The aim of our research was development of improved breeding material through intraspecific hybridization, crossing T durum with T aestivum and investigation ofthe following theoretical and practical issues: Effective fertilization, various patterns and periods of pollination, determination of the mechanism of reciprocal crossing; Germination of hybrid grains, seed ability capacity, investigation of winter-hardiness and vitality characteristics of hybrid plants A certain part of experimental work was carried out at research base of Georgian RI of Agriculture, located at Mukhrani-Saguramo Plain. The following wheat varieties were used in crosses: population of local origin "Shavpkha" and breed developed varieties "Mameuli" "Dilikauri" " Jinvali" "Bezostaia 1 ", prospective varieties of bread wheat " Almasi" and "Vardzia". The best yield ofhybrid grains at reciprocal crossing in intraspecific hybridization is produced in cases when from 22,5 % to 45 % of durum wheat is used as a female lines with its 19,0-29,9% share in inverse combination. Pollination was carried out by the methods of open pollination, controlled open pollination and obligatory pollination. Well-developed plants were selected for crossing. Emasculation was carried out in the morning hours in selected maternal forms with the 2/3 of spike protrusion from vagina. 5 spikes with 20 flowers per spike were emasculated in each hybrid combination. The emasculated plants were isolated. Total12 000 flowers were emasculated during2001-2003. 24 hybrid combinations have been produced. Crossing of early maturing and late maturing forms of wheat is the important scope of interspecific breeding. The aim of our investigation was to determine on which day following the flower emasculation the stigma becomes most receptive to fertilization, when does the stigma reach the peak of physiological activity and how long after emasculation does stigma retain its vitality. Pollination was carried out every day starting from the 2nd and until18th day of emasculation. The best yield of hybrid grains was received at pollination on the 3rd day of emasculation. In an open field environment emasculated flowers of durum and bread wheat retain vitality for 12 days, therefore crossing of early and late forms is possible. Early maternal forms should be selected for the late pollination. The tests proved that the germination capacity Of hybrid grains is influenced by the female form of the hybrid combination. The tests showed that in cases when the durum wheat is used as a mother form the hybrid grain germination capacity in F generation is lower compared to parents, not exceeding 19, 1-38,4%, while when the female is the bread wheat the hybrids are of higher vitality and the germination rate reaches 33,4-58,4 %. Though the seed setting capacity in such combinations is lower, the vitality of the hybrid generation is higher. Thus, investigation of the hybrid grain vitality in intrespecific crosses of durum and bread wheat ascertained the association between the seed setting capacity of hybrid grains and their germination capacity. At the high seed setting rate their germi- nation capacity is lower and inversely, hybrid grain vitality is high when the bread wheat is used as a mother form. The one of the aims of interspecific hybridization of bread and durum wheat was the development of hybrid forms with the improved over-wintering capacity pertaining to bread wheat. The spring growth habit of durum wheat, its "vernality" should be partially modified in autumn. This was assessed by a five-score scale. Winter-hardiness of hybrid combinations produced through crossing of T -durum and T - aestivum averaged that of the parents, over- balancing the durum wheat and falling behind the bread wheat. Analyses of winter-hardiness of the first generation hybrid plants ascertained that winter- hardiness of the hybrid combinations is better than in durum wheat and approaching that of the bread wheat varieties. Heterosis was observed in cases when both parents were the winter forms and also when the bread wheat varieties of comparatively high winter tolerance were selected for the mother forms.

English

0407|AGRIS 0401|AL-Wheat Program

Juan Carlos Mendieta

CIMMYT Publications Collection