Associative transcriptomics in Brassica napus suggests a role for Arabidopsis Response Regulator orthologs in seedling vigour

Background and Aims Optimal seedling vigour determines successful crop establishment and its ability to overcome abiotic and biotic threats. Seedling vigour is regulated by several different factors, genetic, physiological, environmental, post-harvest storage, making it challenging to fully elucidate. The aim of this study was to dissect the genetic basis of post-germinative seedling traits and its implications in seedling establishment success in Brassica napus . Methods A B. napus diversity set panel was used to phenotype seedling establishment traits in the soil including days to emergence, days to appearance of first and second true leaves, and days to reach 25% and 50% cotyledon expansion. An associative transcriptomics analysis was performed to identify the genetic factors regulating seedling establishment. Key Results The study of different phenotypic traits highlighted the relevance of scoring more than one trait to determine good performers. Gene expression markers significantly associated with the studied traits were associated with the cytokinin signalling pathway and photomorphogenesis. Gene expression markers for orthologues of Arabidopsis thaliana RESPONSE REGULATOR 4 and 5 (ARR4, ARR5) were significantly associated with days to appearance of second leaf. SUPPRESSOR OF PHYA-105 1 ( SPA1) orthologues were associated with cotyledon area, meanwhile ALTERED SEED GERMINATION 7 ( ASG7 ) and PSEUDO-RESPONSE REGULATOR 7 ( PRR7) orthologues were associated with days to emergence, suggesting a complex and interconnected regulatory pathway controlling several traits of seedling establishment. Conclusions These results uncovered promising genes that appear to work in a complex and interconnected manner controlling several post-germinative seedling traits affecting final seedling establishment speed.