Productivity and cytogenetic characteristics of guayule. Screening of plants from the mapimi region

Abstract

Guayule plants were screened in the region of Mapimi (Durango, Mexico) to evaluate physicochemical parameters for selection of increased productivity. The objective was to characterize rubber, and resin content, stem diameter, rubber molecular weight and cytology of these plants to identify and select high productivity sites. Samples were collected from nine locations within the Mapimi Region. Inflorescences containing young floral buds of the same plants were selected to determine ploidy level. Cytogenetic results showed the presence of di‐, tri‐ and tetraploids. Samples for rubber and resin analysis were cut from the branches. Genetic variation in molecular weight and molecular weight distributions for rubber was measured. Significant differences were found in resin content and stem diameter between the sampling sites, but differences were not significant for the rubber content between sites. A productivity parameter was defined and used to identify two locations where guayule genotypes exhibited the best characteristics for commercialization. This information may increase the industrial development and understanding of the polymerization bioprocess.

Induction of tetraploid hardy rubber tree, <i>Eucommia ulmoides</i>, and phenotypic differences from diploid

“…Another plant that produces polyisoprene, guayule, which produces a latex containing cis-polyisoprene as well as resins and triglycerides in its seed oil, is known to generate polyploids spontaneously, and its tetraploids contain more seed oil than diploids (Estilai 1993). However, the rubber content and molecular weight vary by growing site, and differences dependent on ploidy were relatively small (Rodríguez et al 1993). Although studies assessing the effects of different nutrient conditions on the polyisoprene content of E. ulmoides are unknown, and different numbers of chromosomes sometimes cause different metabolic activity (Comai 2005), secondary metabolites, such as rubber and other polyisoprenes, might not be as affected by the number of chromosomes as by nutrients in the soil.…”

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

“…Improvement of guayule is further complicated because of its relatively long generation time (2-5 years) and its complex genetic and reproductive system (Ray et al, 2005;Thompson and Ray, 1989). Guayule has a haploid chromosome number of 18, with a natural ploidy series ranging from diploid to tetraploid or higher (Bergner, 1944;De Rodríguez et al, 1993;Powers, 1945;Thompson and Ray, 1989). In native populations %95% of the accessions surveyed are polyploid, with the majority being tetraploid (Kuruvadi et al, 1997a).…”

“…Despite this apparently narrow genetic base, there appears to be a large amount of variation in cultivated guayule (Ray et al, 2005), not only among lines but also within lines (Dierig et al, 1989a;Naqvi, 1985;Ray et al, 1990). There is also a great deal of unexploited variation available in native populations (De Rodríguez et al, 1993;Kuruvadi et al, 1997b). This variation could be a valuable tool in guayule improvement; however, methods that determine the genetic contribution to this variation and subsequent response to selection need to take into account guayule's unusual mode of reproduction.…”