Identification of Resistance Sources Against Orobanche Cernua in Tobacco Germplasm

This study investigates the genotype × year interaction in tobacco plants facing the threat of Broomrape (Orobanche spp.), a parasitic weed impacting tobacco production. Over two years, 67 tobacco genotypes were assessed separately under normal and O. cernua-infected conditions using a randomized complete block design with three replications. Measurements included plant height, leaf area, number of leaves, leaf fresh weight, and leaf dry weight for tobacco plants. Additionally, parameters for O. cernua, such as the number of broomrapes per pot, broomrape fresh weight, and broomrape dry weight, were recorded. Mixed linear analysis of variance revealed significant differences (LRT_env) for all traits, signifying distinctions between normal and infected conditions. LRT_ge, indicating genotype × year interaction, was significant for plant height and leaf dry weight. Notably, the study identified tobacco genotypes with stable leaf dry weight over two years under both conditions, with G28 and G29 displaying the highest values. Broomrape growth characteristics varied among tobacco genotypes, and immune types such as G11, G17, and G59 were identified. GGE biplot analysis highlighted differences in tobacco germplasm performance across years and planting conditions. The stability parameter (weighted average of absolute scores, WAASB) was computed, and a biplot of leaf dry weight × WAASB identified G18, G1, G6, G65, G25, G66, G67, G14, and G11 as top-performing genotypes. Using MTSI as a selection index, G16 emerged as the most ideal stable genotype, followed by G29, G25, G11, G4, G65, G28, G64, G44, and G41, exhibiting favorable selection differentials for all traits. This study successfully identifies genotypes with notable resistance levels and stability across diverse years, offering valuable insights for tobacco breeding programs.