2017 ASHS Annual Conference

Tomatoes (Solanum lycopersicum L.) are consumed and produced globally. In 2014, the US produced 12,574,550 tons of tomatoes, ranking 2^nd globally in production after China. Tomato is the nation's fourth most popular fresh-market vegetable based on consumption. In Mississippi it is grown on over 444 acres across 627 farms. Commercially, weeds are controlled using herbicides. However, herbicide options are limited because tomatoes are sensitive to herbicide damage. Yield can be reduced up to 25% because of herbicide drift from auxins and glyphosate. Injury on tomatoes from auxin herbicides and glyphosate was caused at rates as low as 1% concentration. This causes significant reduction in yield and plant growth and has therefore discouraged both field and greenhouse tomato production especially in the Mississippi delta region where aerial herbicide applications to field crops are common. Tomato’s diverse germplasm, including wild relatives, are known to be tolerant to numerous biotic and abiotic stresses. Chemical stress is an abiotic stress, and wild tomato accessions may have natural tolerance to herbicides in addition to other abiotic stresses. Thirty-five tomato accessions were evaluated in a greenhouse at Mississippi State University for tolerance to various herbicides. The best of these were then taken to the field for evaluation at both the North Mississippi Research & Extension Center in Verona and the Truck Crops Branch Experiment Station in Crystal Springs. The field experiments included 10 accessions and five herbicides in a randomized complete block design with three replications. Drift was simulated by mixing herbicides at 1% strength and applying them seven days after transplant (DAT) with a CO₂ backpack sprayer. Visual injury (on a scale of 0-100%), plant height, and chlorophyll content were recorded weekly from 7 to 56 DAT. At harvest, tomato fruits were graded, and yield per plant was measured. Among the accessions screened, TOM18 AND TOM35 were tolerant to dicamba demonstrating significantly less injury and similar fruit yield compared to Better Boy. Additionally, TOM129 showed significantly less injury and higher yield compared to Better Boy when treated with quinclorac herbicide. Results from this study will demonstrate the level of diversity within and among herbicide-tolerant populations of tomato accessions. A highly diverse population of tomato is preferred for tolerance screening with additional herbicides, as they will have a higher degree of adaptability to herbicide and abiotic stress. These tomato lines can be further used in breeding programs to develop herbicide-tolerant varieties.