Genetics of resistance to Puccinia graminis tritici and Puccinia recondita tritici in Kenya Plume wheat

Summary Seven genes, viz. Sr5, Sr6, Sr7a, Sr8a, Sr9b, Sr12 and Sr17 were associated with seedling resistance to Puccinia graminis tritici in Kenya Plume wheat. The predominant field cultures were avirulent on seedlings with Sr7a, but possessed virulence for the other six genes. However, Sr7a did not confer adult-plant resistance when present on its own. Adult-plant resistance was attributed to Sr2 and possibly also to the interaction of Sr7a and Sr12.Two genes, Lr13 and Lr14a, were identified in seedling tests with various cultures of Puccinia recondita tritici. Lr13 conferred adult-plant resistance to the predominant field strains. Genetic recombination between Lr13 and Sr9b was estimated at 17.6±3.1%.     

Reactions of Hordeum spontaneum to infection with two cultures of Puccinia hordei from Israel and United States

Summary The reactions to infection with two cultures of Puccinia hordei were determined for 292 Hordeum spontaneum (syn. H. vulgare ssp. spontaneum) accessions, collected at 16 sites which encompassed the ecological range of H. spontaneum in Israel. Culture Tel-Aviv was from Israel and culture 57.19 was from the United States. Fifty-two percent of the accessions were resistant to culture Tel-Aviv and 67% were resistant to culture 57.19. Forty-three percent of the accessions were resistant to both cultures. The average infection type (IT) of accessions within sites ranged from 2.7 to 7.5 on a 0–9 rating scale. The results showed that the presence of Ornithogalum species, the alternate hosts of P. hordei, may increase the percentage of H. spontaneoum accessions resistant to P. hordei. More accessions were resistant at sites where humidity at 1400 was higher, the annual evaporation was lower, and where the glumes were shorter. Kernel weight and annual rainfall was not correlated with resistance. A lower percentage of H. spontaneum accessions were resistant to P. hordei culture Tel-Aviv from Israel than to culture 57.19 from the United States. In a previous study a lower percentage of H. spontaneum accessions also was found to be resistant to a culture of Erysiphe graminis hordei from Israel than to cultures from other countries. Previous studies also have shown that cultures of P. hordei and E. graminis hordei from Israel have many genes for virulence on barley, and that H. spontaneum accessions from Israel have many genes for resistance to these two pathogens. Previous results and the results reported in this paper support the hypothesis of coevolution of resistant host genes and virulent pathogen genes where hosts and pathogens have coexisted for many thousand years.     

Regional phenotypic diversity of Puccinia triticina and wheat host resistance in western Europe, 1995

Pathogenicity data from surveys of Puccinia triticina (formerly P. recondita f. sp. tritici) conducted in western Europe in 1995 were analysed to compare the structure of regional populations of the pathogen. Many of the populations differed in phenotypic diversity and pathotypic composition, even though they occurred within a single epidemiological unit, suggesting that local factors may influence the establishment and propagation of individual pathotypes in the regional populations. Neighbouring regions were more similar than distant regions, and all regions shared at least one pathotype, except populations in northern Italy and Scotland. A high degree of similarity was found between populations in northern France and Great Britain, providing strong evidence of free movement of inoculum between these regions. Resistance genes were postulated for a selection of 91 wheat cultivars, representing those most commonly grown in western Europe in 1995. Thirteen cultivars lacked detectable seedling resistance genes and the remaining 78 possessed from one to three resistance genes; those detected were Lr1, Lr3a, Lr10, Lr13, Lr14a, Lr17b, Lr20, Lr26 and Lr37. The most commonly detected resistance gene was Lr13, which was present singly or in combination with other resistance genes in 48 cultivars (53%). The gene Lr14a was detected in 18 cultivars, Lr26 was present in 16 cultivars. The role of host selection in the composition of the regional populations of P. triticina in western Europe in 1995 was difficult to assess on the basis of the results obtained, since virulence data were not available for Lr13 and Lr14a. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetics of resistance to Puccinia recondita in two wheat crosses

Leaf rust resistance genes were identified in the common wheat variety ‘HUW 206’ and line HUWL 39 by inoculating their seedlings with 20 pathotypes of diverse avirulence–virulence combinations. The inheritance patterns and allelic relationships were studied by crossing these wheats with ‘Agra Local1 and a set of Thacher’ near-isogenic lines with genes for resistance. Seedling resistance studies revealed the presence of genes Lr1, Lr10 and Lr26 in ‘HUW 206’ and genes Lr10 and Lr26 in HUWL 39. The presence of genes Lr1 and Lr10 was confirmed indirectly by testing for the linked genes Sr31 and Yr9. An F₁ test for progressive necrosis in crosses of the lines with ‘Spica’ revealed the absence of Lr13.     

