A simple staining method for observation of germinated Striga seeds

Summary

In vitro techniques are essential for Striga research and the development of appropriate control methods. In the laboratory, pre-screening of non-host or false-host plants of Striga for trap cropping or the screening of hosts for resistance involves visual evaluation of Striga seed germination that may be stimulated by plant parts or root exudates. This technique is presently laborious because the small Striga radicles are colourless. A number of solutions were evaluated to visualize the radicles of Striga hermonthica to obtain a reliable, simple and fast staining method yielding good contrast for visual observation, with readily available, inexpensive and minimally toxic dyes and staining solutions. The inks Brilliant Blue (Pelikan), Blue (Geha) and Brilliant Green (Pelikan), in either vinegar or lactic acid, produced radicles with excellent contrast, whereas radicles stained with Brilliant Red (Pelikan), Black (Sheaffer), Brilliant Black (Pelikan) gave good contrast. Striga radicles stained with Aniline Blue in vinegar or lactic acid, or Coomassie Brilliant Blue R250 in lactic acid, showed excellent contrast. Radicles stained with Ink Black (Sheaffer), Cotton Brown, or Rubin S in either vinegar or lactic acid also showed good contrast. With water as the diluent, only Lactophenol Blue showed excellent contrast. For health, safety and environmental concerns, availability and staining time, Blue ink in household vinegar (5% acetic acid) appears to be an excellent dye for Striga radicles and could be used in routine Striga germination assays