Abstract
BackgroundRust diseases are of major importance in wheat production worldwide. With the constant evolution of new rust strains and their adaptation to higher temperatures, consistent and durable disease resistance is a key challenge. Environmental conditions affect resistance gene performance, but the basis for this is poorly understood.ResultsHere we show that a change in day temperature affects wheat resistance to Puccinia striiformis f. sp tritici (Pst), the causal agent of yellow (or stripe) rust. Using adult plants of near-isogenic lines UC1041 +/- Yr36, there was no significant difference between Pst percentage uredia coverage in plants grown at day temperatures of 18°C or 25°C in adult UC1041 + Yr36 plants. However, when plants were transferred to the lower day temperature at the time of Pst inoculation, infection increased up to two fold. Interestingly, this response was independent of Yr36, which has previously been reported as a temperature-responsive resistance gene as Pst development in adult UC1041 -Yr36 plants was similarly affected by the plants experiencing a temperature reduction. In addition, UC1041 -Yr36 plants grown at the lower temperature then transferred to the higher temperature were effectively resistant and a temperature change in either direction was shown to affect Pst development up to 8 days prior to inoculation. Results for seedlings were similar, but more variable compared to adult plants. Enhanced resistance to Pst was observed in seedlings of UC1041 and the cultivar Shamrock when transferred to the higher temperature. Resistance was not affected in seedlings of cultivar Solstice by a temperature change in either direction.ConclusionsYr36 is effective at 18°C, refining the lower range of temperature at which resistance against Pst is conferred compared to previous studies. Results reveal previously uncharacterised defence temperature sensitivity in the UC1041 background which is caused by a change in temperature and independently of Yr36. This novel phenotype is present in some cultivars but absent in others, suggesting that Pst defence may be more stable in some cultivars than others when plants are exposed to varying temperatures.
Highlights
Rust diseases are of major importance in wheat production worldwide
UC1041 -Yr36 plants were less resistant than UC1041 + Yr36, and there were no significant differences in disease levels between plants which were maintained at 12°C/18°C or 12°C/25°C pre and post-inoculation (Figure 1A,B)
The trend in adult UC1041 -Yr36 plants remained consistent in each experiment, with temperature decreases diminishing resistance and temperature increases resulting in enhanced resistance
Summary
Rust diseases are of major importance in wheat production worldwide. Rusts are among the most economically important and widespread diseases of wheat worldwide. Tritici (Pst), is predominantly found in temperate regions and propagates mainly through asexual urediniospores produced in uredia on the leaf surface. Pst urediniospores germinate on the wheat leaf surface, forming a germ tube that enters the plant through stomata. A haustorial mother cell is formed at the end of each infection hypha upon contact with a plant mesophyll cell. An infection peg breaches the plant cell wall forming a fungal feeding structure, known as a haustorium, within the cell. Two weeks after the pathogen has entered the plant, visible symptoms can be seen in susceptible reactions as raised pustules, known as uredia forming on the leaf surface
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