The“genetic erosion”of the soil ecosystem

This paper takes into consideration the influence of human activities on the loss of pedodiversity in a Mediterranean area due to large scale farming.In particular it examines the quantitative and qualitative soil changes in a period of 53 years(from 1955 to 2008)evaluating the loss of soil diversity at soil subgroups level of the USDA Soil Taxonomy system.The following indices were used:richness;Shannon’s diversity index;Simpson diversity index;Shannon’s evenness index;Simpson’s evenness index.In this case study,considering what we observed in time,the human intervention in soil transformation could increase the diversity in the landscape in an initial phase,but forwarding by large scale farming the result is a huge loss of pedodiversity in time,as diversity indices remarkably have shown.This analysis enabled identification of disappeared soil types,with their unique history of formation.In our opinion this strongly reflects a sort of“genetic erosion”of the soil types,resulting in a substantial weakening of the whole pedo-ecosystem.

A Discussion on Possible Indicators Related to Genetic Structure Changes in Plant Germplasm Conservation

The purpose of the present paper is to study and develop indicators and procedures for the evaluation of genetic structure changes in germplasm conservation due to social and natural environment reasons. Some basic concepts in germplasm study were introduced at first. Then, six kinds of indicators for genetic diversity as a measure of genetic potential of a germplasm collection were presented, i.e., numbers of different entities at certain level, evenness of the entity distribution, genetic similarity and genetic distance, genetic variance and genetic coefficient of variation, multivariate genetic variation indices, and coefficient of parentage. It was pointed out that genetic dispersion did not provide a complete concept of genetic diversity if without any information from genetic richness. Based on the above, the indicators for genetic erosion as the genetic structure changes of germplasm conservation due to social reasons, the indicators of genetic vulnerability as the genetic structure changes of germplasm conservation due to environmental stresses, the measurement of genetic drift and genetic shift as the genetic structure changes of germplasm collection during reproduction or seed increase were reviewed and developed. Furthermore, the estimation procedures of the indicators by using molecular markers were suggested. Finally, the case studies on suitable conservation sample size of self-pollinated and open-pollinated populations were given for reference.

Historical and Traditional Notes on Collecting Crop Genetic Resources in Central Part of Calabria Region

A collecting expedition has been carried out in the central part of Calabria region, south Italy; it has been concentrated on Reventino, Serre, Occitan and Albanian areas that were covered in certain coinciding sites in the past. In totality, 50 accessions belonging to 14 taxa were collected from 8 collecting sites, representing mainly highly variable old landraces of vegetables and cereals and, especially, of pulses; most of them that appear severely threatened by genetic erosion are still cultivated, at certain level, by old farmers and directly used by their families. A comparison of the results of the previous missions that have been carried out in Calabria region that preserve valuable crop genetic resources on farm shows the large degree of genetic erosion for all crops collected. The results stressed the need to conserve a considerable amount of material endangered and the necessity of our ongoing care for their preservation either on farms or ex situ in genebanks. The complementarity of both conservation methods is needed.

Effects of Logging on the Genetic Diversity of Quercus tiaoloshanica Chun et Ko in a Tropical Montane Forest of Hainan Island, Southern China

Quercus tiaoloshanica Chun et Ko, which has a narrow range of distribution, is one of the important endemic species of the tropical montane rain forest on Hainan Island, southern China. Long-term logging and habitat destruction have resulted in population decline and distribution retreat of Q. tiaoloshanica. To determine the impact of logging on the genetic diversity of Q. tiaoloshanica, the authors investigated the genetic structures using amplified fragment length polymorphism markers in four regenerated stands after logging and in one unlogged stand. Compared with the unlogged stand, the effective number of alleles per locus dropped by 1.0% in selective logging stands and by 2.0% in clear logging stands, corresponding to reductions of 3.8% and 5.2%, respectively, in mean Nei＇s gene diversity and 2.9% and 3.5%, respectively, in mean Shannon diversity index. No substantial genetic erosion was detected in any of the regenerated stands owing to the high tree density and high heterogeneity of the Q. tiaoloshanica stands investigated. Meanwhile, there was no natural regeneration of the species observed in a Dacrydium pierrei Hickel plantation 700 m away from the regenerated stands, suggesting the limited ability of seed dispersal of Q. tiaoloshanica. Clear logging should be undertaken cautiously because the total number of plant species dropped by 15.2% in the clear-logged stands compared with the unlogged stand. To conserve the genetic diversity of this species, as well as the plant biodiversity of tropical forests, the habitats of Q. tiaoloshanica should be protected against exploitation in terms of agricultural or other forms of land use, and some mature trees should be preserved as seed sources to maintain an adequate regeneration base for this species in the management of logging.