Improvement of Watermelon with Polyploids

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Cucurbit Genetics Cooperative Report 2:25-26 (article 15) 1979

0. J. Eigsti
17305 SR4, R. R. 1, Goshen, IN 46526

Numerous polyploid species are important crops that show superiority over their diploid progenitors, and natural polyploid species exhibit a much wider range of adaptation than their related diploids (6). In both cases, the polyploids have attained a maximum fitness (2). The selective forces operating with crop species and the natural polyploids are not radically different; accordingly, the plant breeder should recognize the importance of these forces (2).

Comparisons were made between triploid hybrids and from the induced as well as the spontaneous tetraploids (5). In morphological characters and seed productivity, there were no significant differences between the two kinds of tetraploids or the performance of the different triploid hybrids. These observations are supported by a study of the dynamics of polyploid populations (12).

The use of colchicine opened a new opportunity for crop improvement (8). Such methods, in effect, speed up the process of evolution (2), A unique and notable application was made to watermelons with induced tetraploids and subsequent triploid hybridization (10).

First attempts to produce seedless watermelons originated at Michigan State University, combining colchicine and hormones (15). The colchicine treated plants were seedless and since this publication was made, it has been observed that the colchicine generation may be seedless. The concept to obtain seedless fruits with triploids began with the work of Prof. Kihara (10). His associates and others have used these methods, and all reports stress the fine quality of the triploid fruit (3, 4, 7, 11, 13, 14).

Difficulties with seed germination has retarded the expansion of triploid cultivation. In other cases,the lack of disease resistance was regarded as a serious obstacle. Disease resistance can be developed in the tetraploids and triploids (9). The seed germination problem can be solved and the tolerance to the serious diseases can be attained.

One tetraploid strain was propagated through twenty generations. Field populations provided natural selection and the surviving genotypes showed a gradual improvement with each generation. There was no attempt made to select the most disease resistant, the earliest, or the one plant superior to all others. Rather, the average and above average survived and these individuals gave the basic genetic material that was propagated. One should not select the most disease resistant without proper balance of other characters (1). After twenty generations, the tetraploid was improved and showed advantages over the early ones.

The first triploids showed excellent quality (7). At the same time, the first impression of triploids was not entirely favorable because ovules were equated with seeds and the vigor of triploids was lacking. The idea developed that it was impractical to produce seedless melons. The cost factor is given as another reason for impracticality, but this must be viewed in light of the success or failure to obtain a productive crop. Growers willing to modify procedures can and should consider triploid watermelon as a potentially valuable crop.

Literature Cited

  1. Andrus, C. F. 1953. Evaluation and use of disease resistance by vegetable breeders. Proc. Amer. Soc. Hort. Sci. 61:434-446.
  2. Andrus, C. F. 1963. Plant breeding systems. Euphytica 12:205-208.
  3. Andrus, C. F., V. S. Seshadri and P. C. Grimball. 1971. Production of seedless watermelons. USDA Tech. Bul. 1425.
  4. Anghel, L. 1975. Pepeni fara Seminte. Fac. de Biol. U. d Bucuresti. Bucuresti, Rumania. 113 pp.
  5. Dyutin, K. E. 1974. Spontaneous tetraploids of watermelon Citrullus lanatus (Thunb) Mansf. All Union Research Institute for Melon Cultivation on Irrigated Lands. Kamyzyag. 416306. USSR.
  6. Eigsti, 0. J. 1957. Induced polyploidy. Amer. Jour. Bot. 44:272-279.
  7. Eigsti, O. J. 1971. About our cover. HortScience 6:2.
  8. Eigsti, O. J. and P. Dustin, Jr. 1955. Colchicine. Iowa State Press, Ames, Iowa. 470 pp.
  9. Henderson, Warren R. and S. F, Jenkins, Jr. 1977. Resistance to anthracnose in diploid and polyploid watermelons. J. Amer. Soc. Hort. Sci. 102:693-695.
  10. Kihara, H. 1951. Triploid watermelons. Proc. Amer. Soc. Hort. Sci. 58:217-230.
  11. Matsumoto, K. 1958. Seedless watermelons. Japan Assoc. for Polyploid Crops. Kyoto Univ. Kyoto, Japan. 4 pp.
  12. Savchenko, V. K. 1978. Dynamics of the genetic structure of polyploid populations. XIVth Internat. Gen. Cong. Moscow, USSR. Abst. Part II, Ses. C 26, p. 153.
  13. Shimotsuma, M. 1961. A survey of seedless watermelon breeding in Japan. Kihara Inst. for Biol. Res. Seiken Ziho. 12:75-84.
  14. Shimotsuma, M. 1965. A survey of seedless watermelon breeding and its extension in Taiwan. Kihara Inst. for Biol. Res. Seiken Ziho 17:46-54.
  15. Wong, C. Y. 1941. Chemically induced parthenocarpy in certain horticultural plants with special reference to watermelon. Bot. Gaz. 103:64-86.