Super-barbing - A new marker character in wheat

V.S. Prakasa RAO, M.D. BHAGWAT and V.P. PATIL

Maharashtra Association for the Cultivation of Science Law College Road, Poona 411 004, India

Earlier wheat workers have identified a large number of characters useful for varietal identification and studied their inheritance (reviewed by AUSEMUS, MCNEAL and SCHMIDT 1967). Among these are several awn characteristics like awn development, awn colour and awn barbing. Barbing of the awn is predominant in most of the wheats and is responsbile for the scabrid nature of the awns and results from the presence of uni-cellular thickwalled cells with fine points directed upwards. The base of the awns was almost smooth in durum wheats (PERCIVAL 1921). However, smooth-awned wheats have been described from Syria and Palestine (FLAKESBERGER 1929), from Spain (SANCHEZ-MONGE and VILLENA 1951), and from a line of the cross Marquis x Iumillo (SIGFUSSON 1929). In crosses with smooth-awned wheats SIGFUSSON (1933) reported cumulative factors respon barbing. Later KNOWLES (1943) identified a major gene and a minor gene for barbing in durum wheats. The major factor is responsible for usual roughness while the second factor when homozygous in the absence of major pair produces an intermediate type of barbing characterised by scattered barbs from tip to base.

A variant of the barbing was observed in the course of investigations in progress at this Institute, in a plant of the culture RT 838, derived from the F₅ generation of (T. dicoccum var. KDH x T. pyramidale) F₁₁ x T. durum var. Mx 0.16. In this type, apart from the regular barbing, additional felt-1ike outgrowths extend over the entire awn surface (Fig. 1B) and are so well marked as to be noticed even from a distance. Microscopic observations and cross sections have revealed no structural differences between the barbs described earlier and the additional outgrowths present in this culture. This character appears to be due to the abnormal elongation of the barbs. Because of the structural similarity of the trait to the barbing on wheat, this character has been named as Super-barbing and assigned the gene symbol B^s.

In order to study the inheritance of this character, true breeding lines have been isolated and crossed with the sib-culture with normal awns and also with other durum wheats with typical barbed awns. The results are presented in Table 1.

The super-barbing on F₁ plants was of a lesser intensity compared to the (super-barbed) parent suggesting thereby incomplete dominance of this character. In F₂ generation of the cross T. durum-N 59 x RT 838 (super-barb) apart from the super-barb and normal awned plants there were intermediate types characterised by sparcely elongated barbs. Hence, three classes - normal, intermediate and super-barb were made. In 9 populations studied there was no heterogeneity indicated and hence the data were pooled. The segregation indicated a close fit to 1:2:1 ratio. In the cross RT 838 (normal) x RT 838 (super-barb), however, the classification of barbed condition into super-barb and intermediate types was not possible due to poor development. Hence, only two classes - super-barb and normal were recorded. This also gave a good fit to 3:1 ratio.

Thus, the super-barbing trait appears to be governed by a single partially dominant gene. Further investigations regarding its relation to the smooth awned condition are in progress at this Institute.

The authors are grateful to Dr. G.B. DEODIKAR, Director, M.A.C.S. for guidance and facilities. The work was conducted as a part of the All India Coordinated Projects on Wheat and Fruit Improvement, of the I.C.A.R.

Literature Cited

PERCIVAL, J. 1921. The Wheat Plant. Duckworth and Company, London.

FLAKESBERGER, C. 1929. Bull. Appl. Bot. Genet and Pl. Breedding 22: 115.

SIGFUSSON, S.J. 1929. Scientific Agriculture 9: 533.

SIGFUSSON, S.J. 1933. ibid. 13: 185.

KNOWLES, P.F. 1943. Canad. J. Res. 21: 198.

SANCHEZ-MONGE, E. and L.M. VILLENA 1951. An. Estac. Exp. Aula. Dei. 2: 210.

AUSEMUS, E.R., F.H. MCNEAL and J.W. SCHMIDT 1967. In "Wheat and Wheat Improvement" Agronomy Monograph No.13, American Society of Argonomy, U.S.A.