Adoption of conservation farming practices such as zero tillage when planting field research plots is essential to the replication of on-farm practices. The problem is that most drill options fail to meet expectations as they are not built to the scale required, compromise the need for uniformity of plant emergence within plot areas, lack portability, or have been designed and equipped in a manner that is not relevant to farm-scale seeder technologies and practices. Agronomists and Technicians at Agriculture and Agri-Food Canada engaged with engineering expertise to design and build two prototype drills that are now in full operation.
Results of nine replicated provenance trials of silver birch (Betula pendula Roth) growing in Great Britain and Ireland are described. Five of the trials compare provenances from Scotland and the north of England measured after 10 or 11 years of growth; the remaining four trials compare provenances from across Great Britain, Ireland and the near-continent measured after 8 years of growth. In total, 64 provenances were tested. Survival was generally high across all sites with a mean of 79 per cent for the first five trials, and 89 per cent for the remaining four. The study found significant differences in mean height growth between trial sites and between provenances within each trial site. Although there was statistically significant site by provenance interaction, the better and poorer provenances were consistent across the range of sites tested. Mean height growth of the provenances under test was inversely correlated with latitude of origins, southern origins generally performing better. There was some evidence that further variation can be explained by incorporating details of longitude, accumulated temperature and potential moisture deficit for the origin. Elevation had little impact on explaining provenance performance. There was no evidence for the superior performance of provenances originating close to the trial site, other than for the southern-most trials. The relatively poor height growth of provenances from upland Scotland at even local trial sites suggests excessively conservative adaptation. The data suggest northern movement of provenances by at least 2 degrees latitude or 200 km would bring the benefits of improved height growth and yet carry little risk of poorer survival under current climate conditions and could perhaps be extended further according to predictions of future climate warming.
Phytophthora cinnamomi is the causal agent of root rot, canker, and dieback of thousands of plant species around the globe. This oomycete not only causes severe economic losses to forestry and agricultural industries, but also threatens the health of various plants in natural ecosystems. In this study, 380 isolates of P. cinnamomi from four avocado production areas and two regions of natural vegetation in South Africa were investigated using 15 microsatellite markers. These populations were found to have a low level of genetic diversity and consisted of isolates from three lineages. Shared genotypes were detected between isolates from avocado orchards and natural vegetation, indicating the movement of isolates between these areas. The population from the Western Cape natural vegetation had the highest level of genotypic diversity and number of unique alleles, indicating this could be the point of introduction of P. cinnamomi to South Africa. Index of association analysis suggested that five of six populations were under linkage disequilibrium, suggesting a clonal mode of reproduction, whereas genotypes sampled from a recently established avocado orchard in the Western Cape were derived from a randomly recombining population. This study provided novel insights on the genetic diversity and spread of P. cinnamomi in South Africa. It also reported on the predominance of triploidy in natural occurring populations and provided evidence for recombination of P. cinnamomi for the first time. The presence of two dominant genotypes in all avocado production areas in South Africa highlight the importance of considering them in disease management and resistance breeding programs.
Current forestry policy promotes the use of local seed for new plantings, on the assumption that local material may be better adapted to local conditions. However, landscape-scale genetic studies which are necessary to underpin conservation and breeding strategies are often lacking. We investigated molecular diversity in common ash (Fraxinus excelsior L.) sampled from 42 British and six French sites with microsatellites. Chloroplast haplotype H04 was the most common and widespread in Britain, although rare and localized individuals with H02 and H09 were also detected. In addition, three new chloroplast haplotypes were identified, and these were rare and highly localized. In terms of nuclear microsatellite markers, allelic richness differed between sites and decreased in an east to west direction. Differentiation between sites was often very low (mean F(ST) 0.025), indicating few differences between the majority of sites. There was a clear excess of homozygotes (mean H(O) 0.669, mean H(E) 0.818) and a relatively high F(IS) (mean 0.182), suggests a consistent level of inbreeding or a widespread Wahlund effect in many F. excelsior sites. Gene pool ancestry analysis suggested that the majority of British F. excelsior belongs to a single meta-population which covers mainland western and central Europe. Three northern and western sites diverged markedly from the dominant population, and may represent remnants of two late potential Ice Age refugia in northern Britain. The data provide new information which will aid development of appropriate conservation policies for ash and other wind pollinated tree species.
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