Dragon's head (Lallemantia iberica) as an oilseed crop has been recently introduced to Iranian farmers and due to its tolerance to abiotic stresses grown in drylands and rain-fed areas of the country in rotation with cereals and pulses. In this study, fifty Iranian L. iberica landraces were evaluated for the prevalent diseases under field conditions during 2019-2021 in Gonbad-Kavous, North of Iran. A spot lesion/blight symptom was observed in the field and the subsequent classical and molecular mycological studies identified Alternaria tenuissima and A.atra as the causal agents. Subsequently, a complimentary experiment was conducted to screen genotypes for these disease agents under controlled conditions using the proposed scoring system invented in this study. Results showed a significant negative correlation of Sclerotinia stem rot with yield and plant height, while no relationship was observed between Alternaria spot/blight and agronomic traits. Two and twenty-one genotypes were identified as highly resistant and resistant to Sclerotinia stem rot in the field, respectively; where six of them showed additional resistance to Altarnaria spp. in the glasshouse. The resistant/high-yield genotypes identified through this research can be considered valuable sources to be released as new cultivars or exploited in breeding programs.