نشریه تحقیقات ژنتیک و اصلاح گیاهان مرتعی و جنگلی ایران
سال سوم شماره 1 (پیاپی 3، پاییز و زمستان 1379)

When and at which stage in Medics' flowers, pollan grains may grow and fertilize the pistile? How the fragile flowers of medics may be emasculated for inter and intra-specific hybridization, with high percentage of success? This study was carried out to answer these questions. To find the exact time of pollan maturation and their fertilability, the flowers of two species of medics, Medicago polymorpha and M.rigidula were visited at various sizes. And stages Pollan sacs were removed and cultured on agar based media. The best size of the flowers for emasculation before self fertilization was recognized for the two species. This size was about the stage before the tip of the standard petal past its calyx teeth. To emasculate the flowers on the mentioned stage, various density of ethilic alcohol, suction pump, surgical blade and fine/ needle were used. The best method to emasculate the flowers was opening the flowers through standard petal by surgical blade and removing the pollan sacs by suction pump or fine needle. After hybridization, to cover the fragile emasculated flowers to keep them fresh and moist, a glass tube was used, instead of paper bag, for 15 days at 25 degree of centigrade.

Successful tissue culture research and its practical application require a reliable culture procedure. During the tissue culture practices, the effects of genotype, medium composition and growth regulator (2,4-D) concentration on callus induction and growth were tested. A wild species of the genus Hordeum (Hordeum murinum), was tested beside the cultivated barley (Hordeum vulgare), for the study of genotypic variation in response to tissue culture. Matue seeds or immature embryos of both wild and cultivated barley species were used as---explants. Culture media contained MS macro- and micronutrients, or MSm (modified MS based salt), supplemented with 1.0 or 3.0 mg/l dichlorophenoxyacetic acid (2,4-D) as a growth regulator. On both of the test media, seedlings grown from seeds of both wild and cultivated barley produced callus. Averaging across genotype, the number of calli induced was greater in cultivated than wild barley. MS based medium gave faster callus induction than MSm based medium, although the medium formulations showed no difference for callus induction in tested genotypes. Comparisons across media revealed that callus growth in cultivated barley was greater on MS than MSm based medium. Furthermore, although little difference was observed in callus induction between the test concentrations of 2,4-D between two genotypes, calli obtained from cultivated barley grew faster in response to 3.0 than 1.0 mg/12,4-D on both media. Callus was also initiated from immature embryos of both test species on the medium containing MS based salts and 3 mg/l 2,4-D. Cultivated barley showed a higher efficiency of callus production (84.5%) than wild barley (77.7%). Also, calli derived .from both mature and immature embryos of cultivated barley showed prolonged growth, but the induced calli in wild barley ceased growth, turned brown and died after a few weeks.