Analysis of stress indicators during cryopreservation of seeds of landrace maize (Zea mays)

BACKGROUND: Maize breeding programs focus on the development of hybrid varieties and the cultivation of landrace materials is discouraged; however, they are a valuable source of genes and their conservation is advisable. OBJECTIVE: Analyzing some stress indicators during cryopreservation of maize landrace seeds. MATERIALS AND METHODS: Seeds of 35 accessions of landrace maize were collected in two regions of Costa Rica and cryopreserved by direct immersion in liquid nitrogen (LN). Membrane integrity, germination of seeds and DNA methylation in tissues were analyzed 5, 7 and 9 days after rewarming. RESULTS: Germination of landrace maize seeds was near 100% for most accessions. No statistically significant differences in germination were observed between non-cryopreserved controls and seeds stored in LN for 1 h or 1 year. Membrane integrity, number of leaves and root and shoot length of plantlets were similar after cryostorage of seeds for 1 h and 1 year. A short delay in growth of cryostored seed compared to non-frozen controls was observed. Changes in the proportion of DNA methylation were noted from 0 to day 9 in the organs studied depending on the germination stage and cryopreservation treatment. CONCLUSION: It may be inferred that many of the methylated genes were related to growth and development. In addition, a cryobank of maize landraces from two regions of Costa Rica was established.