Raiders of the Vavilov ark: sleuthing new photosynthetic traits from the past

Estavillo GM1, Do NL1, Blake C1, Harding C1, Zwart A2, Voss-Fels KP5, Barrero-Sanchez JM1, Hickey L5, Sharwood R3, Kramer DM4 and Condon AG1

  1. CSIRO Agriculture & Food, Canberra, ACT 2601, Australia.
  2. CSIRO Data61, Canberra, ACT 2601, Australia.
  3. The Australian National University, Canberra, ACT 2601, Australia.
  4. Michigan State University, East Lansing, MI 48824, USA.
  5. QAAFI, The University of Queensland, St Lucia, QLD 4072, Australia.

Improving photosynthetic capacity is seen as an obvious target for increasing total crop biomass and yield. However the complexity of photosynthesis and lack of high-throughput screening methods hampers the identification of genotypes with improved carbon fixation rates. We have used an affordable, hand-held chlorophyll fluorescence spectrometer (PhotosynQ) to screen for genetic diversity of photosynthetic traits in a set of wheats pre-dating modern breeding (from the Vavilov collection). There was a large range in the rate of linear electron flow (LEF) among 60 selected Vavilov entries representing the whole genetic diversity of the panel. LEF varied from 21 to 80 μmol m-2 s-1 at low light, and from 72 to 167 μmol m-2 s-1 at five times higher irradiance (high light). Additionally, there was large variation in the magnitude of the change in LEF from low to high light, suggesting the presence of plasticity to light acclimation among these lines. There was also considerable variation in how light-derived energy was apportioned between photochemistry and other energy dissipation mechanisms (i.e., heat loss). Concurrent gas exchange, coupled with conventional chlorophyll fluorescence measurements and biochemical analyses were also performed on flag leaves of some selected lines. The results indicated that PhotosynQ could be deployed as a useful screening tool for photosynthetic traits and that screening novel genetic resources could enable the discovery of new traits or enhanced expression of existing traits to improve wheat photosynthesis.