	1.6	5.4	-
	SD	2.7	0.65	0.2	0.4	1.0	-
GBC	Mean (n=9)	42.4	3.33	ndx	0.1	0.3	4.1
	SD	2.9	1.10	-	0.1	0.6	2.5
PER x MD	Mean (n=14)	34.1	1.78	23.1	35.6	-	-
	SD	0.9	0.31	14.6	34.9	-	-
PER x C2	Mean (n=10)	39.9	2.71	15.5	12.0	16.0	-
	SD	2.0	0.58	6.5	6.0	8.3	-
PER x GBC	Mean (n=7)	48.3	3.65	-	3.7	4.0	42.2
	SD	2.3	1.11	-	3.0	4.3	12.4
MD x PER	Mean (n=9)	33.7	1.57	17.4	14.5	-	-
	SD	1.0	0.34	8.0	5.3	-	-
MD x C2	Mean (n=5)	35.2	2.04	9.3	7.7	-	-
	SD	0.8	0.32	6.4	2.7	-	-

^zGenotype abbreviations are 'Perlita'(PER), 'Golden Beauty Casaba'(GBC), and MD63-53(MD).
^yThe last ethylene determination for each genotype was made after optimum horticultural maturity had been achieved.
^xEthylene was not present at a detectable level.

These differences in ripening patterns may be attributable to genetic differences in the fruit tissues, such as have been reported for ripening mutants of tomato (2). Oxygen availability to the fruit tissue may also be a factor since fruits of all nonclimacteric genotypes did not develop a net; the net in muskmelons is derived from the lenticels during fruit development and provides a channel for gaseous exchange with the surrounding atmosphere. Regardless of the physiological mode of action for this phenomenon, the implications remain that the use of nonclimacteric genotypes in breeding programs could be a valuable tool for genetically increasing the storage life of fruits of C. melo.

Literature Cited

1. Kitamura, T., T. Umemoto, and T. Iwata. 1975. Studies on the storage of melon fruits. II. Changes in respiration and ethylene production during ripening with reference to cultivars. J. Japan. Soc. Hort. Sci. 44:197-203.
2. Tigchelaar, E.C., W. B. McGlasson and R.W. Buescher. 1978. Genetic regulation of tomato fruit ripening. HortScience 13:508- 513.