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These results suggest that the presence of restraint stress significantly enhances the progression of P. gingivalis-challenged periodontitis in rats.

Four Japanese wheat varieties, three crossable and one non-crossable with Hordeum bulbosum, were pollinated with maize pollen of 5 genotypes. By the application of 2,4-dichlorophenoxyacetic acid after pollination, embryos kept developing on wheat plants until 14 days after pollination. The frequency of embryo formation was significantly different among the maize genotypes, varying from 18.0% to 31.9%, but not among the wheat varieties. By bagging spikes with flag leaves the frequency of embryo formation was increased by about 7%. Ten- to twelve-day-old embryos gave higher frequencies of plant formation (83.6%) than 14-day-old embryos(50.0%). All 6 regenerated plants investigated cytologically were found to be haploid. Twelve of the 14 colchicine-treated plants produced florets setting seeds. The overall efficiency of our procedure is considered to be higher than that reported by Laurie and Bennett (1988).

SynopsisA genetic linkage map of guinea grass ( Panicum maximum Jacq.) was generated with nine of the AFLP markers found to be associated with apospory. These aposporyassociated markers were assigned to a linkage group having previous association with microsporogenesis of the aposporous guineagrass cultivar 'Natsukaze'. An aposporous linkage group was constructed utilizing 38 AFLP markers. Embryo sac analysis revealed that sexual and apomictic embryo sacs occurred at a frequency of 1 : 1, indicating simple inheritance of a single major gene controlling apospory in guineagrass. In addition, utilizing 56 AFLP primer combinations and 41 RAPD primers, 39 linkage groups and 360 simplex marker loci were assigned to the genetic map of the 'Natsukaze' cultivar. These markers covered 1703.5 cM of the autotetraploid guineagrass genome (2n = 4x = 32), with an average spacing of 4.7 cM. These tightly linked markers to apospory locus in guineagrass could be a powerful tool for marker-assisted selection of apospory and map-based cloning of the apospory gene.

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