Resistance in three common wheat cultivars to Puccinia graminis

Summary The genetic basis of resistance in three wheat cultivars to cultures of P. graminis tritici of unusua avirulence, P. graminis secalis, and sexual or somatic hybrids between these formae speciales was investigated. Eight genes conditioning resistance were found. Federation and Morocco each possessed three, and Purple Straw had two genes.Genes Sr18, SrFr2 and SrMrc3 for resistance to hybrid rusts and found in Purple Straw, Federation and Morocco respectively, were ineffective against the cultures of P. graminis tritici and P. graminis secalis used.     

Inheritance and characterization of the new and rare gene Rph25 conferring seedling resistance in Hordeum vulgare against Puccinia hordei

In this study, we characterized and mapped a new and rare resistance gene (RphFT) in the Chinese barley variety ‘Fong Tien’. RphFT, a dominant gene, was mapped to chromosome 5HL at a genetic position of 142.1 cM using DArT‐seq markers. The gene was also confirmed to be present in Australian cultivar ‘Yagan’ based on allelic tests, and likely ‘Lockyer’ based on multipathotype tests. The genetic studies also confirmed the presence of Rph12 in Australian cultivar ‘Baudin’. Rph12 is also located on chromosome 5HL close to RphFT, and the two loci were confirmed to be independent. Gene RphFT is of limited breeding value because it is effective to only one pathotype of P. hordei, 220P+ +Rph13 in Australia; nevertheless, it may play a role in controlling leaf rust if used in combination with other Rph genes. The locus symbol Rph25 is recommended for RphFT in accordance with the rules and numbering system of barley gene nomenclature.     

A new virulent strain of Puccinia hordei

Summary Four cultures of Puccinia hordei isolated from the alternate Ornithogalum hosts in Israel were virulent on seedlings of barley cultivars carrying resistance genes Pa, Pa2, Pa2 + Pa5, Pa2 + Pa6, Pa3, Pa4, and Pa7. Cultures with such a spectrum of virulence have never been reported. The cultures remained stable through 20 successive inoculation and isolation cycles. One of the cultures, T-40SS, retained its specific virulence after selfing on the alternate host. The evolution of virulent races of obligate parasites in the centers of origin of their hosts is discussed.     

Temperature-sensitive genes for resistance to Puccinia striiformis in Triticum dicoccoides

Summary Twenty-six selections of wild emmer collected at different sites in Israel and three entries obtained from Turkey were studied for the possible presence of temperature-sensitive genes controlling reaction to Puccinia striiformis. In tests carried out in Israel with a local P. striiformis isolate at two temperature regimes, 16 selections showed a change in infection rating toward resistance at the higher temperature regime. In comparable tests performed in the United States with a Montana P. striiformis isolate of different virulence pattern-including 14 of the same selection—ten entries displayed a temperature-sensitive reaction. Although slightly different temperature regimes were used in Israel and the United States, the results obtained were in general agreement. The shift toward resistance observed in the seedling tests at the higher temperature-profile was also evident in the field in the mature plant stage with increasing spring temperatures.     

Sources of resistance to Indian pathotypes of Puccinia graminis tritici and P. triticina in durum wheat

Stem rust and leaf rust are important diseases affecting durum wheat production in India. Inheritance and extent of diversity in resistance were studied in five durum genotypes, viz. ?B 662', ?ED 2398‐A', ?HG 110', ?IWP 5019' and ?Line 1172? using Pgt pathotypes 40A and 117‐6, and Pt pathotypes 12‐2 and 104‐2. F₂ and F₃ analyses showed that resistance was conferred by one or two genes in each line. In all, four genes for resistance to 40A, and eight each for pathotypes 117‐6 and 12‐2 were identified among the five genotypes, and three for resistance to 104‐2 among B 662, ED 2398‐A and IWP 5019 were indicated by tests of allelism. Although the gene identities are not known, at least some of them should be different from Sr2, Sr7b, Sr8a, Sr8b, Sr9e, Sr9g, Sr11, Sr12, Sr13, Sr14, Sr17, Sr23 and Sr28; and from Lr3, Lr14a, Lr23 and Lr27 + Lr31. These genotypes enrich the diversity of resistance to stem rust and leaf rust for durum wheat improvement.     

