Accessing Stress Physiological and Morphological Diversity in the Tetraploid Cultivated Cotton Germplasm through the Gossypium Diversity Reference Set

The Gossypium Diversity Reference Set (GDRS), a subset from the National Cotton Germplasm Collection, captures the total spectrum of geographical and morphological diversity within diploid and tetraploid Gossypium species collected worldwide, as well as within land races and obsolete cultivars of the commercial tetraploid species, G. hirsutum and G. barbadense. Our goal is to mine a representative sample based on previous analysis of 105 polymorphic SSR loci distributed across the G. hirsutum genome for various physio-morphometric traits that contribute to quantitative variation for abiotic stress tolerance mechanisms. Subsequently, we aim to create reference physiological, transcriptomic, genomic, and epigenomic resources for representative genotypes that could serve as donors for each morpho-physiometric trait in genomics-assisted cotton breeding programs.

Here we present the initial set of data showing the spectrum of stress physiological variation across this smaller diversity panel (50 accessions). Accessing the range of potential stress tolerance or avoidance mechanisms associated with morphological and developmental traits, we have begun to conduct preliminary morpho-developmental comparisons with half the diversity panel grown under greenhouse condition. We measured 27 morphological characters intended to capture habit, reproductive, developmental, and phenotypic variation. Trends revealed by regression and multivariate analyses indicate that morphological diversity in a small sample of the GDRS is inconsistent with diversity predicted from SSR data. We are further examining the lack of congruence between the morpho-developmental and SSR data in order to discover some unique attributes with potential significance to stress tolerance and/or avoidance mechanisms not predicted by variation on repetitive DNA sequences.