Mitochondrial degradation plays a vital role in seed deterioration. Novel markers were investigated based on a new method for quantifying maize seed deterioration during 12 months’ storage under ambient (lab bench, ~27°C and 50–80% relative humidity (RH)) or controlled ((15±1)°C and (50±5)% RH in bags with low oxygen permeability) conditions involving two techniques: 1) fast ethanol assay and 2) quantitative RT-PCR (qPCR) with four mitochondrial-related genes in maize seed: alcohol dehydrogenase (ADH1), alternative oxidase (AOX1), cytochrome c oxidase (COXc), and ATPase. Ethanol production during imbibition and the expression of genes using the new method were compared to the results of two conventional methods: a germination test and an accelerated ageing test. The results showed that germination following ambient seed storage reduced significantly compared to the controlled conditions, especially at 9 months of storage. Ethanol production of maize seed measured by fast ethanol assay increased during storage. After 6 months, the mean (n=4) ethanol production from seed under ambient conditions was 400 µg L^–1 which was higher than under the controlled conditions (240 µg L^–1). Stored mRNA level of COXc and ATPase significantly decreased over time in ambient storage but were quite stable under the controlled conditions. Maize seed was also treated for artificial ageing at 42°C in 100% RH for 12, 24, and 48 h. At 24 h after treatment (HAT), maize seed produced significantly more headspace ethanol than at 12 HAT and more than the control (non-treated seed). The transcription level of ADH1 and ethanol production increased. The transcription level of COXc was directly related to the severity of the ageing treatment. In conclusion, a combination of fast ethanol assay and qPCR enhanced understanding of maize seed deterioration and provided new possibilities for the evaluation of seed storability based on transcriptional levels.

Low germination and vigor of rice seed associated with dry-seed broadcasting are common problems encountered by rice growers.  The objectives of this study were to evaluate the role of potassium nitrate (KNO₃) on the pattern of seed imbibition and to determine the effect of seed priming with KNO₃ on the germination percentage, speed and uniformity of germination in rice seed.  Experiment 1 compared the patterns of seed imbibition of six concentrations of KNO₃ (0, 0.25, 0.50, 1.00, 1.50, and 2.00%) in two rice cultivars - KDML105 and RD15.  The results showed that soaking rice seed in KNO₃ at higher concentrations could delay the imbibition time.  The higher concentrations of KNO₃ delayed the imbibition time of rice seed and took a longer time to reach the end of phases 1 and 2 compared to the lower concentrations.  The patterns of seed imbibition using distilled water of both rice cultivars (KDML105 and RD15) were quite similar, but with different concentrations of KNO₃, the imbibition time taken to reach the end of phases 1 and 2 was slightly postponed in KDML105 suggesting that different rice cultivars may need different imbibition times for soaking seed in the priming process.  Experiment 2 evaluated the effects of seed priming with 1.0 and 2.0% KNO₃ at different imbibition times.  It was found that priming with 1.0% KNO₃ showed better seed germination than priming with 2.0% KNO₃ and seed priming with 1.0% KNO₃ at the imbibition time of early phase 2 (or 28 h for KDML105) improved seed germination and increased both the speed and uniformity of seed germination.  The results of this study show promise for the use of priming with 1.0% KNO₃ soaked until early phase 2 of seed imbibition for improving the seed germination and vigor of rice in dry seed broadcasting.