Races Of Crown Rust Research Articles

Preliminary screening of Avena sterilis L. for resistance to crown rust

The best source of crown rust resistance genes (Pc) in genus Avena is a wild hexaploid A. sterilis L. In this study, accessions of A. sterilis gathered from European and North American gene banks, originated from 21 countries were evaluated at the seedling stage for crown rust reaction using the host–pathogen test and two Puccinia coronata f. sp. avenae isolates. Of the 45 oat accessions analyzed, 12 were resistant to one crown rust race (3.2). Resistance to both pathotypes used in the study was observed in two of the accessions, first of which was collected in Libya (AVE 2532) and second in Portugal (CN 26036). Further research is required to evaluate the genetic background of the discovered resistance, however, obtained results provide a valuable first step in the identification of new promising crown rust resistance sources.

Resistance to Puccinia coronata f. sp. avenae in Avena magna, A. murphyi, and A. insularis.

Wild oat tetraploids of the section Pachycarpa have already been proven to be a rich source of useful genes but have largely been unexploited for Puccinia coronata resistance. In this study, accessions of Avena magna, A. murphyi, and A. insularis gathered from European and North American gene banks were evaluated at the seedling stage for crown rust reaction using the host-pathogen test and six highly diverse and virulent P. coronata isolates. Of the 92 Avena accessions analyzed, 58.7% were resistant to at least one crown rust race. In all, 37% of the tested accessions reacted nonuniformly, which indicated their heterogeneity. The highest level of resistance was observed in three of the accessions, one of which was verified by flow cytometry as being hexaploid and two of which were verified as being tetraploids. The infection profiles of 19 accessions corresponded to resistance determined by the genes Pc14, Pc39, Pc40, Pc48, Pc50, Pc54, Pc55, Pc61, Pc67, Pc68, Pc97, Pc101, or Pc104. The patterns of infection of the remaining resistant A. magna and A. murphyi accessions allowed us to postulate the presence of potentially novel crown rust resistance genes.

Are fungicide applications to control crown rust of oat beneficial?

May, W. E., Ames, N., Irvine, R. B., Kutcher, H. R., Lafond, G. P. and Shirtliffe, S. J. 2014. Are fungicide applications to control crown rust of oat beneficial? Can. J. Plant Sci. 94: 911–922. Crown rust (Puccinia coronata Corda f. sp. avenae Eriks.) negatively impacts seed quality and yield in oat (Avena sativa L.) in rust-prone areas of eastern Saskatchewan, Manitoba, Ontario, and Quebec. Genetic resistance is the primary means for controlling this disease, but early seeding and fungicide applications have been suggested to reduce yield losses. Trials were conducted in six locations in Saskatchewan and Manitoba in 2009–2011 to determine the interactions between cultivar, fungicide application, crown rust and seeding date. The cultivars were chosen to represent a range of resistance to the current races of crown rust: AC Morgan, very susceptible; CDC Orrin, susceptible; CDC Boyer, partially resistant; and Leggett, resistant. Crown rust severity varied among locations and cultivars. The sprayed flag and penultimate leaves of AC Morgan tended to have similar amounts of crown rust as the unsprayed leaves of CDC Boyer and CDC Orrin regardless of the level of crown rust infection. Leggett's yield and quality did not respond to fungicide application. Only AC Morgan consistently benefited from a fungicide application. At high crown rust sites fungicide application improved AC Morgan's yield by 17 to 27% (690 kg ha−1 to 781 kg ha−1). Delayed seeding reduced grain yield from 8 to 26% with 8% occurring at low crown rust sites and the largest reductions occurring at high crown rust sites in susceptible cultivars. The test weight of AC Morgan increased from 242 g 0.5 L−1 to 255 g 0.5 L−1 when fungicide was applied at high crown rust sites seeded in mid-May. Fungicide application did not change the test weight of Leggett. The β-glucan level was affected more by seeding date (0.4%) and cultivar (0.4%) than fungicide application (0.1%). Seeding a cultivar with better crown rust resistance than AC Morgan in mid-May eliminated most of the benefits derived from fungicide application. These results indicate that prophylactic fungicide applications are unlikely to provide yield improvement when early planting is combined with even a moderately disease-resistant cultivar.

