Inbreeding effects in Solanum lycocarpum A. St.-Hil populations, an endangered species of the Brazilian Cerrado.

The inbreeding effective population size is an estimate of inbreeding and genetic drift in populations. It is an important tool for conservation genetics because it represents the number of individuals that are effectively contributing alleles to the subsequent generations. Several studies have been published in the last decades on the genetic structure of natural plant populations of the Cerrado, the Central-Brazilian savannahs, but most of them do not present effective size estimates. The objective of this study was to show such estimates for Solanum lycocarpum, a Cerrado species that is in danger of genetic erosion. We utilized microsatellites, isozymes, and 2 natural populations for each marker to estimate the population inbreeding effective size of a group of populations (N(^)e(v)) and the minimum number of populations that should be conserved (S(^)(ref)) in order to retain an effective number of 500. For the 2 markers that were utilized, only approximately 12% of the individuals are effective in the populations. The value obtained for S(^)(ref) was approximately 80.

Simple-sequence repeat markers of Cattleya coccinea (Orchidaceae), an endangered species of the Brazilian Atlantic Forest.

Microsatellite markers were developed for the endangered Brazilian orchid species Cattleya coccinea to describe its genetic diversity and structure and to support conservation studies. Nine microsatellite loci were isolated and characterized using an enriched genomic library. All loci are polymorphic at least in the 2 populations sampled, except for loci Cac05 and Cac09 for the Petrópolis population. The mean number of alleles per locus was 8.8 between populations. The mean values of the observed and expected heterozygosities were 0.541 (ranging from 0 to 1) and 0.639 (ranging from 0 to 0.9), respectively. Cross-amplifications were performed in 7 additional Epidendroideae species, and at least 2 loci were successful in 3 additional Cattleya species, Epidendrum secundum, and Brasiliorchis gracilis. All markers described herein will be useful in further studies evaluating the genetic diversity, population dynamics, and conservation genetics of C. coccinea and related species.

Variation in the loss of seed dormancy during after-ripening of wild and cultivated rice species.

BACKGROUND AND AIMS: The aim of this paper was to verify the variation in the loss of seed dormancy during after-ripening and the interspecific and interpopulation variability in the degree of dormancy of seven wild and two cultivated rice species comprising 21 populations and two cultivars. METHODS: Four wild rice species from South America, Oryza glumaepatula, O. latifolia, O. grandiglumis and O. alta, and two O. sativa cultivars were tested in one experiment. In a second experiment, five wild species, O. punctata, O. eichingeri, O.rufipogon, O. latifolia and O. glumaepatula, and one cultivated species (O. glaberrima) were evaluated. Initial germination tests were performed soon after the seeds were harvested and subsequently at 2-month intervals, for a total of six storage periods in the first experiment and three in the second. All tests were conducted in the dark at a temperature of 27 degrees C. KEY RESULTS: Different patterns of after-ripening among populations within and between species were observed. CONCLUSIONS: The cultivated species (O. sativa and O. glaberrima) and, amongst the wild species, the tetraploids O. latifolia, O. grandiglumis and the diploids O. eichingeri and O. punctata, had weak dormancy, losing it completely 2 months after harvest, while O. rufipogon and O. glumaepatula exhibited pronounced dormancy. The latter showed different patterns of after-ripening between populations indigenous to the Amazon region and those originating in the Paraguay River system. Seeds of Solimoes (Amazon) and Japura origin showed weak dormancy whereas those of Paraguay origin showed deep dormancy. Ecological differences among natural habitats may be involved in such differentiation.