ABSTRACT
A cDNA sequence (Hbc8-2) isolated from pistils of the self-incompatible species Hordeum bulbosum was analysed for expression pattern and genetic map location. Hbc8-2 was expressed just prior to anthesis in mature pistils, and expression was maintained at a high level throughout anthesis. The same expression pattern was found in self-incompatible rye ( Secale cereale), but no expression was detected in the self-compatible cereals wheat ( Triticum aestivum) or barley ( Hordeum vulgare) at comparable stages of development. However, three wheat expressed sequence tags from a pre-anthesis library had high homology to Hbc8-2. Southern blot analyses using Hbc8-2 as a probe detected hybridising bands in the genomes of various Gramineae species including rye, barley, bread wheat, wild wheat relatives ( Aegilops tauschii and Ae. speltoides), oats ( Avena fatua and A. strigosa), rice ( Oryza sativa) and maize ( Zea mays). This suggests that Hbc8-2-like sequences are present in many species but that high levels of expression may be associated with self-incompatibility. Hbc8-2 was mapped on the long arms of chromosome 2H(b) of H. bulbosum, 2R of rye, and 2B and 2D of wheat and was assigned to chromosome 2H of barley using wheat/barley addition lines. On a H. bulbosum genetic map, Xhbc8-2 was located between Xbcd266 and Xpsr87, while in rye and wheat it was located in a 13.2-cM interval between Xpsr331 and Xpsr932, consistent with previous comparative mapping studies of these species. Mapping in rye suggested that Hbc8-2 is probably proximal to the Z self-incompatibility locus which was previously shown to be tightly linked to Xbcd266.
ABSTRACT
The objectives of this study were (1) to investigate the genetic variability; and (2) to determine the phylogenetic relationship in the leguminous tree Faidherbia albida through out its range of distribution in East, West and Southern Africa. A total of 16 populations were subjected to enzyme electrophoresis and 6 enzyme systems (Adh, Mdh, G6pdh, Idh, 6Pgdh, and alpha-Est) encoded by 12 loci were scored. A total of fifty one different alleles were detected, with an average of 2.5 alleles per locus. Forty three percent of the loci were polymorphic at a 95% criterion. The average expected heterozygosity (gene diversity index H(e)) was 0.141. All provenances showed significant deviation from Hardy-Weinberg expectation. The UPGMA cluster analysis, based on Modified Rogers distance revealed close similarities between Eastern and Southern African provenances, except Debre zeit from Ethiopia, which was closest to West African populations than to the East African populations. Also, Bignona from West Africa was peculiarly closer to East African provenances. Differentiation of West African populations from Eastern and Southern African provenances was quite evident, emphasising the clinical pattern of variation in these two major geographical races of F. albida in Africa. Wright's F-statistics showed an overall significant deficit of heterozygotes, a common feature in mixed mating, entomophilous, widespread species such as F. albida. The dendrogram analysis showed wide separation among the three Ethiopian provenances indicating a high level of genetic differentiation and diversity among them.
