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Wheat Information Service
Number 84: 51-52 (1997)
Research information

Morpho-cytogenetics of Triticum aestivum L. x Aegilops speltoides Tausch. hybrids

J. S. Bijral Kuldip Singh and T .R. Sharma

SKUAST, Regional Agriculture Research Station, R.S.Pura - 181 102, India


The grain yield of wheat is directly related to the length of the growing season and the grain filling period. High temperature during the second fortnight of April especially in the North Western plains of India leads to grain shrivelling and significant reduction in grain yield. Aegilops speltoides Tausch. (2n=2x=14, SS), a wild species, is highly tolerant to high temperature particularly during the grain filling period. Due to relatively much longer photoperiod requirements, Ae. speltoides flowers during the second week of May and is found to set seed in the first fortnight of June when the temperature is usually above 40C. And the harvested seed is normal and plump. Additionally, Ae. speltoides is highly resistant to stem rust.

With a view to incorporate desirable traits of Ae. speltoides and more specifically high temperature tolerance into the bread wheat, interspecific hybrids between T. aestivum (ph1b mutant cv. Chinese Spring) and Ae. speltoides (Ace. No. 3808) were produced. All the hybrid plants were completely male sterile and resembled T. aestivum more closely than Ae. speltoides in general morphological traits. The Fl hybrids, however, exhibited much profuse tillering, had pigmented auricles and their terminal spikelets showed pronounced awning. Auricle pigmentation in conjunction with profuse tillering ability and characteristic awning indicated the expression of Ae. speltoides gene(s) in the cytoplasmic background of cultivated wheat. The mean chromosome pairing per pollen mother cell (PMC) was 6.82 bivalents (predominantly ring) + 0.9 bivalents + 0.26 quadrivalents + 10.3 univalents. The maximum chromosome pairing recorded was 12 bivalents (11 ring + 1 rod) + 4 univalents.

Since Chinese Spring is a poor agronomic cultivar, the Fl hybrids were topcrossed (as females) to T. turgidum ssp. dicoccoides (Ace. No. 4637) and VL 777, a bread wheat cultivar with good agronomic background. The seed set on topcrossing the allotetraploid Fl hybrids to the tetraploid and hexaploid wheats was 5% and 3.5%, resdectively which also confirmed the partial fertility (female) of the Triticum- Aegilops Fl hybrids.

Gene transfers from the alien chromosomes into the genomes of the cultivated species are usually achieved through rare recombinational events or through radiation-induced translocations. Alternatively, when the Fl hybrids are completely sterile, efforts are made to achieve gene transfer across Fl sterility barriers by producing monosomic alien addition lines (MAALs).

MAALs have primarily been produced and extensively studied in the polypoid species. Recently, such lines have also been developed in cultivated rice, a diploid species. The alien addition line technique was employed for transferring leaf rust resistance from Ae. umbellulata to hexaploid wheat (Sears 1956), stem rust resistance from Agropyron elongatum to hexaploid wheat (Knott 1961) and mildew resistance from Avena barbata into hexaploid oat (sung and Thomas 1978). Similarly, Jena and Khush (1989) transferred several genes including those for resistance to BPH and WBPH from Oryza officinalis into O. saliva.

The successful production of topcross seeds in the present investigation also opens up the possibility of producing alien addition lines of specific Ae. speltoides chromosomes for transferring useful traits especially higt temperature resistance from Ae. speltoides into the cultivated wheat. Efforts to develop such monosomic alien addition lines are underway.

Acknowledgments

Our thanks are due to Dr. H.S. Dhaliwal, Director, Biotechnology Centre, PAU, Ludhiana for kindly providing the seed of Ae. speltoides (Ace. No. 3808).

References

Aung T and Thomas H (1978) The structure and breeding behaviour of a translocation involving the transfer of mildew resistance from Auena. barbata Pott. into cultivated oat. Euphytica, 27: 731-739.

Jena KK and Khush GS (1989) Monosomic alien addition lines of rice: Production, morphology, cytology, and breeding behaviour. Genome 32: 449-455.

Knott DR (1961) The inheritance of rust resistance VI. The transfer of stem rust resistance from Agropyron elongatum to common wheat. Can J Plant Sci 41:109-125

Sears ER (1956) The transfer of leaf rust resistance from Aegilops umbellulata to wheat. Brookhaven Symp Biol 9: 1-22.

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