Nature 180: 612 (1957)
Successful Crossing in the Genus Lathyrus through Stylar Amputation.
A. J. S. Davies

Abstract

INTERSPECIFIC hybridization in the genus Lathyrus has been attempted by several workers with little success. Barker1 obtained viable, partially fertile hybrids from the cross L. hirsutus x L. odoratus. Taylor2 claimed to have produced seeds by crossing L. odoratus with L. pratensis reciprocally. It has not been possible to repeat this cross. Senn3 reported failure in 458 attempts at intercrossing seventeen species of Lathyrus and Pisum sativum. Marsden-Jones4 successfully crossed L. rotundifolius with L. tuberosus. In this Department viable seeds have been produced from the following crosses: L. cicera x L. sativus (Saw Lwin*), L. clymenum x L. ochrus (Saw Lwin*), L. clymenum x L. articulatusóreciprocally (Davies), L. articulatus x L. ochrus (Davies), L. hirsutus x L. odoratus (McWhirter*), L. odoratus x L. hirsutus (Davies), L. sylvestris x x (Ellis*).

The cross L. hirsutus x L. odoratus of Barker has been successfully repeated in this Department without difficulty. Some reciprocal crosses were attempted between 1951 and 1955 but were unsuccessful.

The reasons for failure in interspecific hybridization attempts have been discussed by Blakeslee5, and methods employed to overcome barriers to crossability have been reviewed by Maheshwari6. Lack of success in the cross L. odoratus x L. hirsutus could be due to the greater style-length of L. odoratus (10 mm.) as compared with L. hirsutus (4 mm.). Style-length differences contributed to the failure of interspecific crossing attempts in the genus Datura5.

A modification of the technique of Buchholz et al.7 involving complete amputation of the female parent style was used in crossing L. odoratus with L. hirsutus, and several hybrids were produced. The best results were obtained by pollination on the cut stump after all the style was removed, though after removal of 4 mm., 6 mm. and 8 mm. portions, fertilization did sometimes take place. Grafting L. hirsutus styles on to the ovaries of L. odoratus was successfully effected, but showed no advantage over direct pollination on the cut stump.

For routine crossing and to avoid emasculation damage, a modification of Doak's soda-straw method8 for crossing Gossypium was found to be useful. Pieces of the culms of various species of grass were fitted down over the styles of unopened flowers, excluding the anthers and with one end protruding from the keel. When the flower had opened pollen was pushed down the culm with a tightly fitting glass rod on to the stigmatic surface. This method may have wide application in work with other genera.

This work was undertaken during the tenure of an Agricultural Research Council Research Studentship.

A. J. S. DAVIES
Department of Botany, University of Manchester, Manchester 13. May 2.

References

  1. Barker, B. T. P., Gard. Chron., Ser. 3, 60, 156 (1916).
  2. Taylor, C. M., Gard. Chron., Ser. 3, 60, 146 (1916).
  3. Senn, H. A., Amer. J. Bot., 25, 67 (1938).
  4. Marsden-Jones, E. M., J. Roy. Hort. Soc., 45, xcii (1919).
  5. Blakeslee, A. F., Proc. Amer. Phil. Soc., 89, 561 (1945).
  6. Maheshwari, P., "An Introduction to the Embryology of the Angiosperms" (McGraw-Hill, 1950).
  7. Buchholz, J. T., et al., Bull. Torrey Bot. Club, 59, 109 (1932).
  8. Doak, C. C., J. Hered., 25, 201 (1934).

Pollinating with a tube was practised by Darwin (1866).

Pollinating on the stump of the severed style was pioneered by Reychler (1926).

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