Assessing different physiological, seed yield and quality responses of camelina lines to drought

Camelina sativa (L.) Crantz is recognized as one of the most drought-tolerant Brassica oilseed species, yet variability in the response to stress among different genotypes remains underexplored. With the aim of investigating the response of four different camelina lines (UNT4, UNT18, UNT21 and UNT46) to drought, they were tested in twenty-four lysimeters under favorable (21 % volumetric water content, VWC) and drought (9 % VWC) conditions, imposed from the start of flowering. Physiological parameters were measured to identify possible different response mechanisms at early stage. All the surveyed parameters were significantly affected by the imposition of water stress and lines, but only some variables (i.e., A, gs, and iWUE) were affected by the interaction "line x stress", revealing differences in their stress response behavior to drought. Indeed, although UNT18 was the line showing the lowest reduction of physiological parameters under drought, it was one of the less productive lines considering seed yield, reporting 0.25 g/plant in control conditions and 0.16 g/plant in drought. Otherwise, UNT46 showed a higher tolerance to drought with surprisingly significantly higher seed yield under drought (0.44 g/plant) than in well-watered conditions (0.26 g/plant), and this was detectable at earlier stage by an increased intrinsic water use efficiency. A complex and diverse response mechanism to drought in the studied lines emerged. UNT46 and UNT21 showed a trade-off between seed size and weight, whilst UNT4 showed a restricted response to drought stress at physiological level, despite being severely impacted in terms of yield. Interestingly, among physiological parameters surveyed early after stress imposition only leaf fluorescence (Fv/ Fm) resulted significantly and negatively correlated with final seed yield (r = -0.59), while seed oil content resulted highly correlated with many of them, particularly with silique walls gs (r = 0.65). In conclusion, UNT46 and UNT21 had the best performance under drought being able to keep stable their seed yield, presumably in relation to the capacity to produce a higher number of siliques, which were actively contributing to photosynthesis.