Lee Williams hulless oat

Lee Williams is a high-yielding hulless oat (Avena sativa L.) with good disease resistance and good straw strength. It is well adapted to all of the oat producing regions of western Canada. It carries genetic resistance to several races of crown rust (caused by Puccinia coronata Corda f. sp. avenea Eriks.) and stem rust (caused by P. graminis f. sp. avenae Pers.), loose [Ustilago avenae (Pers.) Rostr.], and covered smut (U. kolleri Wille), and moderate resistance to barley yellow dwarf virus (BYDV). Lee Williams has protein and oil levels and a high groat to hull ratio that make it well-suited for livestock feed. Hulless oat may retain a low percentage of hulls after threshing so a high groat to hull ratio is desirable. Lee Williams was supported for registration at the Prairie Regional Recommending Committee for Grains meeting in February 2002.Key words: Oat, Avena sativa L., cultivar description, hulless oat

Broad-Spectrum Resistance to Crown Rust, Puccinia coronata f. sp. avenae, in Accessions of the Tetraploid Slender Oat, Avena barbata.

The use of race-specific seedling genes for resistance has been the primary means of controlling crown rust of oat (Puccinia coronata). As resistance genes from hexaploid cultivated oat, Avena sativa and, later, the wild hexaploid animated oat, A. sterilis, were deployed in oat cultivars, corresponding virulence in the crown rust population increased rapidly, such that the effective lifespan of a resistant cultivar in the United States is now 5 years or less. Introgression of resistance genes from diploid and tetraploid Avena spp. into hexaploid oat has been difficult due to differences in ploidy levels and the lack of homology of chromosomes between the two species. The wild tetraploid slender oat, A. barbata, has been a source of powdery mildew and stem rust resistance in cultivated oat but has largely been unexploited for crown rust resistance. In total, 359 accessions of A. barbata from the National Small Grains Collection were evaluated in seedling greenhouse tests. Of these accessions, 39% were at least moderately resistant when inoculated with a crown rust race with low virulence (DBBC). When tested further with a highly diverse bulk inoculum from the 2006 and 2007 St. Paul buckthorn nursery, 48 accessions (approximately 13%) were resistant. Many of these accessions were heterogeneous in reaction, but two accessions (PI320588 from Israel and PI337893 from Italy) were highly resistant (immune) and two others (PI337886 from Italy and PI367293 from Spain) consistently produced resistant reactions (chlorotic flecks) in all tests. Resistant accessions were found from throughout much of the natural range of A. barbata. Crosses of some of the better accessions have been made to cultivated oat.

Restriction fragment length polymorphisms linked to genes for resistance to crown rust (Puccinia coronata) in near-isogenic lines of hexaploid oat (Avena sativa)

Crown rust, perhaps the most important fungal disease of oat, is caused by Puccinia coronata. An examination of near-isogenic lines (NILs) of hexaploid oat (Avena sativa) was conducted to identify markers linked to genes for resistance to crown rust. These lines were created such that a unique resistance gene is present in each of the two recurrent parent backgrounds. The six NILs of the current study, X434-II, X466-I, and Y345 (recurrent parent C237-89) and D486, D494, and D526 (recurrent parent Lang), thus provide a pair of lines to study each of three resistance genes. Restriction fragment length polymorphisms and resistance loci were mapped using BC1F2 populations. Three markers were found linked to a locus for resistance to crown rust race 203, the closest at 1.9 cM in line D494 and 3.8 cM in line X466-I. In lines D526 and Y345 a marker was placed 1.0 and 1.9 cM, respectively, from the locus conferring resistance to crown rust race 345, and in D486 and X434-II a marker mapped at 8.0 and 10.2 cM from the locus for resistance to rust race 264B.

Linkage of genes conferring specific resistance to oat crown rust in diploid Avena

The inheritance of resistance to an isolate of crown rust race 276 was investigated in four diploid oat lines. F3 families derived from Avena strigosa C.I. 2630 x Avena nuda C.I. 9009, Avena wiestii C.I. 1994 x Avena strigosa C.I. 3815, and C.I. 3815 x C.I. 2630 were inoculated at the seedling stage and evaluated 9-12 days later. Segregation of the F3 families indicated that C.I. 2630 and C.I. 3815 each possess one dominant gene that conditions resistance to race 276. The alleles conferring resistance occur at two different loci, separated by 17 cM on the same chromosome, and appear to be complementary. C.I. 3815 may have an additional recessive resistance allele at a different locus on the same chromosome, 19 cM from its other resistance gene locus.

