LAUSR

BACKGROUND Tipburn is a physiological disorder of lettuce (Lactuca spp.) that causes discolouration and collapse of leaf margins, leading to unsaleable crops in both protected (glasshouse, hydroponic) and outdoor production systems. The occurrence of tipburn is hard to predict and sensitive to environmental conditions. Phenotyping for tipburn resilience requires diverse germplasm resources and to date limited material has been investigated for this condition. RESULTS Using a Lactuca Diversity Fixed Foundation Set (DFFS) under glasshouse conditions, we identified a significant (p<0.001) genotypic effect on tipburn resilience across both the entire population and across lines belonging to the cultivated species, L. sativa, alone. Whilst L. sativa lines exhibited significantly (p<0.05) higher average tipburn severity than those belonging to the wild species L. saligna, L. serriola and L. virosa, we were able to identify both cultivated and wild tipburn-resilient lines. Leaf morphology factors including pigmentation, width and serration also significantly (p<0.05) influenced tipburn resilience. Using a recombinant inbred line (RIL) mapping population derived from two DFFS lines, different small-effect QTLs accounting for 12.3% and 25.2% of total tipburn variation were identified in glasshouse and field conditions, respectively. CONCLUSIONS These results reflect the benefit of phenotyping under production system-specific conditions for the examination of environmentally sensitive traits and highlight genetic markers and germplasm resources for the development of tipburn resilient lines for use in both protected and outdoor lettuce production. This article is protected by copyright. All rights reserved.