CELLULAR AND MOLECULAR APPROACHES TO THE BREEDING BARRIER IN PLANTS, APOMIXIS.

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Cytological Approach: At first, the evaluation of the apomictic ratio was performed in facultative apomict species, Guineagrass and Bahiagrass by means of Nomarski's differential interference contrast mirography (DIC). Then, virietal differences of the capability to form adventitious embyos in tissue culture were compared with that of apomictic ratios. There was some corelations among them. In situ hybridization experiment was also carried out at mRNA levels in each developmental stages of zygotic embryo by using DNA probes concerning to the adventitious embryo formation in alfalfa and rice. To now, unfortunately, technical problems still remain to be resolved.Molecular Approach: By checking the stage at which apospory is determined in Guineagrass, some candidate of cDNA were isolated from developmentally selected samples by means of simplified Differential Display Methods (DD). The gene expression of the candidates were confirmed by Northern hybridization. And then, homology search of candidate, A2-134 was performed with the BLAST-Version 2.1 PIR database. Database search for sequence homology unvailed a relation to the RD22 gen of Arabidopsis thaliana with 50.9% similarity in nucleotide sequence. The RD22 protein regulates the expression of seed-specific genes and probably also genes in responcse to dehydration stress.