Resin production of Grindelia accessions under cultivation

In the early 1980's. Grindelia camporum (Asteraceae) was proposed as a potential resin crop for and lands. A field experiment was conducted in Arizona to evaluate eight Grindelia accessions that included two accessions of G. camporum (native to California's Central Valley, and known to differ in earliness of flowering), Grindelia stricta var. platyphylla and G. stricta var. stricta (both native to saline estuaries in northern California) and four accessions of Grindelia chiloensis from the coastal region of southern Argentina. Two plots were established in September 1994, with a total of 2176 plants. Crude resin (CR) content was highest for all four accessions of G. chiloensis, with the tetraploid accessions having the highest CR contents. G. camporum and G. stricta var. platyphylla were intermediate in CR content. CR content in G. stricta var. stricta was 3.3%. In general, CR contents were lower than previously found for these species. A possible explanation for this is a reduction in resin production due to high water and nutrient availability. Biomass production was significantly different among accessions. The highest biomass production for the first harvest was found for G. stricta var. platyphylla (517 g/plant). The two tetraploid accessions of G. chiloensis (accessions 333 and 336) yielded around 200 g/plant. Biomass production of the tetraploid accessions of G. chiloensis was significantly higher than thai of the diploid accessions of the same species. This yield was about one-half of that for G. camporum. Grindelia stricta var. stricta biomass production was the lowest of the eight accessions (119 g/plant). At second harvest (November 1995), individual plant biomass was equal to or smaller than the first harvest for most accessions except for G. chiloensis 297 and 336. When biomass production and resin content were combined for both harvests, G. chiloensis tetraploid accessions emerged as the highest resin yielding genotypes.