D. Jasso de Rodríguez

Correlation and path coefficient analyses of the agronomic trait of a native population of guayule plants

Abstract Correlation and path coefficient analyses have been successfully used for plant selection for increasing yields of different crops. This approach could be applied to increase guayule latex production. Natural stands of guayule ( Parthenium argentatum ) in Mexico may constitute a source for plant selection. This paper reports on the correlation coefficients for phenotypic characteristics and path coefficient analysis of guayule to evaluate the direct and indirect effects of the rubber production components. The variables evaluated were plant height, main stem diameter, dry weight, rubber and resin content, and yields. These were measured from different part plants of shrubs a wild stands of Gomez Farias, Mexico. Rubber yields of the first-year stem and the diameter of the main stem are the variables that relate to rubber yield per plant. Based on the correlations and path coefficient analysis results, we found that the dry weight of the first-year stems is a good indicator for selecting high rubber yielding plants in wild stands.

Multimodal molecular weight distributions of guayule rubber from high rubber yielding lines

Abstract Molecular weight distribution (MWD) of guayule rubber extracted from well characterized, high rubber yielding plants, grown under controlled and natural conditions were observed to be multimodal (especially in young plants). The MWD curves apparently depend on genetic and environmental inter-relations, which have not been established. We believe that multimodal curves may reflect a “batch type” polymerization process which could be triggered by rubber-synthesizing enzyme activities, depending on genetic and environmental factors.

Rubber yield and guayule populations' attributes in naturally reestablished wild stands in México

Abstract Medical latex goods provide opportunity for the commercial exploitation of hypoallergenic guayule (Parthenium argentatum, Gray). This, however, requires an adequate latex supply. Wild stands of guayule exist in Mexico. These have naturally reestablished over the last 15 years from previous harvesting of the whole plant. These stands constitute an excellent source of genetic material for selection, cropping and industrialization of guayule. The objectives of this study were: (a) to evaluate plant density and the spatial distribution pattern of the naturally occurring guayule shrubs in two types of topography within a wild stand at the Gomez Farias locality, at Coahuila, Mexico; (b) to determine the effect of main stem diameter on biomass, rubber and resin content, rubber and resin yield, and height for plants naturally occurring in slopes of less than 8% (Site A) and between 8 and 20% slope (Site B); and (c) to correlate total rubber yield with the other variables. Plant density was evaluated using the point centered quarter (PCQ) method based on a sample size of 40 random points per site. The spatial distribution pattern was estimated by the block quadrant variance method with two 64×3 m belts at each site. Production variables in the Site A were evaluated from 45 shrubs classified into three diameter classes according to the shrubs dominant sizes. The Site A had a total shrub density of 7890 plants/ha, whereas the Site B had 31 900 plants/ha. The distribution of guayule plants was uniform for the Site A and clumped for the Site B. The plant branches showed high biomass production and the greatest rubber content was found in the main stem. Resin content was higher than rubber content in all the three diameter classes with a high positive correlation between these two parameters.

Rubber and resin contents of native guayule germplasm of Mexico

Abstract Plant germplasm obtained from the origin of the genetic material can be useful for varietal improvement. For guayule (Parthenium argentatum Gray.) germplasm, 343 accessions were collected from 53 locations in 20 municipalities within five provinces (Coahuila, Durango, Nuevo Leon, San Luis Potosi and Zacatecas) in Mexico. Rubber and resin contents were determined for these accessions to identify high rubber yielding lines, to locate potential areas of guayule population for future exploitation and to determine correlations between different pairs of characters. The number of accessions collected at each location varied from 3–10. The analysis of variance for rubber and resin concentrations, plant height and spread showed significant differences between populations (locations) indicating the possibility of selecting high rubber yielding genotypes. The plant collections made from Coahuila and Durango provinces had the highest rubber and resin content, compared to the other provinces in Mexico. The rubber content ranged from 1.4–9.8% with a mean of 3.7%; the resin content from 5.2–12.4% with a mean of 7.5% for Coahuila province and ranged between 2% and 9.6% and averaged 5.8% for Durango. The average rubber percentages were 1.6%, 2.3% and 2.1% from the Nuevo Leon, San Luis Potosi and Zacatecas collections, respectively. We identified 15 superior genotypes with a rubber accumulation between 8 to 10%, which all came from the Coahuila and Durango provinces. A positive, significant correlation was obtained between rubber concentration with three characters, namely, percent resin, plant height and top spread in guayule.