Upper and Lower Heritability Estimates in Guayule Based on Mode of Reproduction

Abstract

<jats:p>Guayule (<jats:italic>Parthenium argentatum</jats:italic> Gray) has been difficult to improve through classical plant breeding because of its facultative apomictic reproductive system and long growth period to harvest (2–5 years). Attempts have been made to increase rubber concentration and yield by selecting for traits correlated with rubber production. The objective of this study was to estimate heritability values in guayule that more accurately account for the contributions of apomictic and sexual reproduction occurring among populations, using a modified parent–progeny regression. Heritability was calculated using a modified version of the formula for single parent–progeny regression (<jats:italic>h</jats:italic> <jats:sup>2</jats:sup> = 2<jats:italic>b</jats:italic>): that is, <jats:italic>h</jats:italic> <jats:sup>2</jats:sup> = (2 – <jats:italic>p</jats:italic>)<jats:italic>b</jats:italic>, where <jats:italic>p</jats:italic> = proportion of apomixis and <jats:italic>b</jats:italic> = regression coefficient. Therefore, heritability was estimated as a range of values between the midparent and single parent regression, which correspond to complete apomixis and complete sexuality, respectively. At 2 years of growth, there was a significant regression between each parent trait and the corresponding progeny trait except rubber and guayulin B concentrations, with heritability estimates ranging from moderate to high for most parameters measured. Because apomixis occurs more frequently than sexual reproduction, most heritability estimates should fall closer to the midparent value, resulting in lower heritability. To increase resin and rubber yield in the progeny, selection should focus on plant height and width because these two traits are highly correlated with resin and rubber yield and have the highest heritability of the traits measured.</jats:p>

Assessment, Validation and Application to Real Samples of a RP-HPLC Method for the Determination of Guayulins A, B, C and D in Guayule Shrub

“…It is evident that the continuous rise of interest in the properties of guayulins needs the development of reliable, accurate and sensitive analytical methods for their identification and quantification. Until now, the analytical methods reported in literature for the measurement of the amount of guayulins in Guayule resin [3,4,8,11,13,[17][18][19] or latex [16] are scarce and all lacking of any validation protocol. Obviously, chromatographic methods are dominant in the analytical characterization of such analytes and, among them, HPLC is the preferred approach.…”