Cultivar-specific seedling vigor and expression of a putative oxalate oxidase germin-like protein in sugar beet (Beta vulgaris L.)

For genetic screening and breeding purposes, an in vitro germination system that reflects relative field emergence potential was used to screen for germination-enhancing and stress-induced genes from germinating seedlings from two varieties of sugar beet. Three full-length germin-like protein (GLP) gene classes were recovered from stress-germinated seedlings of a superior emerging variety. GLP gene expression, oxalate oxidase protein activity, the H₂O₂ content of stressed seedlings, but not catalase activity, were induced by stress germination conditions (e.g. excess water, NaCl, mannitol, or oxalate) in a good emerging hybrid and were not induced in a poor emerging variety. Only one of the three germin-like protein genes (BvGer165) was differentially regulated, and was induced only in the good emerger. Hydrogen peroxide promoted germination and partially compensated solute-depressed germination percentages. Unlike other solute recovery by hydrogen peroxide regimes, recovery in oxalic acid plus H₂O₂ was cultivar-independent. A block in oxalate metabolism is postulated to contribute to lower germination under stress in the lower emerging variety. Selection for stress-induced germin expression, or for down-stream targets, presents the first direct target to enable breeding for improved field emergence of sugar beet.