Isozyme variation in cultivated and wild pineapple

Summary Isozyme variation was studied in 161 accessions of pineapple including four species of Ananas and one of Pseudananas. Six enzyme systems (ADH, GPI, PGM, SKDH, TPI, UGPP) involving seven putative loci revealed 35 electromorphs. Considerable variation exists within and between species of Ananas. Sixty-six distinct zymotypes were identified. Multivariate analyses of isozyme variation indicated that A. comosus contains five genetically diverse groups that do not match perfectly with the traditional varietal groups. Isozyme evidence also suggests that A. erectifolius is a conspecific variant of A. comosus, and that among other wild species, A. ananassoides is more closely related to A. comosus than A. bracteatus. Pseudananas is genetically distinct from all species of Ananas. It is evident from our study that differentiation among the species of Ananas may be due to ecological isolation rather than genetic divergence with breeding barriers and therefore may represent a species complex.This is journal series No. 3956 of the Hawaii Institute of Tropical Agriculture and Human Resources.     

Inheritance of resistance to Puccinia coronata var. avenae in six selections of Avena sterilis

Summary Six selections of Avena sterilis, introduced from Israel as sources of resistance to oat crown rust, were crossed with susceptible A. byzantina Frazier. The number of genes conditioning resistance to culture H-14 of race 326 of Puccinia coronata var. avenae in each of the six selections was determined from studies of F₁, F₂ and F₃ populations from the crosses. P.I. 287211, P.I. 295919 and P.I. 296244 each appeared to have a single dominant gene for resistance, and P.I. 296265 and P.I. 296266 each two dominant ones. C.I. 8295 had a single partially dominant gene for resistance. Crosses among the A. sterilis parents indicated that at least four different genes conditioned resistance to culture H-14.Association between F₂ reaction to crown rust and morphological characters of the spikelet was determined with the % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiabeE8aJnaaCa% aaleqabaGaaGOmaaaaaaa!39FC!\[\chi ^2 \] test for independence. In four crosses, all spikelet characters appeared to be independent of rust reaction. In Frazier x P.I. 296244, basal pubescence of the lemma on the secondary floret appeared to be associated with reaction to crown rust. Strong association between reaction to crown rust and lemma pubescence on the primary floret was evident in Frazier x P.I. 296265.     

Variation in the grass pea (Lathyrus sativus L.) and wild species

Summary Forty-nine accessions of Lathyrus sativus were studied for morphological variation. Data were analysed using Principal Components Analysis and Cluster Analysis. The variation in 14 species of Section Lathyrus was also evaluated in order to ascertain affinities between L. sativus and other species. L. sativus is a highly variable species, and there is a clear distinction between the blue-flowered forms from south-west Asia, Ethiopia and the Indian subcontinent, and the white and white and blue flowered forms with white seeds which have a more westerly distribution. Differences in vegetative parts may be due to selection for forage types. L. sativus appears to be closely related to L. cicera and L. gorgoni, and this relationship needs further investigation.     

Somatic chromosomes of some Coffea species

Twenty-two somatic chromosomes have been found in six Coffea species: C. arnoldiana, C. bengalensis, C. carrissoi, C. kapakata, C. ligustroides and C. racemosa. Their chromosome lenghts were compared with those of some previously studied species. These comparisons justified the grouping, proposed by some authors, of C. arnoldiana and C. liberica, C. bengalensis and C. horsfieldiana, C. ligustroides and C. racemosa. C. kapakata may be brought together with the two latter species. No difference appears between the different idiograms observed in the genus.     

Genes conferring low seedling reaction to Mexican pathotypes of Puccinia recondita f. sp. tritici,and adult-plant responses of recent wheat cultivars from the former USSR

Fifty-five spring bread wheat (Triticum aestivum L.) cultivars, mostly released between 1975 and 1991 in eight leaf rust-prone spring wheat growing regions of the former USSR, were tested in the seedling growth stage for reaction to 15 Mexican pathotypes of Puccinia recondita f. sp. tritici. In total, seven known and at least two unknown genes were identified, either singly or in combinations: Lr3 (7 cultivars), Lr10 (14), Lr13 (5), Lr14a (1), Lr16 (1), Lr23 (3); the unknown genes were identified in 14 cultivars. The first unknown gene could be either Lr9, Lr19, or Lr25; however, the second unknown gene in 9 cultivars was different from any named gene. Twelve of the 15 pathotypes are virulent for this gene, hence its use in breeding for resistance will be limited. The cultivars were also evaluated at two field locations in Mexico with two pathotypes in separate experiments. The area under the disease progress curve and the final disease rating of the cultivars indicated genetic diversity for genes conferring adult plant resistance. based on the symptoms of the leaf tip necrosis in adult plants, resistance gene Lr34 could be present in at least 20 cultivars. More than half of the cultivars carry high to moderate levels of adult plant resistance and were distributed in each region.     

