II. 36. Presence of cer-soh conditions the synthesis of secondary alcohols in barley epicuticular wax.
S. Placing, C.G. Kannangara, J.D. Mikkelsen, D. Simpson, and P. Wettstein-Knowles, Department of Physiology, Carlsberg Laboratory, G1. Carlsberg Vej 10, DK-2500 Copenhagen Valby, and Institute of Genetics, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen K, Denmark. "R"
Epicuticular waxes are readily removed from barley cuticles. With the aid of thin layer chromatography (TLC), the component lipid classes can be separated. The most important wax classes in barley are the alkanes, esters, aldehydes, primary alcohols, free fatty acids, beta-diketones and hydroxy-beta-diketones. The latter two lipids are absent on leaf blades and awns. Waxes on these two organs can be distinguished in Foma, however, by the presence of secondary alcohols in the awn but not the leaf blade wax. Secondary alcohols are not present in awn wax of the closely related Bonus barley (von Wettstein-Knowles and Netting, 1976). The variety Foma is derived from the progeny of a cross between Ymer, a sister variety of Bonus, and Morgenrot (Hagberg et al., 1961 and 1962). Since the alkanes which are present in all barley waxes are precursors of secondary alcohols (see von Wettstein-Knowles, 1979), the present experiments were carried out to establish the origin of the capability of Foma awns to synthesize secondary alcohols as well as to determine their mode of inheritance.
Awn wax of three lines of Morgenrot (PI 328147, PI 361655 and CI 10378) obtained from the USDA at Beltsville, Maryland, U.S.A. were shown via TLC to contain secondary alcohols. They were equally prominent in the awn waxes of F1 plants from reciprocal crosses between Bonus and Foma. Among the 155 F2 piants from the Bonus (female) x Foma (male) cross, 126 had secondary alcohols while 29 lacked them. The 156 F2 plants from the reciprocal cross segregated 118 with secondary alcohols to 38 without. The results demonstrate that the ability of Foma awns to synthesize secondary alcohols is determined by the presence of a single allele originating in Morgenrot that behaves as a complete dominant. This allele has been designated cer-soh (von Wettstein-Knowles, 1979). Since the presence of cer-soh can not be detected visually, no further genetic experiments are planned.
Methods:
Prelabelled long, thin test tubes in racks were taken to the field. One well emerged spike from each plant was inserted awn end down into a tube with the aid of a glass funnel. Preliminary tests demonstrated that the same funnel could be used for all samples, and that handling the spikes with fingers did not introduce any contaminants which interferred with the present analyses. After returning to the laboratory, each tube was filled with chloroform and 10 to 15 sec. later the spike was removed. The samples were taken to dryness by blowing air over the tubes with a fan. The wax was taken up in a small volume of chloroform, and equal size aliquots were spotted on 20 x 20 cm glass plates coated with Silica gel H; 18 samples per plate. The plates were developed with benzene and the lipids visualized by spraying with Rhodamine-6-G.
References:
Hagberg, A. and G. Persson. 1962. Svalövs kornsorter. J. Swedish Seed Association 72:337-351.
Hagberg, A., K. Wiklund, F. Asander, T. Mansson and A. Wiberg. 1961. Korn. J. Swedish Seed Association 71:430-454.
Wettstein-Knowles, P. von. 1979. Genetics and biochemistry of plant epicuticular waxes. In Biochemistry and Physiology of Plant Lipids. Eds. L.A. Appelqvist and C. Liljenberg. Elsevier (in press).
Wettstein-Knowles, P. von and A.G. Netting. 1976. Composition of epicuticular waxes on barley spikes. Carlsberg Res. Commun. 41:225-235.