2025/12/23 by Ruth A.G. Madrid, Germán Sandoya, D. Calvin Odero · 1 voice
Agricultural and Biological Sciences · #Allelopathy and phytotoxic interactions #Insect-Plant Interactions and Control #Weed Control and Herbicide Applications
paper · doi:10.21273/hortsci19121-25
openalex created_date 2025/12/23 · openalex publication_date 2025/12/23 · openalex updated_date 2026/06/11
The limited availability of novel herbicide chemistries for broadleaf weed control in high-value crops such as lettuce underscores the need to optimize the use of existing broad-spectrum herbicides. This study evaluated 13 lettuce accessions including three commercial cultivars, nine experimental breeding lines, and one PI for tolerance to 12 postemergence herbicides applied at labeled rates for other crops under greenhouse conditions. The primary objective was to identify genotypes exhibiting minimal phytotoxicity and consistent tolerance across herbicide treatments. Nonacetolactate synthase (non-ALS) inhibitor herbicides, including fomesafen (protoporphyrinogen oxidase inhibitor), glufosinate (glutamine synthetase inhibitor), glyphosate (enolpyruvyl shikimate phosphate synthetase inhibitor), linuron and prometryn (photosystem II inhibitors), and mesotrione and topramezone (hydroxyphenyl pyruvate dioxygenase inhibitors), caused severe injury (89%–100%) and significant biomass reduction (>20%) across all genotypes, indicating poor selectivity and limited utility in lettuce production. In contrast, ALS inhibitors flumetsulam, imazamox, imazapic, and imazethapyr (except for rimsulfuron) demonstrated comparatively better crop safety, although tolerance varied among genotypes. Flumetsulam caused the least injury (1%–29%) and maintained higher relative biomass (33%–98%) across most genotypes. A principal component analysis revealed distinct clustering of genotypes based on sensitivity profiles. Breeding lines 49017, 10221, H1098, and 60183 exhibited strong tolerance to flumetsulam and imazethapyr, while line 60150 showed tolerance to all imidazolinone herbicides and flumetsulam, indicating potential sources of multi-herbicide tolerance. Lines 10207 and 60182 were sensitive to all imidazolinone herbicides. A degree centrality network analysis using defined tolerance thresholds (injury ≤20%, biomass accumulation ≥80%) confirmed flumetsulam’s highest connectivity (normalized degree = 1.0), followed by imazethapyr (0.690), indicating their potential for selective use. These findings underscore the importance of genotype-specific herbicide selection and highlight opportunities to leverage genetic diversity to enhance herbicide tolerance in lettuce breeding. The results provide a foundation for future lettuce breeding programs to develop cultivars with improved compatibility to selective postemergence herbicides.