Mapping Chilling Tolerant Photosynthesis in an Interspecific Miscanthus population

An F₂ mapping population (10UI-009) was developed by crossing Miscanthus sacchariflorus 'Robustus-Bluemel' and Miscanthus sinensis var. condensatus 'Cosmo Revert'. PSII maximum efficiency (Fv/Fm in dark-adapted state) was measured in 325 F₂ seedlings using a Chlorophyll Fluorescence Imaging System (Technologica). Seedlings were examined after 7-days growing in control conditions (25 °C/20 °C day/night), and on the 3^rd and 7^th day of low temperatures treatment (10 °C/5 °C day/night). Three categories of phenotypic data were evaluated: (1) Percent Fv/Fm values retained after seven days of chilling treatment (2) Recovery Fv/Fm: percent retained after seventh day of chilling treatment minus percent retained after third day of chilling treatment and (3) High & stable Fv/Fm (<5% change). Plants were divided into best and worst performing based on these three phenotypic categories. RAD-seq (Restriction Associated Digestion-sequencing) was performed on total of 49 plants (best and worst for each of the three traits) and parents. After filtering the dataset, 2129 markers were aligned to the Sorghum bicolor genome. Preliminary analysis using ANOVA to compare the best and worst plants with RAD-Seq data revealed significant SNP associations with the second trait. Selected plants were further grown and divided into 3-4 replications. Currently, measurements are being made on mature replicated plants, for leaf photosynthetic gas exchange (net leaf CO2 uptake (Asat), conductance) and modulated chlorophyll fluorescence [maximum operating efficiency of photosystem II (ФPSII)] using an LI-6400 (LI-COR) in warm conditions (25 °C/20 °C), and then during and following a chilling treatment of 10 °C/5 °C for eight days in controlled environment chambers.

Key Words: Miscanthus, Chilling tolerance, RAD-seq, LI-COR, SNP, Association analysis