High amylase activity and high ethylene production in rice tolerant of flooding at germination and early seedling stage
2008
Ella, E.S. | Vergara, G.V. | Ismail, A.M., International Rice Research Inst., DAPO Box 7777, Metro Manila 1301 (Philippines)
This study describes rice plant during germination and early seedling stage under flooded conditions. Seeds were sown-dry in pots with soil normally watered or continuously flooded with 8-10-cm tap water depth for 21 d. Elongation growth and levels of amylase activity and ethylene production were measured during the first few days and survival was scored 21 d after dry seedling. Alpha amylase gene expression was analyzed using seedlings grown in sterile solution with different O2 levels. Survival decreased with flooding, with less decrease intolerant genotypes. Flooding increased amylase activity in tolerant genotypes, but there was no change in intolerant ones. Amylase activity at day 3 had strong positive correlations with elongation growth at day 5 (r=0.85 and 0.83 for shoot length and root length, respectively) and also with survival (r=0.92). The gene expression in seedlings grown in sterile hypoxic flask set up was consistent with the amylase activity data. Tolerant genotypes with high amylase activity also had higher RAmy3D amylase gene expression. Ethylene was not detected in dry seeds and even during the first 2 d, but it was detected with prolonged flooding, with greater increase intolerant genotypes starting from day 3. Tolerant genotypes had higher amylase activity in the first few days of growth, had higher ethylene production in the following days, grow faster, and survived better under flooded conditions. high amylase activity and high ethylene production may be associated with high tolerance for flooding at germination and early seedling stage in rice.Future researches of the authors will aim to establish seed management practices that can maximize the expression of these traits under natural field conditions.
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