Temperature regime influences accessions and effectiveness of germination promoters in the high-Andean crop maca

High-Andean crops are precious resources for low-income farmers threatened by climate conditions. In the Puna region of the central Peruvian Andes, poor farmers grow maca (Lepidium meyenii Walpers), a root crop endemic to this region, under extreme environmental conditions. The performance ranking of crop accessions may vary with climate variability due to interactions between genotypes and the environment, but this issue has not been addressed for maca crops. Here we used three thermal setups under laboratory conditions and tested the effects of temperature regime, seed accession, and germination promoters on seed germination and seedling performance traits of maca plants. We found significant temperature × accession (T × A) interactions for most response variables, that is, the performance ranking of accessions varied with temperature regimes. The positive effects of promoters (gibberellic acid, GA; sodium hypochlorite, SH) on germination and seedling emergence variables were not additive and showed a clear trend to be greater at lower temperatures. Because available maca accessions still require the Andean Puna´s cold environment to develop their hypocotyls fully, the selection of accessions with better tolerance to higher temperatures should be taken as a long-term challenge. In the short term, our findings strongly suggest that maca growers might use GA as a promoter to overcome limitations imposed on seed germination and seedling emergence by low temperatures at the crop-growing areas.