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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Sustainable Agricultural Systems Laboratory » Research » Publications at this Location » Publication #317506
Title: Seed dormancy is modulated in recently evolved chlorsulfuron-resistant Turkish biotypes of wild mustard (sinapis arvensis)

Author
item TOPUZ, MUHAMET - Former ARS Employee
item NEMLI, YILDIZ - Ege University
item FATIMA, TAHIRA - Former ARS Employee
item Mattoo, Autar

Submitted to: Frontiers in Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2015
Publication Date: 7/24/2015
Citation: Topuz, M., Nemli, Y., Fatima, T., Mattoo, A.K. 2015. Seed dormancy is modulated in recently evolved chlorsulfuron-resistant Turkish biotypes of wild mustard (sinapis arvensis). Frontiers in Chemistry. 3:46.

Interpretive Summary: Major obstacles to increasing crop productivity include weed competition, and maintaining seed vigor of the cash crop upon storage since seed germination decreases upon aging. Wild mustard is a prolific weed in wheat fields and its management has involved the use of chlorsulfuron herbicides that inhibit acetolactate synthase (ALS), a rate-limiting protein in the synthesis of three prominent branched-chain amino acids. However, resistance to chlorsulfuron among weeds has been observed worldwide, including recently in wheat fields in Turkey. We show and confirm that the newly evolved resistance to chlorsulfuron in Turkish biotypes is associated with altered target site mutations in the ALS gene in line with previous reports. Further, we show an additional phenotype of chlorsulfuron resistant wild mustard biotypes in the form of an altered seed dormancy behavior compared to the susceptible biotypes. Dry storage (after-ripening), had a differential effect on the germinability of seeds from susceptible versus resistant wild mustard biotypes. The Turkish chlorsulfuron-resistant wild mustard seeds upon dry storage, gradually develop the ability of higher germination rate than the susceptible biotypes, and their faster germinability was sustained over a longer duration of 4-8 years. These studies demonstrate that the altered target site trait conferring resistance to chlorsulfuron in ‘R’ biotypes does not result in a growth penalty. The relevance of herbicide resistance is of tremendous concern for weed management including the possibility of their altered ecological fitness in regard to their growth, competitive ability and seed production and seed germination ability. These studies are of relevance to ecological fitness of herbicide-resistant biotypes in terms of seed viability and germination, and will be of interest to weed ecologists, wheat growers, plant physiologists and geneticists.

Technical Abstract: Biotypes of the broad-leaved wild mustard (Sinapis arvensis L.) found in wheat fields of the Aegean and Marmara regions of Turkey, were characterized and shown to have developed resistance to sulfonylurea (chlorsulfuron), an inhibitor of acetolactate synthase (ALS). DNA sequence analysis of the ALS genes from two such resistant (‘R’) biotypes, KNF-R1 and KNF-R2, revealed point mutations, CCT (Pro 197) to TCT (Ser 197) in KNF-R1 and CCT (Pro 197) to ACT (Thr 197) in KNF-R2; these substitutions are consistent with the presence of chlorsulfuron-insensitive ALS enzyme activity in the ‘R’ S. arvensis biotypes. An additional phenotype of chlorsulfuron resistance in the Turkish S. arvensis ‘R’ biotypes, was revealed in the form of an altered seed dormancy behavior over 4 to 48 months of dry storage (after-ripening) compared to the susceptible (‘S’) biotypes. Seeds of the ‘S’ biotypes dry stored for 4 months had a higher initial germination, which sharply decreased with storage time, while the seeds of the ‘R’ biotypes had lower germination after 4-months storage, rising sharply and peaking thereafter by 24 months of dry storage. The ‘R’ biotype seeds continued to maintain a higher germination percentage even after 48 months of after-ripening. The seed weight of ‘R’ and ‘S’ biotypes after-ripened for 4 months was similar but those after-ripened for 48 months differed, ‘R’ seeds were significantly heavier than those of the ‘S’ seeds. Differential seed germinability between ‘S’ and ‘R’ biotypes was found not a case of differential viability, temperature regimen or non-response to pro-germination hormone GA3. These studies are of relevance to ecological fitness of herbicide-resistant biotypes in terms of seed viability and germination.