Storing Rice Parental Lines Under Mid-Elevation Environment Maintains Seed Germination and Seedling Vigor

Seed storage in cold room is very effective in maintaining high seed viability and seedling vigor of high-value seeds like those of thermosensitive genic male sterile (TGMS) female parent line, albeit this is an expensive strategy. Hence, the study was conducted from September 2017 to September 2018 to determine if seed storage in mid-elevation environment (24°C, 72-90% RH, and 850 meters above sea level) can be a practical approach to maintain seed and seedling qualities of hybrid parental lines. A 3 x 2 x 2 factorial experiment was laid out in split-split plot design with storage environment (ambient room in low elevation, 21 meters above sea level (ARL), cold room in low elevation (CRL), or AR in mid-elevation (ARM) as main plot, storage container (woven polypropylene bag (PB) or hermetic bag (HB)) as subplot, and hybrid TGMS parental line (M20 female parent (S line) or M20 male parent (P line)) as sub-subplot. Seed testing commenced before storage and every month thereafter until 12 months of storage. Seed germination was assessed using in-between paper method, while seedling vigor was evaluated based on seed germination and seedling length values. Results show that seed viability (> 90%) and seedling vigor (10% reduction) across treatments were only comparable until the first month of storage. Germination percentage of S line seeds packed in PB and stored in ARL significantly declined to 85% at 3 months of storage, and further to 16% at 7 months of storage. Interestingly, seeds in HB in ARM storage registered comparable germination percentage (94-95%), seedling height (20-21 cm), shoot dry weight (26-27 mg), and seedling vigor (34-35% reduction) with seeds in CRL until 12 months of storage.