University of California

Pollination and parthenocarpy in the production of Bartlett pears in California


W. H. Griggs
Ben T. Iwakiri

Authors Affiliations

W. H. Griggs was Associate Professor of Pomology and Associate in the Experiment Station; Ben T. Iwakiri was Senior Laboratory Technician in the Experiment Station.

Publication Information

Hilgardia 22(19):643-678. DOI:10.3733/hilg.v22n19p643. April 1954.

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CALIFORNIA has over 37,000 acres of Bartletts. Experiment station workers in the state have since 1918 recommended interplanting pollinizers for this variety. In spite of this, most of the Bartlett orchards are now in solid blocks. Pollinizing varieties have been grafted over, and new plantings are almost invariably solidly to Bartletts. Only a few Bartlett growers make any effort to provide honey bees during the blossoming period. The question arises, therefore, as to what accounts for the high yields of a self-sterile variety planted in solid blocks.

This report covers a five-year study and shows that the Bartlett pear, though nearly self-sterile, is self-fruitful in most California orchards because of the production of parthenocarpic fruit. Vegetative parthenocarpy was responsible for most of the seedless fruit produced. Stimulative parthenocarpy due to self-pollination did not give significantly greater fruit sets than those effected by vegetative parthenocarpy alone.

Parthenocarpy means development of the edible fruit without fertilization. Parthenocarpic fruits are seedless. They have been divided into two types—vegetative and stimulative. Vegetative parthenocarpy implies that the fruit developed without pollination, while stimulative parthenocarpy indicates that they developed as a result of the stimulus of pollination.

Literature Cited

Cummings M. B., Jenkins E. W., Dunning R. G. Sterility in pears. Vermont Agr. Exp. Sta. Bul. 1936. p.408.

Detar J. E., Griggs W. H., Crane J. C. The effect of growth-regulating chemicals applied during the bloom period on the subsequent set of Bartlett pears. Proc. Amer. Soc. Hort. Sci. 1950. 55:137-139.

Dwyer R. E. P., Bowman F. T. Pollination of Williams (Bartlett) pear in New South Wales 1938. Dept. of Agr. New South Wales. Sci. Bul. 62

Flemion Florence. A rapid method for determining the viability of dormant seeds. Contrib. Boyce Thompson Inst. 1938. 9:339-351.

Fletcher S. W. Pollination of Bartlett and Kieffer pears 1911. Annual Report of the Virginia Polytechnic Inst. Agri. Exp. Sta. 1909 and 1910. 213-224

Florin E. H. Pollination of pears. Contrib. from the Swedish Permanent Comm. on Orchard Res. 1925. 5:1-39.

Gardner V. R. Basic horticulture. 1951. New York: The Macmillan Co.

Gourley J. H., Howlett F. S. Modern fruit production. 1947. New York: The Macmillan Co.

Griggs W. H., Iwakiri B. T., Detar J. E. The effect of 2,4,5-trichlorophenoxypropionic acid applied during the bloom period on the fruit set of several pear varieties and on the shape, size, stem length, seed content, and storage of Bartlett pears. Proc. Amer. Soc. Hort. Sci. 1951. 58:37-45.

Griggs W. H., Vansell George H. The use of bee-collected pollen in artificial pollination of deciduous fruits. Proc. Amer. Soc. Hort. Sci. 1949. 54:118-124.

Hooper C. H. Pollination of fruits. Jour. of the Ministry of Agr. 1921. 28:124-133.

Kamlah H. Untersuchungen uber die befruchtungsverhaltnisse bei Kirschen- und Birnensorten. Gartenbauwissenschaft. 1928. 1:10-45.

Kraus E. J., Kraybill H. R. Vegetation and reproduction with special reference to the tomato. Oregon Agr. Exp. Sta. Bul. 1918. p.149.

Luce W. A., Morris O. M. Pollination of deciduous fruits. Washington Agr. Exp. Sta. Bul. 1928. p.223.

Macdaniels L. H., Heinicke A. J. Pollination and other factors affecting the set of fruit, with special reference to the apple. 1929. Ithaca, N. Y.: Cornell Univ. Agr. Exp. Sta. Bul. 497

Marshall R. E., Johnston Stanley, Hootman H. D., Wells H. M. Pollination of orchard fruits in Michigan. Michigan Agr. Exp. Sta. Spec. Bul. 1929. p.188.

Middlebrooke W. J. Pollination of fruit trees. Observations and experiments from 1904-1912. Jour. of the Board of Agr. 1915. 22:418-433.

Murneek A. E. Plant growth-regulators during fertilization and post-fertilization periods. Proc. Amer. Soc. Hort. Sci. 1952. 59:207-217.

Noll F. Fruchtbildung ohne vorausgegangene Bestaubung (Parthenokarpie) bei der Gurke. Sitzber. niederrhein, Ges. nat. Heilk., Bonn. 1902. pp.149-162.

Overholser E. L., Latimer L. P. The cold storage of pears. California Agr. Exp. Sta. Bul. 1924. p.377. http://archive.org/details/coldstorageofpea377over

Rawes A. N. Pollination in orchards (IX). Jour of the Royal Hort. Soc. 1933. 58:288-295.

Reinecke O. S. H. Field and laboratory studies of the pollination requirements of varieties of deciduous fruit trees grown in South Africa 1930a. Union of South Africa. Stellenbosch-Elsenburg College of Agr. Sci. Bul. 9

Reinecke O. S. H. The relation of seed formation to fruit development of the pear. South African Jour. of Sci. 1930b. 27:303-309.

Robinson A. V. The effect of varying seed content on the composition of the Williams pear. Dept. of Agr. New South Wales, Sci. Bul. No. 1938. 62:47-58.

Snedecor George W. Statistical methods. 1946. Ames, Iowa: The Collegiate Press, Inc.

Tufts W. P. Pollination of the Bartlett pear. California Agr. Exp. Sta. Bul. 1919. p.307. http://archive.org/details/pollinationofbar307tuft

Tufts W. P., Hansen C. J. Variations in shape of Bartlett pears. Proc. Amer. Soc. Hort. Sci. 1931. 28:627-633.

Tufts W. P., Hansen C. J. Xenia and metaxenia in the Bartlett pear. Proc. Amer. Soc. Hort. Sci. 1933. 30:134-139.

Tufts W. P., Philp G. L. Pear pollination. California Agr. Exp. Sta. Bul. 1923. p.373.

Waite M. B. The pollination of pear flowers. U. S. Dept. of Agr. Div. of Veg. Path. Bul. 1894. p.5.

Waite M. B. Pollination of pomaceous fruits. U. S. Dept. of Agr. Yearbook of Agr. 1898. pp.167-180.

Weldon George P. Pear growing in California. California State Commission of Hort. 1918. VII(5):223-410. No

Wellington Richard. Present status of fruit pollination studies in the U. S. and Canada 1930. Proc. 9th Internat. Hort. Cong. (London) 297-304

Wellington Richard, Stout A. B., Einset Olav, Van Alstyne L. M. Pollination of fruit trees. New York State Agr. Exp. Sta. (Geneva) Bul. 1929. p.577.

Griggs W, Iwakiri B. 1954. Pollination and parthenocarpy in the production of Bartlett pears in California. Hilgardia 22(19):643-678. DOI:10.3733/hilg.v22n19p643
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