CALLUS INDUCTION, PLANT-REGENERATION AND CHROMOSOMAL VARIATIONS IN BARLEY

Callus cultures were induced on mature embryo mesocotyl explants in Hordeum vulgare cv. Zafer-160. The callus induction ratio was 54% in Murashige-Skoog (MS) medium supplemented with 1 mg 1(-1) 2,4-dichlorophenoxyacetic acid (2,4-D). After transfer at 22, 45, 360, 540 days of culture to MS medium containing lower concentrations of 2,4-D (0.5, 0.1, 0.01 mg 1(-1)) or MS medium lacking 2,4-D, 45-day-old callus cultures showed somatic embryogenesis. The optimum 2,4-D concentration for somatic embryogenesis was 0.01 mg 1(-1). Callus cultures of 360 days showed regeneration via both somatic embryogenesis and organogenesis under the same conditions. Abnormalities in both number and structure of chromosomes increased with the age of calli. This phenomenon might be related to the loss of regeneration ability in 540-day-old calli. In-vitro regenerated plantlets gave rise to normal-looking plants after their transfer to soil. Regenerated plants had the normal diploid chromosome number (2n = 14) in their root tips

Yerli Arpa Varyetesi Zafer 160'da Husule Getirilen Suni Mutasyonlardan Tarımda Yararlanılması Yolunda Çalışmalar

Işınsal ve kimyasal mutajenlerle Zafer 160 arpasından elde edilen mutantların bazı tarımsal özellikleri incelenmiş, ülkemizin değişik bölgelerine adaptasyonları incelenmiştir

The 3' terminal sequence of the inosine monophosphate dehydrogenase gene encodes an active domain in the yeast Schizosaccharomyces pombe

The gua1 gene encoding inosine monophosphate dehydrogenase (IMPDH), which catalyses the first step in de novo biosynthesis of guanosine monophosphate (GMP), was cloned in the yeast Schizosaccharomyces pombe by functional complementation of a gua1ura4-D18 mutant strain from a S. pombe DNA genomic library. Complementation analysis revealed a 1.2 kb fragment which segregation analysis confirmed did not code for a suppressor gene. Only 446 nucleotides of the gua1 gene encoding the IMPDH C-terminal residues were found within this 1.2 kb sequence (GenBank, AJ293460). The comparison of this wild-type fragment with the same fragment from the gua1ura4-D18 mutant revealed that there was a point mutation at position 1261 (guanine -> adenine) from the 5' end, corresponding to the amino acid residue 421 (glycine -> serine) of the enzyme. Dot and Northern analyses showed that the gua1 gene was expressed in transformants as well as in the wild-type and the gua1ura4-D18 mutant, but enzyme activity was only detected in wild-type and transformant cells. It seems likely that a 446 bp fragment from the 3' end of the gua1 gene abolished the point mutation in the mutant strain, suggesting that this fragment participates in the sequences encoding the active domain of IMPDH in S. pombe