Large-scale commercial production of this crop presents unique challenges because of the plants indeterminate vegetative growth, lack of concentrated flowering and seed set and non-uniform seed maturation. Since 1984, we have investigated borage seed production and GLA metabolism. Field studies were conducted to determine the optimum plant population and nitrogen levels and a prototype mechanical harvester to vacuum seed from the soil surface was built. Experimental seed yields of 753 kg/ha were obtained when multiple nondestructive harvests of seeds were periodically collected from the soil surface, plus a single destructive harvest where plants were cut and seeds harvested. Simulation of a single destructive harvest yielded only 35-40% of the total potential seed yield because of significant seed loss due to seed shattering.
Borage is susceptible to a wide range of insects and disease pests, and is a weak competitor with weeds. Supporting weed control studies identified several promising preemergent herbicides and other compounds that could eradicate the plant No satisfactory postemergent herbicides were identified.
Studies on the genetic variation of seed lines indicated a wide range of total fatty acids and GLA content. Nonshattering types were not found among the more than 50 accessions evaluated. The development of nonshattering seed fines high in fatty acid and GLA would overcome the present production limitations. However, in the interim, the refinement of a seed harvesting unit which can follow a mechanical combine could make the commercial production of borage a more attractive enterprise.
Following an eight year breeding program we have, developed pyrethrum (Chrysanthemum cinerariaefolium) germplasm adapted to environmental stresses inherent to desert irrigated agriculture. Moderate winters, combined with wide differences in day/night temperatures (a result of the dry desert climate) somewhat mimic the high elevation equatorial environments of East Africa and Equador where high pyrethrin contents are achieved. Arid adapted, stress-resistant pyrethrum clones have been bred which show a good balance of pyrethrins and which yield greater than 2% pyrethrins (dry weight basis) analyzed by HPLC. At Arizona latitude, pyrethrum behaves as a perennial showing a single flush of blooming in April. Simultaneous flowering makes mechanized harvesting feasible. Favorable climatic conditions coupled with intensive irrigated agriculture technology of the American Southwest make it probable that C. cinerariaefolium will become a viable perennial crop in Arizona. It is hoped that our work will promote new domestic production of this high value insecticide crop.