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Wheat Information Service
Number 81:20-21 (1995)

Triticum aestivum -Triticum araraticum hybrids and their cytology

J. 8. Bijral and T. It Sharma

SKUAST, Regional Agricultural Recearch Station, R S. Pura 181102 India

Triticum araraticum (wild form of Triticum timopheevi, 2n=4x=28,AAGG) has been considered a valuable source of resistance to a number of wheat (Triticum aestivum, 2n=6x=42, AABBDD) pathogens, particularly Puccinia graminis tritici, P. recondite tritici, Erysiphe graminis tritici and Tilletia species (McIntosh and Gyarfas 1971). However, poor crossability of T. araraticum with cultivated wheat is the main barrier which precludes the transfer of resistance gene(s) from the former to the latter species. Consequently, there are relatively few reports on the successful transfer of disease resistance from T. araraticum to common wheat (Allard and Shands 1954; Watson and Luig 1968; McIntosh and Gyarfas 1971).

In order to transfer useful genes from T. araraticum to common wheat, three wheat cvs. Chinese Spring (ph1b mutant), C 306 and HB 208 were crossed as females with T. araraticum (Acc. No. 4697) under field conditions. Embryo culture or hormone application was not employed and the crossed seed were harvested at maturity. For meiotic studies, the spikes of the hybrids were fixed in aceto-alcohol (1:3 vlv) for 24 hours and then stored in 70% alcohol. The anthers were squashed in 2% acetocarmine and examined for metaphase-1 chromosome relationships.

The number of florets pollinated for the three crosses, viz., ph1b mutant x T. araraticum, C 306 x T. araraticum and HB 208 x T. araraticum (hereafter Hy-1, Hy-2 and Hy-3, respectively) were 40, 85 and 88, respectively and the per cent seed set 37.5, 84.8 and 31.6, respectively. Depending on the crossing directions and wheat genotypes with or without kr1 gene, seed set ranging from 8.8 to 84.0% has also been reported by Farshadfar et al. (1994).

Hybrid plants derived from the three interspecific crosses were partially fertile and there were 8.0, 1.2 and 3.0 weds per spike in Hy-1, Hy-2 and Hy-3, respectively. The pollination of over 85 florets of Hy-3 with wheat cv. RSP 122 produced 8 BC1 seeds. The percentage germination of F2/BC1 seeds of Hy-1, Hy-2 and Hy-3, and that of Hy-3 x RSP 122 was 13.3, 6.6, 8.0 and 12.5, respectively.

While Hy-3 and its backcross with RSP 122 await cytological analysis, the data of meiotic chromosome pairing' pertaining to Hy-1 and Hy-2 are presented in Table 1. The pentaploid hybrids (2n=5x=35, ABDAG) originating from ph1b mutant x T. araraticum cross combination (Hy-1) showed univalents and bivalents without multivalent formation. While number' of univalents and bivalents ranged from 17- 21 and 7 - 9, respectively, the mean bivalent frequency was 7.9 per cell.

Hy-2, on the other hand, was characterized by the formation of 28.1 univalents, 8.3 bivalents and 0.03 trivalents per cell. Of the bivalents, 44.0% were ring and 56.0% rod configurations. Trivalent association was recorded in one cell (3.4%) only. Increased level of chromosome pairing in Hy-1 as compared with Hy-2 could be due. to the absence of Ph gene.

Acknowledgements

Our thanks are due to Dr. G. S. Sethi, HPKV, Palampur and Dr. H. S. Dhaliwal, PAU-Ludhiana for kindly providing seeds of Chinese Spring (ph1b mutant) and T. araraticum (Acc. No.4697), respectively.

References

Allard RW and Shands RG (1954) Inheritance of resistance to stem rust and powdery mildew in stable spring wheats derived from Triticum timopheevi. Phytopathology 44: 226-274.

Parshadfar M, Molnar-Lang M and Sutka, J (1994) The crossability of different wheat (Triticum aestivum L.) genotypes with Triticum timopheevi Zhuk under two types of conditions. Cereal Res Comm 22: 15-20.

McIntosh RA and Gyarfas J (1971) Triticum timopheevi as a source of resistance to wheat rust. Z Pflanzenzuchtg 66: 240-248.

Watson IA and Luig NH (1958) Timvera-A Steinwedel x Triticum timopheevi derivative. Agron J 50: 644.

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