Variation in response to infection with Erysiphe graminis hordei and Puccinia hordei in some wild barley populations in a centre of diversity

Summary The Near East Fertile Crescent extending from Iran to Israel is the centre of origin of cultivated barley and a region of great genetic diversity in wild barley, Hordeum spontaneum C. Koch (syn. H. vulgare ssp. spontaneum (C. Koch Thell)). Wild barley accessions collected from different parts of this region were evaluated for their reactions to infection with three isolates of Erysiphe graminis hordei and two of Puccinia hordei. One culture of each pathogen was isolated in Israel and the others, either in Japan or the United States. Out of a total of 330 wild barley accessions collected from 14 sites in Iran, Turkey and Syria, only 18.8% were resistant to the Israeli culture, and 14.8% were resistant to a composite of the Japanese and American cultures of E. graminis hordei. Out of 105 accessions collected from six sites in Iran and Turkey, none was found to be resistant to the Israeli culture and 34.3% were resistant to the American culture of P. hordei. Considerable variation was observed both within and among sites for reactions to infection with different cultures of each of the two pathogens. The results of this study were compared with those of an earlier study involving wild barley accessions from Israel to illustrate the relative importance of different subregions in the Near East Fertile Crescent as sources of new genes for resistance to E. graminis hordei and P. hordei. Implications of these studies for in situ conservation of genetic diversity in wild barley are discussed.     

Genes for Resistance to Yellow Rust in Seedlings of Wheat Cultivars from Pakistan Tested with British Isolates of Puccinia striiformis

Seedlings of 26 wheat caltivars from Pakistan were tested with 18 British races of P. striiformis. It is postulated that the race-specific genes Yr6, Yr7, Yr9 and perhaps Yr2 were present among the cultivars, and that there was other resistance not controlled by these genes.     

Prehaustorial resistance to the wheat leaf rust fungus, Puccinia triticina, in Triticum monococcum (s.s.)

Diploid wheat, Triticum monococcum s.l., is a host for the wheat leaf rust fungus, Puccinia triticina. Some accessions have been reported to show a high degree of prehaustorial resistance. This is non-hypersensitivity resistance, which acts before the formation of haustoria by the pathogen. To assess the frequency of prehaustorial resistance 598 accessions of diploid wheat were inoculated with the wheat leaf rust isolate Felix. Most T. monococcum s.s. accessions (84%) were resistant whereas all T. urartu and all but three T. boeoticumaccessions were susceptible. Histological components analysis revealed that a high percentage of prehaustorial resistance to P. triticina was found in only three T. monococcum accessions. No haustoria were observed in such infection units confirming the prehaustorial nature of the resistance. Prehaustorial abortion of certain infection units in an accession always coincided with posthaustorial abortion of the other infection units. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic diversity estimates in Cicer using AFLP analysis

Amplified fragment length polymorphism (AFLP) analysis was used to evaluate the genetic variation among cultivated chickpea and wild Cicer relatives. In total, 214 marker loci were assessed, of which 211 were polymorphic (98.6%) across the 95 accessions that represented 17 species of Cicer. The genetic variation within a species was highest in C. pinnatifidum followed by C. reticulatum and lowest in C. macracanthum. Three main species groups were identified by UPGMA clustering using Nei's pair‐wise distance calculations. Group I included the cultivated species C. arietinum, C. reticulatum and C. echinospermum. Within this group, C. reticulatum accessions were clustered closest to the C. arietinum cultivars ‘Lasseter’, ‘Kaniva’ and ‘Bumper’, supporting the hypothesis that C. reticulatum is the most probable progenitor of the cultivated species. Cicer bijugum, C. judaicum and C. pinnatifidum were clustered together creating group II. Group III contained all nine perennial species assessed and two annual species C. yamashitae and C. cuneatum. The genetic distance detected between group I and group III (0.13) was equivalent to the genetic distance detected between group I and group II (the primary and annual tertiary species, respectively; 0.14). This indicated that the perennial tertiary species may be as valuable for increasing variation to incorporate novel germplasm in the cultigen as the annual tertiary species.     

Application of Triticum monococcum for the improvement of triticale resistance to leaf rust (Puccinia triticina)

The aim of this work was to evaluate the leaf rust resistance introduced into introgressive triticale lines with Triticum monococcum genes, and to study the expression of these genes at the hexaploid level. The introgressive lines were developed by incorporating diploid wheat (T. monococcum s.s.) genes into hexaploid triticale LT 522/6 using the synthetic allotetraploid T. monococcum/Secale cereale (A^mA^mRR) as a bridging form. A group of 44 those lines, parental stocks and check cultivars were inoculated at the seedling stage (in a greenhouse) and at the adult‐plant stage (in the field) with four pathotypes of Puccinia triticina. At the seedling stage the assessment of infection type showed that four lines had resistance to all pathotypes as high as in the T. monococcum donor. Adult plant examinations showed some introgressive lines with complete resistance and also lines with partial resistance, expressed in area under the disease progress curve (AUDPC) calculations as slow rusting. Some lines comprise low AUDPC with complete resistance at seedling stage.