Exploring Relationships Among Above and Belowground Phenotypic Traits
Exploring Relationships Among Above- and Belowground Phenotypic Traits in Guar (Cyamopsis tetragonoloba L. ) Ø Introduction o Guar is low input legume adapted to semi-arid environments with excellent heat, drought, and salt tolerance. o Primary use of guar is galactomannan gum derived from its seed endosperm. o In addition to a marketable seed product, a primary motivation for producing guar is the anticipated soil-N (Nitrogen) credits from biological N-fixation. o U. S. guar production is limited and unstable. o The last major guar variety releases in the U. S. occurred around 1985, and several oil and gas-specific releases in ~2005. o Improvement of U. S. guar germplasm depends on better understanding of both plant productivity and N-fixation traits. Ø Objective o To characterize phenotypic variation within measured plant parameters and establish pertinent relationships among above- and belowground traits.
Materials & Methods Ø Experimental Design and information o Pot study using sandy loam soil – Controlled conditions at Vernon, TX. o Completely randomized design (CRD) – 4 replications. o Treatments – 50 guar genotypes. o Irrigation was managed at 100% ET replacement using a gravimetric technique. o Harvest – ~50 days after planting (DAP). Ø Data collection o Aboveground morpho-physiological traits (12). o Belowground root nodulation traits (2). Ø Data analysis o Using SAS 9. 4 software & R-studio. o Biometric parameters – PROC MEANS. o Correlation analysis – PROC CORR. o Biplot analysis using Principal component analysis (PCA) – Agricolae package.
Ø Results & Discussion o Plant N-content was correlated to nodule weight and biomass/biomass components indicating high N-fixation and N-accumulation in genotypes with a greater biomass and nodule productivity. o Interestingly, both the nodule number and weight were positively related to stem diameter, which suggests a relationship between stem and root system sizes, including the ability to support nodulation. o Number of branches was positively related to biomass production parameters, excluding reproductive biomass, but this relationship is likely reflecting varietal differences in maturity (reproductive development) due to short growing period. o Specific leaf area (SLA) varied by > 49 cm 2/g leaf mass. This variation may be exploited by plant breeders to optimize potential SLA tradeoffs in leaf area production efficiency (relating to photosynthetic light interception) and leaf thickness (relating to drought tolerance trait). Ø Conclusion o A substantial phenotypic and genotypic variation exists for guar germplasm improvement in relation to drought tolerance, N-fixation, and plant productivity traits. Thank You !
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