| Continuous spontaneous crosses between Aegilops
cylindrica and Triticum aestivum T. RAJHATHY Genetics and Plant Breeding Research Institute, C. D. A., Ottawa, Canada The observation of speciation in nature, even in its early stage, is always an exciting experience. Although numerous spontaneous interspecific and intergeneric crosses are reported in literature, the following observation deserves attention because it has been taking place annually for a long time. In 1913, the Hungarian botanist A. Degen found a peculiar looking Aegilops on a Danube Island, St. Andrew, about 30 miles north of Budapest. In 1917 he described this form as a new species and gave it the name Aegilops Sancti-Andreae Deg. In 1954 the author made an excursion to the island with Mr. Z. Zsak, a former assistant of Dr. Degen. Plants fitting the description of Ae. Sancti-Andreae were easy to find along wheat fields but only in places where Aegilops cylindrica was growing close by, mainly in the ditches. Looking for seeds we found that the plants were sterile. This and the presence of Ae. cylindrica led to the supposition that the plants originated from spontaneous crosses between Ae. cylindrica and T. aestivum. This was later confirmed by a chromosome count of 2n=35. In a survey of approximately 300 plants, six seeds were found, four of which were small and shrivelled, the other two appearing normal. The small seeds did not germinate, but from the normal seeds two partially fertile plants were obtained. These originated from spontaneous backcrosses with wheat as the cytological examinations revealed. We visited the area again in 1955, and in 1956 to search for backcross derivatives and alloploids. The sporadic formation of alloploid seeds would be quite probable if the regularity and frequency of hybridization were considered; cultivation, however, would interfere with their survival. In 1956 we found three partially fertile hybrids but no alloploids. These were growing in the border of the wheat fields at a depth no greater than about 10'. The plants were normally harvested with the wheat thus giving the backcross derivatives only a very slim chance to survive. St. Andrew Island adjacent areas along the bend of the Danube seems to be a peculiar ecological niche which promotes speciation. In a number of genera species and lower taxa have been described from that area. |