Abstract
Barley developmental mutants tweaky spike (tw) with disturbed auxin pathways possess a unique feature of an increased level of mouldy germinating grains (MGG), which serves as a convenient model to investigate the effects of plant immunity-related substances. The effects of the auxin 2,4-dichlorophenoxyacetic acid (2,4-D), auxin inhibitors, salicylic acid (SA), and trans-cinnamic acid (TCA) were studied using the tw-WT system in surface-sterilized and unsterilized germinating grains under high rates of natural infection. Significant differences among the allelic tw mutants were revealed at the natural MGG level and in response to 2,4-D, SA, and TCA. The most effective means against MGG were sterilization and TCA. 2,4-D inhibited root growth in tw and tw2 mutants, occurring only in unsterilized and not sterilized germinating grains, while the opposite was observed for TCA and SA. The tw mutations influenced variations in the seed-borne fungal spectra, decreasing the frequency of Bipolaris sorokiniana and increasing Fusarium spp. Hypochlorite-based surface sterilization methods should be used with caution in studies where the action of exogenous 2,4-D will be analysed in germinating grains. Auxin pathway disturbances specific for pleiotropic tw mutants are generally restricted to organogenesis but not to germination events.
Highlights
Grain contamination with fungi and their produced mycotoxins is a problem for organic producers and for conventional agriculture [1]
The mouldy germinating grains (MGG) level was significantly lower in surface-sterilized grains than in unsterilized grains under the same experimental conditions, and independent of the plant genotype and the studied 2,4-D concentrations (Figures 1a and 2a, Tables S1a and S2a)
The present study revealed a smaller than expected effect of the exogenous synthetic auxin 2,4-D and both auxin inhibitors hydroxyfluorene-9-carboxylic acid (HFCA) and p-chlorophenoxyisobutyric acid (PCIB) on MGG frequency in tw-type mutants, considering their dramatic rescue effects on variations in spike and floral structure, which were revealed in our previous works [8,9]
Summary
Grain contamination with fungi and their produced mycotoxins is a problem for organic producers and for conventional agriculture [1]. A group of barley pleiotropic tweaky spike (tw)-type mutants (tw, tw , tw2 ) possess a specific tweaked spike structure (Figure S1) and an irregular transformation of lodicules, which are grass-specific floral organs, intoreproductive or chimeric organs. They are characterized by higher susceptibility to Claviceps purpurea and Ustilago nuda, and increased levels of germinating grain moulding [3,4]. The higher susceptibility of tw-type mutants to fungal pathogens may be explained by their polar spike architecture with the semisterile lower part of a spike and overdeveloped multi-rowed upper part, in which flowers with ectopically developed extra floral organs become partially opened during the grain development stage, making it more accessible to external fungal spores and rainwater [3]. The mechanisms leading to MGG of barley tw-type mutants are poorly studied, this phenomenon can still be employed as a convenient and simple model to test the effects of plant immunity-related substances, making barley tw-type mutants a suitable genetic system for an MGG-based assay
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
