1a.Objectives (from AD-416):
California leafy vegetables have one or two key herbicides, which could be lost due to high manufacturing and regulatory costs. There is no effective post-emergence herbicide against broad-leaf weeds for lettuce and spinach. It is essential to find dependable and sustainable weed control strategies to prevent crop loss. We propose to develop herbicide-tolerant lettuce and spinach through conventional breeding. It will reduce herbicide use by replacing high rate herbicides with low rate products.
1b.Approach (from AD-416):
In the first year, we will treat lettuce and spinach seeds with ethyl methane sulfonate to generate new germplasm. Treated seeds will be planted to produce progeny for screening with glyphosate (Roundup) herbicide. We will also screen spinach germplasm for tolerance to linuron, prometryn and bentazon herbicides, as varietal differences in tolerance have been reported. Putative tolerant lines will be tested in the second year to confirm the results. We will also start to study the inheritance of the trait. If only partial tolerance is found, these plants will be crossed to each other to increase the level of tolerance. If the tolerance exists only in wild species, backcrosses will be used to transfer the trait into cultivars. Herbicide-tolerant lines will be evaluated in the field in Salinas, Central, and Imperial Valleys in the third year to demonstrate the results to the industry and seed companies, through which seeds of herbicide-tolerant cultivars will be made available to growers.
This project contributes directly to the objectives 1 and 3 of the parent project, genetic improvement of lettuce and spinach. Weeds in leafy vegetables increase production costs and reduce yields and quality; sometimes resulting in 100% yield loss. Lettuce and spinach growers in California have one or two key herbicides for each crop, and these old herbicides have low sales volumes but high regulatory costs for registrants to keep selling them. The loss of pronamide registration for leaf lettuce in 2009 has increased production costs by over $200/acre. We will create sustainable weed management systems by developing herbicide-tolerant lettuce and spinach germplasm through conventional breeding. We have hired a Postdoctoral Research Associate to work on the project. The goal of the project for the next reporting period is to generate lettuce and spinach mutants with herbicide resistance by treating seeds with a chemical mutagen, ethyl methane sulfonate (EMS).