AC Stewart oat

AC Stewart oat (Avena sativa L.) is a spring-type cultivar suitable for the feed, food (milling) and mixed grain (oat and barley) industries in Ontario. This variety combines high grain yield, large kernel size, early maturity and strong straw with disease resistance required for production in Ontario. AC Stewart is very similar in plant type and barley yellow dwarf resistance to its recurrent parent Ogle and, in addition, possesses genes conferring resistance to loose smut (Ustilago avenae (Pers.) Rostr.) and to prevalent races of crown rust (Puccinia coronata Pers. f. sp. avenae Eriks. and E. Henn.) and some prevalent races of stem rust (Puccinia graminis Pers. f. sp. avenae Eriks. and E. Henn.) in Ontario.Key words: Avena sativa L., rust, smut and BYDV resistance, cultivar description, oat

NEWMAN OAT

Newman oat (Avena sativa L.) is a daylength insensitive, spring-type cultivar suitable for the feed, food (milling) and mixed grain (oat and barley) industry in Ontario. Newman is very similar to its recurrent parent Donald and in addition, it possesses genes conferring resistance to prevalent races of crown rust and some prevalent races of stem rust.Key words: Avena sativa L., daylength insensitive, rust and smut resistance, cultivar description, oat

TIBOR OAT

Tibor is a new naked-seeded or hulless oat cultivar (Avena nuda L.) suitable for growing in eastern Canada. Compared with the naked-seeded check cultivar Terra, Tibor is higher in groat yield, seed and hectolitre weight and seed protein content. It has excellent straw strength coupled with tall plant height and early maturity, but shows no improvement over Terra in the percentage of covered seeds (approximately 5%) in threshed grain samples or in resistance to diseases such as barley yellow dwarf virus, septoria or stem rust. Tibor is susceptible to prevalent races of crown rust but the disease is slow to develop in field-scale plantings. Tibor is resistant to loose smut and Victoria blight.Key words: Avena nuda L., cultivar description, oat (hulless)

Effects of elevated temperature and α-aminooxyacetate on the accumulation of avenalumins in oat leaves infected with Puccinia coronata f. sp. avenae

The rapid accumulation of avenalumins in incompatible crown rust-infected Shokan 1 oat leaves which occurred at 20 °C was greatly inhibited when infected plants were grown at 25 to 35 °C. At 30 °C, avenalumin accumulation was almost totally inhibited and much greater hyphal growth occurred than at 20 °C. When infected plants were grown at 20 °C for 36 h and then transferred to 30 °C, most of the previously-accumulated avenalumins disappeared rapidly within 48 h and hyphal growth continued. However, no subsequent hyphal growth resulted when the plants were transferred to 30 °C at 72 h after inoculation. Treatment of plants with α-aminooxyacetate, a potent competitive inhibitor of phenylalanine ammonia-lyase, greatly inhibited the rapid accumulation of avenalumins in normally incompatible interactions. This was correlated with an increase in susceptibility of the host plants. Significant inhibition of avenalumin accumulation was observed 48 h after inoculation when inoculation was followed by application of the inhibitor at 10 μ m, but much less inhibition of hypersensitive host cell collapse occurred in the treated leaves. These facts suggest that rapid and large accumulation of the avenalumins is crucial for resistance expression in oat leaves against an incompatible crown rust race.

Comparison of Different Hill‐plot Designs for Evaluating Quantitative Response to Oat Crown Rust1

Four hill‐plot field designs and a rod‐row design (plan 5) were compared for evaluation of the quantitative responses of five oat (Avena sativa L.) cultivars to two races of crown rust (Puccinia coronata Cda.) each at two levels of infection. In hill‐plot plan 1, test hills were planted in rows in a solid block. In plan 2, test hills were planted in rows alternating with rows of susceptible rust‐spreader hills. In plan 3, test hills were surrounded by barley (Hordeum vulgare L.) hills. In plan 4, single oat plants were grown in barley hills.Evaluation of response to rust was based on how the performance of rusted plots compared with the performance of corresponding unrusted control plots. Rust severity was highest in plan 1; intermediate in plans 2, 3, and 5; lowest in plan 4. A combined analysis of data from plans 1, 2, and 3 showed that cultivars, plans, rows, and levels of infection all significantly affected both yield and seed weight in terms of reduction due to rust infection. The plan ✕ cultivar interaction was significant for reduction in seed weight, but not for reduction in yield. However, in the four hill‐plot plans and the rod‐row plots, the cultivars ranked the same in order of reduction in seed weight. All correlation coefficients among the different plans for yield and seedweight reductions were significant. Coefficients of variation for these traits were lowest for the rod‐row plots; intermediate for plans 1, 2, and 3; and highest for plan 4. Plan 1 was most desirable for general use.

