Conserving Plants in Gene Banks and Nature: Investigating Complementarity with Trifolium thompsonii Morton

Abstract

A standard conservation strategy for plant genetic resources integrates in situ (on-farm or wild) and ex situ (gene or field bank) approaches. Gene bank managers collect ex situ accessions that represent a comprehensive snap shot of the genetic diversity of in situ populations at a given time and place. Although simple in theory, achieving complementary in situ and ex situ holdings is challenging. Using Trifolium thompsonii as a model insect-pollinated herbaceous perennial species, we used AFLP markers to compare genetic diversity and structure of ex situ accessions collected at two time periods (1995, 2004) from four locations, with their corresponding in situ populations sampled in 2009. Our goal was to assess the complementarity of the two approaches. We examined how gene flow, selection and genetic drift contributed to population change. Across locations, we found no difference in diversity between ex situ and in situ samples. One population showed a decline in genetic diversity over the 15 years studied. Population genetic differentiation among the four locations was significant, but weak. Association tests suggested infrequent, long distance gene flow. Selection and drift occurred, but differences due to spatial effects were three times as strong as differences attributed to temporal effects, and suggested recollection efforts could occur at intervals greater than fifteen years. An effective collecting strategy for insect pollinated herbaceous perennial species was to sample >150 plants, equalize maternal contribution, and sample along random transects with sufficient space between plants to minimize intrafamilial sampling. Quantifying genetic change between ex situ and in situ accessions allows genetic resource managers to validate ex situ collecting and maintenance protocols, develop appropriate recollection intervals, and provide an early detection mechanism for identifying problematic conditions that can be addressed to prevent further decline in vulnerable in situ populations.

Genetic Diversity and Population Structure of Toona Ciliata Roem. Based on Sequence-Related Amplified Polymorphism (SRAP) Markers

“…The conservation generally includes in situ (on-farm or wild) and ex situ (gene or field bank) approaches. The achieving complementary in situ and ex situ holdings is great important for perennial species [42]. As for the broad-leaf species, which has a longer life history, extant natural forests of T. ciliata exist in the form of ancient trees.…”

Genetic Distinctiveness of Rye In situ Accessions from Portugal Unveils a New Hotspot of Unexplored Genetic Resources

“…Landrace can be defined following (Camacho-Villa et al, 2005), as: “a dynamic population of a cultivated plant that has historic origin, distinct identity and lacks formal crop improvement, as well as often being genetically diverse, locally adapted and associated with traditional farming systems.” Furthermore, landraces can be separated in ex situ and in situ collections: the former being those detained in gene banks or botanical gardens which represent a comprehensive snapshot of the genetic diversity at a given time and place (Greene et al, 2014); while in situ allows adaptive evolutionary processes to continue shaping genetic diversity under farmer management. In plant genetic resources (PGR) conservation, it has long been recognized that effective strategies need to integrate in situ and ex situ approaches (Greene et al, 2014). Studies reported the complementary source of genetic variation between in situ and ex situ collections, as some of the alleles may have been lost in situ (e.g., Jensen et al, 2012) or ex situ (e.g., Li et al, 2005).…”

Genomic Prediction Within and Among Doubled-Haploid Libraries from Maize Landraces

“…First, one must identify the most promising accessions, commonly based on passport data provided by seed banks and results from field trials, in which the landraces are evaluated for their per se performance and/or testcross performance with suitable testers (Salhuana and Pollak 2006;Böhm et al 2014). Selection among accessions is not sufficient because both molecular and phenotypic data from various crops suggest that more genetic variation lies within than between landraces (Greene et al 2014;Monteiro et al 2016;Böhm et al 2017;Mayer et al 2017). Therefore, the second challenge is mining the genetic diversity within landraces, preferably in the form of inbred lines.…”