Manganese is an important micronutrient for many plants, and barley in particular. Spotting that a plant has a manganese deficiency can be difficult. By the time you see there’s a problem it’s already very serious. Often farmers apply sprays before manganese deficiency is apparent, which is expensive. To combat this, Jonathan Cope and colleagues have been examining barley through the Scottish landrace Bere. They set out to confirm that Bere had traits for using manganese efficiently, and identify genetic loci associated with these traits.
To test the barley plants, the scientists were installed into a hydroponic system, so the access to trace elements could be carefully controlled. The uptake and use of manganese was tracked using chlorophyll fluorescence. This is a technique that botanists have used to track manganese deficiency before it becomes apparent to the naked eye.
The scientists found the Bere barley outperformed the other varieties of barley when it came to manganese use efficiency. Looking at the genomes of the plants, they also found genetic markers that correlate with this trait.
“Analysis of the Mn concentration in the shoot biomass showed that an increased level of accumulation of Mn in the biomass corresponded to increased Mn use efficiency, and that this occurred even when there is an adequate supply of Mn in the environment,” write the authors. “All lines/cultivars showed large decreases in Mn content when grown in Mn-deficient conditions, but Mn-efficient Bere lines presented a concentration large enough to avoid the specified critical deficiency threshold concentration of Mn in shoot tissue… In contrast, the elite cultivars had Mn concentrations that were well below this critical value.”
Manganese may not be a well-known element, but it provides protection against oxidation for a plant. This is important, given that leaves strip carbon from carbon dioxide, leaving oxygen behind to cause damage.
“The increase in Mn use efficiency in an elite background without compromising the yield quantity or quality would allow the growth of elite barley in marginal lands that could previously not economically support elite cultivars.” write Cope and colleagues. But it doesn’t just open new land for growth they say. “Furthermore, it would provide a buffer to changing environments, preventing deficiencies without the need for routine blanket spraying of Mn foliar fertilizer and thus saving money on purchase and deployment of the chemical.”