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Phenotypic diversity of USDA guayule germplasm collection grown under different irrigation conditions

Zinan Luo, Hussein Abdel-Haleem
Industrial crops and products 2019 v.142 pp. 111867
Parthenium argentatum, USDA, agronomic traits, deserts, environmental impact, genetic improvement, genetic variation, genotype-environment interaction, germplasm conservation, guayule, heritability, industrial byproducts, industry, irrigation, latex, phenotype, phenotypic variation, phytomass, ploidy, resins, rubber, water stress, Mexico, Texas
Parthenium argentatum (guayule), originated from northern Mexico and southern Texas deserts, is a good candidate for arid and semi-arid sustainable agricultural systems to produce domestic natural rubber and other industrial byproducts. Exploring the genetic and phenotypic diversities of guayule germplasm collections is required for continuous genetic improvement of guayule characteristics to meet the growing demand of guayule for rubber, resin and latex industries. The current study phenotypically evaluated a larger guayule USDA germplasm collection than before, with 56 accessions for 10 important morphological and agronomic traits evaluated, which include plant biomass, rubber and resin content, rubber and resin yield. The accessions were grown under two different irrigation conditions: well-watered and water-stressed environments. Significant genotypic effects were found for all studied traits indicating the wide genetic variability of this collection. Significant Environmental effects were found in rubber content, resin content, rubber yield and dry weight biomass. No significant genotype-by-environment interactions (GEI) were observed indicating the similarity of those accessions across growing conditions. Moderate to high entry-mean heritability values were estimated for these traits, suggesting that selection is feasible to enhance the genetic gain. Significant inter-trait correlations were found between biomass-related traits and resin/rubber yield, as well as ploidy levels and resin/rubber content, indicating the possibility of improving multiple traits at one time. To conclude, this study explored the phenotypic variations of the USDA guayule germplasm under different irrigation conditions, which will provide recommendations for parent and off-spring selections to enhance the breeding values in guayule breeding programs.