Oat crown rust race differentiation: replacement of the standard differential varieties with a new set of single resistance gene lines derived from Avena sterilis

A review of the physiologic races of oat crown rust, Puccinia coronata f. sp. avenae, isolated in surveys since 1967 indicated a continuing trend toward increased virulence on the standard differential varieties of oats, Avena sativa. Because of this trend and because the inheritance and interrelationships of resistances in the standard differential set are not completely known, a new set of oat crown rust differentials has been introduced. The new set comprises 10 near-isogenic lines of the common oat variety 'Pendek,' into which single resistance genes from Avena sterilis had been transferred. A system of race nomenclature which reflects the pattern of virulence on the new set is proposed.

Relative Tolerance of Contemporary Oat Cultivars to Currently Prevalent Races of Crown Rust1

We tested about 100 contemporary oat (Avena sativa L.) cultivars, all visually rated as susceptible to crown rust (Puccinia coronata Cda. var. avenae Fraser and Led.) race 326, with severe field epiphytotics of this race. Eleven eultivars were then selected for more intensive testing with races 216 and 264, as well as with race 326. Yield and seed weight data showed that some cultivars (‘Clintland 64,’ ‘Jaycee,’ ‘Tippecanoe,’ and ‘Tyler’) were damaged as severely by race 326 as was the old highly susceptible ‘Clinton,’ while others (‘Kota,’ ‘Nodaway,’ and ‘Nodaway 70’) yielded almost as much as the resistant check.

Absence of lateral transfer within the oat leaf of substances responsible for crown rust resistance

The longitudinal half of each of three inoculated leaves of an unusual trisomic oat seedling was resistant and the other half susceptible to crown rust race 264. Resistance was conditioned by the Pc-15 gene located on the extra M4 chromosome. It is postulated that the chimera resulted early in the ontogeny of the plant and one of the cells which eventually developed into the susceptible half of the plant failed to receive or lost its M4 chromosome. The chimera demonstrates that the factors responsible for crown rust resistance are not mobile, in a lateral direction, within the leaf.

Inheritance of Crown Rust Resistance in Avena Sterilis1

The inheritance of resistance in three collections of Avena sterilis (F83 and F366 from Israel, and CW491‐4 from Algeria) to races 264, 290, 295, 332, and 446 of crown rust, Puccinia coronata avenae, was investigated. Genetic analysis indicated that two of the collections (CW491‐4 and F366) each had a single gene (Pc‐38 and Pc‐39 respectively), independent of each other, which conditioned resistance to these five races of crown rust and to every other isolate to which they were tested.Four distinct genes for crown rust resistance were discovered in the third A. sterilis collection, F83. Gene Pc‐40 was epistatic to the other three genes in F83, and conditioned resistance to races 290, 295, 332, and 446, but not to race 264. Gene Pc‐41 conferred resistance to races 290, 295, and 332, while gene Pc‐42 was effective only against race 332 and gene Pc‐43 only against race 290. Some backcross families of F83 that were susceptible to all five of these races segregated for resistance to a few of the other crown rust races against which they were tested, indicating the presence of an additional gene. Genes Pc‐38, Pc‐39, Pc‐40, and Pc‐42 all conditioned fleck type resistance. Gene Pc‐41 conditioned intermediate type 2 resistance, while gene Pc‐43 was incompletely dominant and conditioned either fleck or type 2 resistance.

