Can chlorophyll flourescence be used to determine the optimal time to harvest rice seeds for long-term genebank storage
2014
Timple, S. | Hay, F.R. | Van Duijn, B.
The potential use of chlorophyll fluorescence (CF) to determine the optimal time to harvest rice seeds when their longevity in genebank storage would be maximized, was examined using 20 diverse accessions from the International Rice Genebank at IRRI. The rice accessions were planted during the 2013 dry season and harvested at 24, 31, 38 and 45 days after peak flowering. After threshing and drying, half of each seed lot was hand-sorted by genebank staff. Comparative longevity experiments were conducted to seeds at different maturities, after hand-sorting. At an adjusted seed moisture content of 10.9% (% fresh weight basis), the seeds were stored at 45 deg C to induce accelerated ageing. Samples were taken every 3 days for up to 60 days for viability monitoring through a standard germination test and the time for viability to fall to 50% (p 50), as a measure of seed longevity, determined. Seed longevity generally increased during seed development, with p 50 increasing by between 42.8 and 348.6%. Hand-sorted and non-sorted samples of the seed lots were analyzed for CF analysis using the Seed analyser (Fytagoras, Leiden, the Netherlands). CF curves (number vs pico-amps) showed distinct peaks but were significantly skewed. The position of the peak and area under the curves (total CF) varied depending on the accession, maturity and whether or not the seeds had been manually sorted. Total CF was generally highest in the least mature seeds and decreased with increasing maturity (by between 0.25 and 6.30%, depending on accession). The position of the peak shifted downward by between 60 and 1050 pA as maturity increased between 24 and 45 DAF. Based on the CF and comparative longevity results, the potential use of CF to improve genebank operations are discussed.
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