Seed treatment with Penicillium sp. or Mn/Zn can alleviate the negative effects of cold stress in maize grown in soils dependent on soil fertility

Abstract Maize is becoming an increasingly important crop in northern Europe, but low temperatures during spring may hamper its growth. This effect may be caused by direct plant damage through oxidative stress or indirect damage through decreased uptake of nutrients, especially phosphorus (P), from the soil. Previous studies have indicated that treatment with micronutrients such as manganese and zinc (Mn/Zn), microbial inoculants (biostimulants) or exogenous salicylic acid can alleviate abiotic stress. Seed inoculation with microorganisms can also increase P uptake from the soil. In a pot experiment, we investigated whether the negative effects of cold stress could be alleviated by improving soil fertility (P level), inoculating seed with two different plant growth‐promoting fungi of the genus Penicillium sp., adding extra Mn/Zn at sowing or adding exogenous salicylic acid. These treatments were tested on maize plants subjected to cold stress and two different levels of soil fertility and harvested 28 and 51 days after sowing ( DAS ). We found that the effect of cold stress was not alleviated by improving soil fertility through the use of a more fertile (high P) soil or through fertilisation with plant‐available P in the form of triple superphosphate. Cold stress was also not alleviated by the treatment of seeds with salicylic acid. Addition of Mn/Zn and inoculation with one of the two Penicillium strains tested increased biomass production at 51 DAS (compared with the untreated control) in cold‐stressed plants grown in the high P soil, but not in the low P soil. Thus, addition of Mn/Zn and inoculation with Penicillium sp. can reduce the effects of cold stress in maize plants grown in fertile soil.