Diversity is well known in natural systems to buffer plant populations from environmental stressors, herbivores, pathogens and to promote persistence. Less well-studied is whether genetic diversity within crops also provides a similar buffering effect. Genetic diversity is assumed to directly result in trait variation, although selection for agricultural yield may reduce much of this variation.
This study addressed whether genetically diverse varieties of hazelnut (Corylus) also possess greater trait variation than genetically uniform varieties. Trait variation was examined across three experimental orchards containing replicated plantings of two clonally produced (no diversity) and two seedling lines (diverse) of hazelnut. Four fundamental leaf traits were examined across this system: specific leaf area (SLA), leaf dry matter content (LDMC), leaf area (LA), and chlorophyll content (CC). Measurements were taken from four replicate leaves per plant. Variance partitioning was used to evaluate the contribution of site, variety and individual to trait variation across seedling and clonal lines. This analysis was followed by a multivariate dispersion test to analyze overall trait variation across varieties.
Results/Conclusions
Contrary to expectations, seedlings and clones showed similar overall levels of variation for all traits. However, the sources of variation were different between seedlings and clones. Variance partitioning revealed that seedling lines had greater variation across individuals for all traits except CC. In contrast, clones generally had lower variation across individuals, with greater variation contributed by site. Cumulatively, these results indicate that there are subtle differences in how genetic diversity impacts trait variation. The multivariate dispersion test showed that among varieties, clonal lines had both the highest and lowest levels of trait variation, with seedling lines having intermediate levels of variation. Our results show that patterns in trait variation do not cleanly follow the expectations based on natural systems. As traits should be related to variation in performance, understanding the contribution of genetic diversity to trait variation is important for agroecosystems.