Comparative genetic maps of Papuan Saccharum officinarum L. (2n ‫؍‬ 80) and S. robustum (2n ‫؍‬ 80) were constructed by using single-dose DNA markers (SDMs). SDM-framework maps of S. officinarum and S. robustum were compared with genetic maps of sorghum and maize by way of anchor restriction fragment length polymorphism probes. The resulting comparisons showed striking colinearity between the sorghum and Saccharum genomes. There were no differences in marker order between S. officinarum and sorghum. Furthermore, there were no alterations in SDM order between S. officinarum and S. robustum. The S. officinarum and S. robustum maps also were compared with the map of the polysomic octoploid S. spontaneum 'SES 208' (2n ‫؍‬ 64, x ‫؍‬ 8), thus permitting relations to homology groups (''chromosomes'') of S. spontaneum to be studied. Investigation of transmission genetics in S. officinarum and S. robustum confirmed preliminary results that showed incomplete polysomy in these species. Because of incomplete polysomy, multipledose markers could not be mapped for lack of a genetic model for their segregation. To coalesce S. officinarum and S. robustum linkage groups into homology groups (composed of homologous pairing partners), they were compared with sorghum (2n ‫؍‬ 20), which functioned as a synthetic diploid. Groupings suggested by comparative mapping were found to be highly concordant with groupings based on highly polymorphic restriction fragment length polymorphism probes detecting multiple SDMs. The resulting comparative maps serve as bridges to allow information from one Andropogoneae to be used by another, for breeding, ecology, evolution, and molecular biology.

The extent of natural variation among wild type Arabidopsis thaliana L. Heynh for response to environmental stimuli that affect flowering is poorly documented. The effects of photoperiod and vernalization on the number of rosette leaves at the time of anthesis was measured for 32 Arabidopsis ecotypes. All ecotypes were vernalized 24 days at 4 C under continuous illumination. Vernalized and non vernalized plants were transplanted into 8-(short-day) and 20-hour (long-day) photoperiods In controlled environment growth chambers. Two ecotypes failed to flower after 110 days. Mean leaf number was less for all ecotypes under long day compared to short day. Sixteen ecotypes responded to vernalization; eight had reduced leaf number regardless of photoperiod, and eight had reduced leaf number only under short day. Two ecotypes required vernalization to flower in this study. For three ecotypes, vernalization and short day resulted in a reduction in leaf number whereas vernalization and long day resulted in increased leaf number. Documentation of the effects and interactions of photoperiod and vernalization across many ecotypes provides a broader range of described natural variation for genetic and physiologic study.

Genetic diversity within the azuki Vigna angularis (Willd.) Ohwi and Ohashi genepool has not been extensively examined with molecular markers. The objectives of this study were to: (i) use RAPD and AFLP analyses to assess the genetic similarity among selected azuki accessions from distinct production regions in Asia, and( ii) compare the utility of the two DNA marker systems for evaluating similarity. Results also will provide information for parental selection in a breeding program. Fifty‐seven RAPD and 214 AFLP bands were used to assess genetic diversity among 58 azukia acessions. Thirty percent of the RAPD and 18% of the AFLP amplification products were polymorphic among accessions. One AFLP primer pair detected a mean of 11.3 polymorphic bands per reaction versus a mean of 3.2 for each RAPD primer. On the basis of Jaccard's similarity coefficients (JSCs), higher level of molecular genetic variation was detected among accessions evaluated in this study than in other diversity assessments of azuki. Mean JSC based on AFLP data was significantly higher than that obtained from RAPD data (0.71 and 0.52, respectively), and results from phylogenetic analyses varied between DNA marker systems. A substantial difference in the number of polymorphic bands detected through AFLP versus RAPD analysis may have influenced these results since the ability to resolve genetic relationships among genotypes is related to the number of polymorphisms detected. Cluster analysis revealed groupings among accessions; however, no apparent correlations with putative geographic origin were detected. Results of this study suggest that the level of genetic diversity among selected azuki accessions should be sufficient for developing an intraspecific mapping population.

The extent of natural variation among wild type Arabidopsis thaliana L. Heynh for response to environmental stimuli that affect flowering is poorly documented. The effects of photoperiod and vernalization on the number of rosette leaves at the time of anthesis was measured for 32 Arabidopsis ecotypes. All ecotypes were vernalized 24 days at 4 C under continuous illumination. Vernalized and nonvernalized plants were transplanted into 8‐ (short‐day) and 20‐hour (long‐day) photoperiods in controlled environment growth chambers. Two ecotypes failed to flower after 110 days. Mean leaf number was less for all ecotypes under long day compared to short day. Sixteen ecotypes responded to vernalization; eight had reduced leaf number regardless of photoperiod, and eight had reduced leaf number only under short day. Two ecotypes required vernalization to flower in this study. For three ecotypes, vernalization and short day resulted in a reduction in leaf number whereas vernalization and long day resulted in increased leaf number. Documentation of the effects and interactions of photoperiod and vernalization across many ecotypes provides a broader range of described natural variation for genetic and physiologic study.

No abstract