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A study of wild tomatoes endemic to the Galapagos Islands as a source for salinity tolerance traitsPailles, Yveline 11 1900 (has links)
Salinity is a major concern in agriculture since it adversely affects plant growth,
development, and yield. Domestication of crops exerted strong selective pressure and
reduced their genetic diversity. Meanwhile, wild species continued to adapt to their
environment becoming valuable sources of genetic variation, with the potential for
enhancing modern crops performance in today’s changing climate. Some wild species are
found in highly saline environments; remarkable examples are the endemic wild
tomatoes from the Galapagos Islands, forming the Solanum cheesmaniae and Solanum
galapagense species (hereafter termed Galapagos tomatoes). These wild tomatoes
adapted to thrive in the coastal regions of the Galapagos Islands.
The present work includes a thorough characterization of a collection of 67 accessions of
Galapagos tomatoes obtained from the Tomato Genetics Resource Center (TGRC).
Genotyping-by-sequencing (GBS) was performed to establish the population structure
and genetic distance within the germplasm collection. Both species were genetically
differentiated, and a substructure was found in S. cheesmaniae dividing the accessions in
two groups based on their origin: eastern and western islands. Phenotypic studies were performed at the seedling stage, subjecting seedlings to 200 mM
NaCl for 10 days. Various traits were recorded and analysed for their contribution to
salinity tolerance, compared to control conditions. Large natural variation was found
across the collection in terms of salt stress responses and different possible salt tolerant
mechanisms were identified. Six accessions were selected for further work, based on their
good performance under salinity. This experiment included scoring several plant growth
and yield-related traits, as well as RNA sequencing (RNAseq) at the fruit-ripening stage,
under three different NaCl concentrations. Accession LA0421 showed an increased yield
of almost 50% in mild salinity (150 mM NaCl) compared to control conditions. The
transcriptome data obtained could reveal the genes involved in the salt stress-related
yield increase. The knowledge obtained so far will be useful for scientists and breeders to select
accessions of interest based on recorded traits. It will allow the use of Galapagos
tomatoes as genetic sources for salinity tolerance traits in commercial tomatoes, thereby
contributing to feed and nourish the growing human population in the years to come.
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Comparative Genomics of Gossypium spp. through GBS and Candidate Genes – Delving into the Controlling Factors behind Photoperiodic FloweringYoung, Carla Jo Logan 16 December 2013 (has links)
Cotton has been a world-wide economic staple in textiles and oil production. There has been a concerted effort for cotton improvement to increase yield and quality to compete with non-natural man-made fibers. Unfortunately, cultivated cotton has limited genetic diversity; therefore finding new marketable traits within cultivated cotton has reached a plateau. To alleviate this problem, traditional breeding programs have been attempting to incorporate practical traits from wild relatives into cultivated lines. This incorporation has presented a new problem: uncultivated cotton hampered by photoperiodism.
Traditionally, due to differing floral times, wild and cultivated cotton species were unable to be bred together in many commercial production areas world-wide. This worldwide breeding problem has inhibited new trait incorporation. Before favorable traits from undomesticated cotton could be integrated into cultivated elite lines using marker-assisted selection breeding, the markers associated with photoperiod independence needed to be discovered. In order to increase information about this debilitating trait, we set out to identify informative markers associated with photoperiodism.
This study was segmented into four areas. First, we reviewed the history of cotton to highlight current problems in production. Next, we explored cotton’s floral development through a study of floral transition candidate genes. The third area was an in-depth analysis of Phytochrome C (previously linked to photoperiod independence in other crops). In the final area of study, we used Genotype-By-Sequencing (GBS), in a segregating population, was used to determine photoperiod independence associated with single nucleotide polymorphisms (SNPs).
In short, this research reported SNP differences in thirty-eight candidate gene homologs within the flowering time network, including photoreceptors, light dependent transcripts, circadian clock regulators, and floral integrators. Also, our research linked other discrete SNP differences, in addition to those contained within candidate genes, to photoperiodicity within cotton. In conclusion, the SNP markers that our study found may be used in future marker assisted selection (MAS) breeding schemas to incorporate desirable traits into elite lines without the introgression of photoperiod sensitivity.
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