| Hybrid seed set in wheat x Aegilops crosses
Murat OZGEN University of Ankara, Faculty of Agriculture Department of Field Crops, Ankara, Turkey The wild relatives of wheat represent a valuable source of genetic variability for wheat breeding and Aegilops species are the richest source of resistance among wheat relatives. Several attempts have been made to transfer desirable chromosomal elements from Aegilops species to wheat. However difficultes in obtaining F1 hybrids, low germination in hybrid seeds and sterility of F1 hybrids are main barries in wheat x Aegilops breeding programmes. In this study four commercialy grown common wheat cultivars (Yayla 305, 4/11, Kose 220/39, Surak 1593/51) and four durum wheat cultivars (Beyaziye, Cakmak 79, L-51, S. Bursa 7113) were crossed as female parents with seven different Aegilops species as shown in Table 1, 2. All Aegilops species were collected from native rangelands in different regions of Turkey, except Ae. squarrosa which was introduced. The parents were seeded on experimental plots at three different dates in fall 1979 in order to synchronize the flowering periods. Emasculation and pollination studies were made in the early morning between 7.00 to 10.00 A.M. emerging spikes of wheat were selected for emasculation. The uppermost and lowermost two spikelets were removed. Approximately one-third part of the glumes in spikelets left on the spikes were cut. The primary florets in each spikelet were emesculated and secondary floret in the middle was removed. Emasculated spikes were bagged with parchement bags and checked in the next morning. When the stigmas were fully receptive, mature anthers were taken from Aegilops just before the bursting of the pollen sacs, and at least one anther was carefully placed on each stigma in the wheat spikes. Pollinated spikes were bagged again. The spikes were harvested at maturity. Hybrid seed set was expressed as the percentage of hybrid seed to number of the florets emasculated, in each combination. Two months later all hybrid seeds were placed between the layers of blotter papers for a germination test under laboratory conditions. Germination percentages of hybrid seeds were recorded and root tips were excised. Chromosome counts, using root tips, were made for all seeds. Low percentages of hybrid seed set have frequently been recorded in wheat x Aegilops crossing studies (DOSBA & CAUDERON 1972; GOTSOV & PANAYOTOV 1972; VARDI 1973; KASCHIRI 1974; MAMMADOV 1976). In our studies, however, clearly higher seed set was obtained (Table 1, 2) and chromosome countings also verified that all seeds were hybrid. The mean seed sets were 18.4% and 23.9% respectively in common wheat x Aegilops and durum wheat x Aegilops crosses. The highest seed set values were obtained in common and durum wheat x Ae. triuncialis combinations. |
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