Impact of water stress during reproductive development on seed dormancy in Bromus diandrus Roth and Lolium rigidum Gaudin

Abstract

Context Bromus diandrus Roth and Lolium rigidum Gaudin are important weeds of cereal-based cropping systems of Australian agriculture. Adaptation to environmental stresses, protracted seed germination and herbicide resistance have made these weeds serious threats to crop production. Aims Studies were undertaken to determine the impact of moisture stress during reproductive development on the extent of seed dormancy and the expression of genes involved with gibberellic acid and abscisic acid synthesis. Methodology A pot study was undertaken at two locations, with two populations each of B. diandrus and L. rigidum. Water stress was applied from either the GS31 or GS60 stage until seed maturation, along with a well-watered treatment. Seeds of stressed vs well-watered treatments were assessed for seed dormancy and the expression of ABA1 and GA20ox genes using quantitative polymerase chain reaction. Results The seeds from GS31 treatment, where plants experienced the longest water stress, were most dormant in both weed species. Water stress treatments altered the expression of the GA20ox gene, which was correlated with the level of dormancy in seeds of B. diandrus and L. rigidum. Conclusions This investigation has provided clear evidence of the impact of water stress on seed dormancy and on expression of genes involved in regulating seed dormancy in these weed species. Implications As spring rainfall in the Australian agricultural landscape is highly variable, weeds are likely to experience variable levels of water stress during reproductive development, which in turn is likely to influence seed dormancy, weed seedling emergence and effectiveness of pre-sowing weed management next season.