Potential for re-emergence of wheat stem rust in the United Kingdom

This is the final version. Available on open access from Springer Nature via the DOI in this recordWheat stem rust, a devastating disease of wheat and barley caused by the fungal pathogen Puccinia graminis f. sp. tritici, was largely eradicated in Western Europe during the mid-to-late twentieth century. However, isolated outbreaks have occurred in recent years. Here we investigate whether a lack of resistance in modern European varieties, increased presence of its alternate host barberry and changes in climatic conditions could be facilitating its resurgence. We report the first wheat stem rust occurrence in the United Kingdom in nearly 60 years, with only 20% of UK wheat varieties resistant to this strain. Climate changes over the past 25 years also suggest increasingly conducive conditions for infection. Furthermore, we document the first occurrence in decades of P. graminis on barberry in the UK . Our data illustrate that wheat stem rust does occur in the UK and, when climatic conditions are conducive, could severely harm wheat and barley production.This project was funded by an institute development grant from the EI (Norwich, UK), an Industrial Partnership Award (BB/M025519/1) from the BBSRC, a European Research Council Starting Grant awarded to D.G.O.S. (number 715638), H2020 project EMPHASIS (number 634179), by the BBSRC Institute Strategic Programmes BB/J004553/1 and BB/P012574/1, the John Innes Foundation, and an African Women in Agricultural Research and Development (AWARD) fellowship to R.N.K

The wheat stem rust resistance gene Sr43 encodes an unusual protein kinase

To safeguard bread wheat against pests and diseases, breeders have introduced over 200 resistance genes into its genome, thus nearly doubling the number of designated resistance genes in the wheat gene pool1. Isolating these genes facilitates their fast-tracking in breeding programs and incorporation into polygene stacks for more durable resistance. We cloned the stem rust resistance gene Sr43, which was crossed into bread wheat from the wild grass Thinopyrum elongatum2,3. Sr43 encodes an active protein kinase fused to two domains of unknown function. The gene, which is unique to the Triticeae, appears to have arisen through a gene fusion event 6.7 to 11.6 million years ago. Transgenic expression of Sr43 in wheat conferred high levels of resistance to a wide range of isolates of the pathogen causing stem rust, highlighting the potential value of Sr43 in resistance breeding and engineering

Potential for re-emergence of wheat stem rust in the United Kingdom

Wheat stem rust, a devastating disease of wheat and barley caused by the fungal pathogen Puccinia graminis f. sp. tritici, was largely eradicated in Western Europe during the mid-to-late twentieth century. However, isolated outbreaks have occurred in recent years. Here we investigate whether a lack of resistance in modern European varieties, increased presence of its alternate host barberry and changes in climatic conditions could be facilitating its resurgence. We report the first wheat stem rust occurrence in the United Kingdom in nearly 60 years, with only 20% of UK wheat varieties resistant to this strain. Climate changes over the past 25 years also suggest increasingly conducive conditions for infection. Furthermore, we document the first occurrence in decades of P. graminis on barberry in the UK. Our data illustrate that wheat stem rust does occur in the UK and, when climatic conditions are conducive, could severely harm wheat and barley production.</p

Determination of tannin levels in multi-purpose Kenyan trees and fodder crops, their variation and effect on protein digestibility in ruminants