VIRULENCE OF UREDIAL AND AECIAL ISOLATES OF PUCCINIA CORONATA CORDA F.SP. AVENAE IDENTIFIED IN CANADA FROM 1952 TO 1966

Isolates of Puccinia coronata f.sp. avenae collected during a 15-year period were tested for virulence on the crown rust differential oat varieties. The proportion of cultures virulent on Landhafer increased relative to others during this period, and was related to the release in the United States of commercial varieties that contained this type of resistance. These varieties served to reduce the proportion of races avirulent on Landhafer in the crown rust population that reached Canada.The occurrence and subsequent increase in frequency of isolates virulent on Victoria was correlated with the release of the oat varieties Rodney and Garry which possess part of the crown rust resistance of Victoria. The increased proportion of cultures that attacked Ukraine also paralleled the release of these two commercial varieties. This suggests that Ukraine either contains the Victoria Pc-11 gene for crown rust resistance that was transferred to Rodney and Garry, or that it contains another gene in common with these varieties.Races of crown rust that are differentially virulent on the varieties Landhafer and Santa Fe have recently been found in Canada. One culture was virulent on the variety Bondvic but not on Trispernia. No increase in race 264 of crown rust, which attacks all the differential sources of resistance except Saia, has been observed since it was first identified in Canada in 1957.Presentation of the virulence of crown rust isolates for individual types of resistance was found to express the results of race surveys in terms which were more meaningful to the oat breeding program. This form of analysis also produced valuable information on the possible relationships of genes for resistance in different oat varieties not readily obtainable from conventional information on the occurrence and distribution of physiologic races of crown rust.

PHYSIOLOGIC RACES OF OAT CROWN RUST ISOLATED FROM AECIA ON BUCKTHORN AND THEIR RELATION TO THE RACIAL POPULATION ON OATS IN SOUTHEASTERN ONTARIO AND MANITOBA

The physiologic race composition of isolates of oat crown rust, Puccinia coronata Corda f. sp. avenae Erikss., from aecia on buckthorn, Rhamnus cathartica L., was correlated with the races isolated from oats, Avena saliva L., in southwestern Ontario and Manitoba respectively. Among the races isolated from aecia in each region, predominant were virulent races which were isolated also from infected oats growing in the buckthorn areas. This suggests strongly that the alternate host is important in initiating crown rust epiphytotics.Races virulent on Landhafer and Santa Fe oats comprised 52% of the isolates from oats and 45% of the isolates from buckthorn in Manitoba. Isolates from oats and buckthorn in Ontario were also correlated, with the most prevalent races being those virulent on Victoria and Bond. They comprised 55% and 45% of the isolates from the principal and alternate hosts respectively.Eight races of crown rust recently discovered in Canada are described in terms of their reactions on the standard set of differential varieties. It is suggested that hybridization on the alternate host would adequately account for the origin of these new races.

REACTION OF NON-CULTIVATED OATS FROM ISRAEL TO CANADIAN RACES OF CROWN RUST AND STEM RUST

Two hundred and two collections of non-cultivated oats from Israel, belonging to Avena sterilis L. and A. barbata Brot., were tested in the greenhouse at Winnipeg, Manitoba, for seedling and adult plant reaction to several important crown rust and stem rust races. Seeds of the collections found resistant in the greenhouse to one of the test races were planted in the field and were exposed to artificial rust epidemics. Out of 123 collections of A. sterilis, 40 were resistant to crown rust in the greenhouse and 9 remained resistant in the field; one collection was resistant to stem rust in the greenhouse but none was resistant in the field. Out of 79 collections of A. barbata, 23 were resistant to crown rust in the greenhouse and 8 maintained resistance in the field; 17 collections were resistant to stem rust in the greenhouse and 8 were resistant in the field.Crown rust and stem rust resistance factors seem to be independent of each other; the plants of only a few collections possessed resistance to both rusts. Collection D203 was particularly outstanding, showing resistance to all the test races of crown rust and stem rust in seedling and adult stages in the greenhouse as well as in the field.

THE DISTRIBUTION AND FREQUENCY OF OCCURRENCE OF PHYSIOLOGIC RACES OF PUCCINIA CORONATA CORDA F. SP. AVENAE ERIKSS., IN CANADA, 1952 TO 1961

From 1952 to 1956 the races of crown rust, Puccinia coronata Corda f. sp. avenae Erikss., that predominated in Eastern Canada were 201, 202, 203, 209, 239, and 240. Races 201, 202, and 204 occurred most frequently in Western Canada. These races cannot attack the differential host variety Victoria, from which the currently grown commercial varieties Rodney and Garry derive their resistance. Garry and Rodney became widely grown in Canada by 1957, and since then races 216 and 274, which can attack Victoria, have become prominent, especially in Western Canada.More races are found in Eastern Canada than in the west, and there is less tendency for a few races to predominate in the east. These differences may be explained by the relatively frequent occurrence of the alternate host, Rhamnus cathartica L., in important oat-growing regions of Eastern Canada, and by the cultivation of large acreages of a few varieties with similar resistance in the west. The most important factor affecting the distribution and frequency of occurrence of races is the variety grown.