Lethal dose 50 of NaCl and ethyl methanesulfonate in jalapeño pepper (Capsicum annuum L.) seedlings and tolerance to salinity

Soil salinity is a factor affecting crop production and yield. An estimated 74% of agricultural soils are saline, a problem that could be aggravated due to climate change. Our goal was to determine the lethal dose 50 (LD₅₀ ) of NaCl and ethyl methanesulfonate (EMS) in jalapeño pepper (Capsicum annuum L. cv. Jalapeño M.) for selecting putative salt-tolerant mutants. Root length was used as an indicator of the LD₅₀ of NaCl in seedlings cultured for 35 days in MS medium containing 0 (without NaCl), 50, 100, 150, 200, or 250 mM NaCl and germination rate as an indicator of the LD₅₀ of EMS in seeds exposed to 0% (without EMS), 0.01%, 0.1%, 0.25%, or 0.5% EMS for 3 and 6 h. We selected salt-tolerant seedlings after 35 days in medium with the determined LD₅₀ of NaCl. Canonical and probit analyses to the LD₅₀ of NaCl and EMS results and multinomial linear regression for germination and survival were applied. LD₅₀ of NaCl (150 mM) and EMS (0.3%) were determined. Seed exposure to 0.5% EMS for 6 h reduced germination (67%) and seedling survival (18%). We obtained four putative salt-tolerant mutants by culturing in medium containing the LD₅₀ of NaCl, two from seeds exposed for 6 h to 0.01 EMS, and one each from of the seeds treated with 0.1% or 0.5% EMS. The results show that it is possible to select putative salt-tolerant mutants of jalapeño pepper through mutagenesis with EMS and in vitro culture in media containing the LD₅₀ of NaCl.