Cuticular waxes in the tribe Triticinae

S.B. BHOSALE and V.P. PATIL

M.A.C.S. Research Institute, Poona 411004, India

In the tribe Triticinae, species belonging to Triticum, Secale, Hordeum, Avena and other genera often show varietal differences in respect of presence or absence of cuticular waxes in the form of powdery white, "waxy bloom". This character serves as a marker for varietal characterisation. By reducing transpiration, it contributes to drought resistance (FRUWIRTH 1923; HALL and JONES 1961). This waxy coat also prevents or retards the germination of rust and other spores or prevents their entry through stomata, thus serving as one of the factors for rust resistance (COBB 1891; VAVILOV 1950). Thus this "waxy bloom" has practical importance. The authors are not aware of any data on chemical composition of these waxes. Data collected by us have been summarised in this preliminary note:

Material and Methods

Following seven species belonging to different genera of the tribe Triticinae were grown during 1975-75 and utilized for these studies:

1. T. durum var. Wells CI-13333 (2n=28)
2. T. durum var. MACS-9 (2n=28)
3. T. aestivum var. NI-747-19 (2n=42)
4. Secale cereale var. OD-182 (2n=14)
5. Triticale var. JNKV 67040 (2n=42)
6. Hordeum vulgare var. Hiproly (2n=14)
7. Avena sativa var. Rapida (2n=14)

Cuticular wax of the above was scrached by scalpel from (a) leaf sheaths, (b) peduncles, and (c) spikes at proper stage, scrappings collected in diethyl ether and separated by thin layer chromatography (TLC). The TLC plates were prepared from Silica gel 'G' (E. Merk) of 0.2 mm thickness and activated at 110C for half an hour. The components of cuticular wax were separated by using petrolium ether; diethyl ether; acetic acid (80:20:1 by volume) and visualised by iodine vapours. The chromatogram was compared with a standard chromatogram and the components identified. Confirmation of the results has been done by repeating the experiments thrice.

Results and Discussion

Qualitative estimation of different components of cuticular waxes of the above varieties has been summarised in the Table 1.

Wax deposition on cuticle is due to the excretion of the required precursors through the peripheral cell walls (LEE and PRIESTLEY 1924; MAZLIAK 1968). This deposition helps in avoiding spore germination through its physiological, biochemical or mechanical properties (JOSHI 1957). It will be seen from the above table that components of the cuticular waxes such as fatty acids are present in waxes from leaf sheath, peduncle and spike in all the seven types studied. Such constancy is also observed for triglycerides, except in waxes from leaf sheath (in var. Wells CI-13333) and peduncle (in var. MACS-9). Other components vary in their presence on different parts in these seven types. Thus there is constancy in certain components (fatty acids, triglycerides, methyl ester) on leaf sheath, peduncle and spike irrespective of the ploidy level. Constancy within species has also been observed for methyl esters, fatty acids and alcohols though other components vary in different parts even within the same species (T. durum). Except for the occurrence of methyl esters, monoglycerides on leaf sheath, fatty acids on peduncle and triglycerides on spike, the other components differ in their presence on other parts, e.g. leaf sheath wax components did not show presence of triglyceride in T. durum var. Wells, alcohol in MACS-9 and in oats, where as steroids were noticed only in T. aestivum var. NI-747-19 and in rye. Similar variations for peduncle and spike waxes have been noticed as shown in Table 1. Further qualitative and quantitative analysis is in progress at this Institute and will be reported in due course.

Authors are grateful to Dr. G.B. DEODIKAR, Director. M.A.C.S. Research Institute, Poona 4, for facilities and guidance during the course of this work. Grateful thanks are also due to Prof. D.S. DATAR for facilities and suggestions. This work has been carried out under the All India Coordinated Projects on Wheat and Fruits sponsored by the Indian Council of Agricultural Research, New Delhi.

Literature Cited

COBB, N.A. 1891. Agr. Gaz. N.S. Wales, 2: 493.

FRUWIRTH, C. 1923. Handbuch der Landwirtschaftlichen Pflanzenzuchtung Bd IV Auff. Berlin.

HALL, D.M. and R.L. JONES 1961. Nature Lond. 191: 95-96.

JOSHI, A.B. 1957. Indian J. Genet. 17: 305.

LEE, B. and J.H. PRIESTLEY. 1924 ANN. Bot. 38: 525-545.

MAZLIAK, P. 1968. 'Progress in Phytochemistry' (L. Reinhold and Y. Liwschitz eds) 1: 49-111, Interscience, New York.

VAVILOV, N.I. 1949/50. The Origin, Variations, Immunity and Breeding of Cultivated Plants. Chronica Botanica, p. 364.

(Received Aug. 2, 1976)