| Results and Discussion Except for AUS15157, which appeared to be tetraploid (all the plants studied had 2n=28 chromosomes), most of the plants in the lines studied were hexaploids (2n=42) (Table 1). Most of the hexaploid plants of the lines AUS15910, AUS15915 and AUS15916 produced supernumerary spikelets. The progeny of supernumerary spikelet plants of AUS 15910possessing 42 chromosomes have bred true for this character in subsequent glasshouse plantings. The head type of the plants of AUS17335 and AUS17336 could not be satisfactorily verified due to their very high vernalization and long photoperiod requirement (six weeks of vernalization at 4C and 18 hr photoperiod were tried with partial success in inducing heading). However, in experiments of PENNELL and HALLORAN (1984) these lines planted outdoors during the normal growing season displayed the supernumerary spikelet character consistently. Both these lines were isolated for branched-ear character from bread wheat and differ from normal wheats in two genes (KORIC 1973, 1978). There were some 43 and 41 chromosome plants in some lines (Table 1). These could be taken to be due to spontaneous variation in chromosome numbers which has been well documented for wheat (e.g. WORLAND 1981). The hexaploid plants which produced normal heads could be considered to have arisen from contamination either by cross pollination or accidental seed mixing. The above results and those of PENNELL and HALLORAN (1983) suggest that the genetic nature of the supernumerary spikelet character in the above lines is most likely different from that reported by SINGH and JOSHI(1983). Further cytogenetic studies of the supernumerary spikelet character to identify the chromosomal location of the genes controlling its expression, are in progress. References KORIC, S. 1973. Branching genes in Triticum aestivum. In Proceedings, 4th International Wheat Genetics Symposium, Columbia, Missouri, University of Missouri, pp. 283-288. KORIC, S. 1978. Triticum aestivum ramifera, new genetic resource. In Proceedings, 5th International Wheat Genetics Symposium, New Delhi, India, pp. 171-176. PENNELL, A. L. 1983. The genetics and physiology of aspects of growth and yield in wheat. M. Agr. Sc. Thesis, The University of Melbourne. PENNELL, A. L. and G. M. HALLORAN. 1983. Inheritance of supernumerary spikelets in wheat. Euphytica 32: 767-776. PENNELL, A. L. and G. M. HALLORAN. 1984. Influence of vernalization and photoperiod on supernumerary spikelet expression in wheat. Ann. Bot. 53: 821-831. SINGH, D. and B. C. JOSHI. 1983. Cytogenetics of branched spike in bread wheat. Wheat Inf. Serv., 56: 1-2. SWANMINATHAN, M. S., V. L. CHOPRA and G. R. K. SASTRY. 1966. Expression and stability of an induced mutation for ear branching in bread wheat. Current Science, 35: 91-92. WORLAND, A. J. 1981. Brigand offtypes. Annual Report, Plant Breeding Institute, Cambridge, pp. 69-70. |
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