Energy and protein are the major limiting nutrients in dairy production on the small scale mixed farms in Kenya. Commercial feed supplements are expensive and therefore multipurpose fodder trees (MPT) and forage crops are advocated as the alternative supplements, because they are inexpensive, able to provide green forage even in dry season and have high protein content. These trees have tannins whose levels, seasonal and altitude distribution have not been established. Previous studies have indicated that tannins may have either beneficial effects like bloat control and increased protein bypass, or deleterious effects like the reduction feed intake and digestibility of protein in animals fed on tanniferous feed. The objectives of this study were to determine the tannin levels in the MPT, as influenced by altitude and season, and the effect of these tannins on ruminal degradation and intestinal digestion of the diet. Samples of four multipurpose fodder trees and four forage crops viz. leucaena, sesbania, gliricidia, calliandra, velvet bean, green leaf and silver leaf desmodium and cassava, were collected at Mombasa (low altitude, below 300 m ASL.) in the wet season and at Embu (high altitude, 1500 m ASL.) in both wet and dry season. Tannin and protein content were determined using gravimetric and wet oxidation nitrogen determination methods respectively. The effect of tannin on protein degradability was determined by comparing the polyethylene glycol (PEG) treated with untreated forage samples using the mobile nylon bag technique. The treated and untreated samples were incubated separately in the rumen of four Holstein cows with both rumen and duodenal cannula for 0, 6, 12, 24, 48 and 96 hours. Afterwards two sample of each species from time 12 and 24 hours were inserted into the intestine through duodenal cannula, and recovered from the feces. The dry matter (DM) and protein of samples recovered from the rumen and feces were determined and these values were fitted in anon linear regression equation P = a + b(1— ") The results indicated that the MPT had ytterbium-precipitatable tannins ranging from 16.08 (±2.39)% of the DM in Gliricidia sepium to 30.31 (±2.42)% in Desmodium. intortum. The tannin content varied significantly (P<0.05) with species. The altitude did not have significant effect on tannin content, but tannins within species behaved differently with season. The protein content differed significantly (P<0.05) with species. Proteins were significantly (P<0.05) higher in wet than in theory season. The altitude had no effect on protein content. The tannin : protein ratio also varied significantly (P<0.05) with species. Species also had a significant interaction with season. Tannins significantly (P<0.05) reduced the rumen effective degradability of both DM and crude protein in all species, resulting in large quantities of undegraded dietary nitrogen(N). Tannin also significantly (P<0.05) decreased the total tract digestion of the DM (DMD) and depressed the digestible crude protein (DCP) of leucaena, calliandra, cassava and aintortum, but had no effect on gliricidia, sesbania and velvet bean DCP. A large proportion of the rumen undegraded dietary protein that reached the intestines was degraded in most species except calliandra. Tannin significantly (P<0.05) altered the degradability constants a, b, and c for both DM and CP by reducing fraction a and the rate of degradation c and increasing the b fraction. From the study it was concluded that the MPT and forage crop species, despite their high protein content, are not good protein supplements. Their tannins reduce both the CP digestibility and the DM degradability in the rumen. Lastly, potentially viable treatments that reduce the effect of tannin on digestibility are suggested.Land and Food Systems, Faculty ofGraduat

Potential for re-emergence of wheat stem rust in the United Kingdom.

Wheat stem rust, a devastating disease of wheat and barley caused by the fungal pathogenPuccinia graminis f. sp. tritici, was largely eradicated in Western Europe during the mid-to-latetwentieth century. However, isolated outbreaks have occurred in recent years. Here weinvestigate whether a lack of resistance in modern European varieties, increased presence of itsalternate host barberry and changes in climatic conditions could be facilitating its resurgence.We report the first wheat stem rust occurrence in the United Kingdom in nearly 60 years,with only 20% of UK wheat varieties resistant to this strain. Climate changes over the past 25years also suggest increasingly conducive conditions for infection. Furthermore, we documentthe first occurrence in decades of P. graminis on barberry in the UK . Our data illustrate thatwheat stem rust does occur in the UK and, when climatic conditions are conducive, couldseverely harm wheat and barley production

Population genomic analysis of Aegilops tauschii identifies targets for bread wheat improvement.

Aegilops tauschii, the diploid wild progenitor of the D subgenome of bread wheat, is a reservoir of genetic diversity for improving bread wheat performance and environmental resilience. Here we sequenced 242 Ae. tauschii accessions and compared them to the wheat D subgenome to characterize genomic diversity. We found that a rare lineage of Ae. tauschii geographically restricted to present-day Georgia contributed to the wheat D subgenome in the independent hybridizations that gave rise to modern bread wheat. Through k-mer-based association mapping, we identified discrete genomic regions with candidate genes for disease and pest resistance and demonstrated their functional transfer into wheat by transgenesis and wide crossing, including the generation of a library of hexaploids incorporating diverse Ae. tauschii genomes. Exploiting the genomic diversity of the Ae. tauschii ancestral diploid genome permits rapid trait discovery and functional genetic validation in a hexaploid background amenable to breeding

Population genomic analysis of Aegilops tauschii identifies targets for bread wheat improvement

Aegilops tauschii, the diploid wild progenitor of the D subgenome of bread wheat, is a reservoir of genetic diversity for improving bread wheat performance and environmental resilience. Here we sequenced 242 Ae. tauschii accessions and compared them to the wheat D subgenome to characterize genomic diversity. We found that a rare lineage of Ae. tauschii geographically restricted to present-day Georgia contributed to the wheat D subgenome in the independent hybridizations that gave rise to modern bread wheat. Through k-mer-based association mapping, we identified discrete genomic regions with candidate genes for disease and pest resistance and demonstrated their functional transfer into wheat by transgenesis and wide crossing, including the generation of a library of hexaploids incorporating diverse Ae. tauschii genomes. Exploiting the genomic diversity of the Ae. tauschii ancestral diploid genome permits rapid trait discovery and functional genetic validation in a hexaploid background amenable to breeding