The inheritance of stem rust and leaf rust resistance in some Ethiopian wheat collections

Summary Common and durum wheat populations obtained from Sweden and originally collected in Ethiopia were screened for resistance to steum rust and leaf rust. Resistant selections of common wheat were crossed and backcrossed with either stem rust susceptible RL6071, or leaf rust susceptible Thatcher. Genetic studies, based largely on tests of backcross F₂ families, showed that four of the selections had in common a recessive gene SrA. Plants with this gene were resistant (1⁺ infection type) to all stem rust races tested. This gene was neither Sr26 nor Sr29. The resistance of other selections, based on tests with an array of rust isolates, was due to various combinations of Sr6, 8a, 9a, 9d, 9c, 11, 13, 30, and 36. One of the selections had linked genes, Lr19/Sr25. Another selection had a dominant gene for resistance (;1 infection type) to all the races of leaf rust. With the possible exception of this gene for leaf rust resistance and SrA, no obviously new resistance was found.     

Identification and characterization of partial resistance to rust in a germplasm collection of Lathyrus sativus L.

Lathyrus sativus has high potential both as food and fodder crop but can be severely infected by rust. This study assessed the resistance level of a collection of L. sativus accessions against three rust species ( Uromyces pisi , U. ciceris-arietini and U. viciae-fabae ) and characterized, for the first time, macro and microscopically the resistance to U. pisi . All L. sativus accessions were highly resistant to U. ciceris-arietini and to U. viciae-fabae but showed a compatible interaction with U. pisi. However, in spite of this compatible interaction, high levels of rate reducing resistance were identified with significant disease severity reduction, fitting the Partial Resistance definition. Detailed histological observations showed that resistance was mainly because of haustorium formation restriction with high-level of colony early abortion, and reduction in the haustoria number per colony. This was occasionally associated with reduction on the infection hyphae intercellular growth, in a clear example of prehaustorial resistance. Differences in germination, orientated germ tube growth and appressoria differentiation were observed but were, generally, of marginal importance to explain the observed resistance levels.     

Components of rust resistance in lentil

Four components of resistance to Uromyces viciae-fabae, namely, latent period (LP), infection efficiency (IE), pustule size (PS) and spore production (SP) were evaluated on lentil (Lens culinaris) in glasshouse experiments. Four cultivars, Gudo, R-186, FLIP-87-66L and FLIP-89-60L, with different levels of resistance, and the susceptible check EL-142, were included in this study. The cultivars were also compared for area under the disease progress curve (AUDPC), area under the pustule density curve (APDC), apparent infection rate (r_G), disease severity (DS), pustule density (PD), LP and PS under field conditions. Gudo and R-186 had significantly smaller and fewer pustules, lower spore yield and longer latent period than EL-142. FLIP-87-66L was intermediate for infection efficiency and pustule size. In addition, significant differences were found between cultivars for AUDPC, APDC, DS and r_G. Estimates of AUDPC, APDC, DS and r_G were reduced in Gudo, R-186 and FLIP-87-66L compared with the susceptible check EL-142. FLIP-89-60L also showed low AUDPC, APDC and DS. Some of the components obtained in the field were significantly correlated with each other (r = 0.92–0.99, P 0.05) and those measured in the glasshouse. Most of the components studied in the glasshouse were significantly (P 0.05) correlated with AUDPC and DS. Data indicated the existence of incomplete [partial (PR)] resistance in the test cultivars, and the possibility of using IE, LP, SP and PS as selection criteria in the evaluation of PR to rust in lentil. Since there was an interdependence of the components, selection based on more than one component should help obtain lines with higher levels of PR. The AUDPC, DS and r_G could also be used for selecting lines with PR in the field.     

The phenotypical responses of gladiolus germplasm with different degrees of resistance to Uromyces transversalis

Summary The evaluation of populations of breeding lines, cultivars and species of the genus Gladiolus resulted in the development of an evaluation schedule and a standardized artificial inoculation technique. The entire population of cultivars that was evaluated is susceptible to Uromyces transversalis. However, some breeding lines and species were almost immune to gladiolus rust.     

Transgressive segregation for resistance to yellow rust in wheat

Summary Crosses were made between wheat varieties Joss Cambier, Nord Desprez and Maris Bilbo, all classified as susceptible to yellow rust in field tests, and between Cappelle Desprez and Maris Huntsman, both classified as moderately and durably resistant. Selection for resistance to yellow rust among the progeny was carried out using races of Puccinia striiformis able to overcome all the known race-specific components of resistance in both parents of each cross. Lines with greater resistance than in both parents were obtained from each cross, those with greatest resistance being obtained from the cross between the moderately resistant parents. Three lines selected for resistance from the cross of Joss Cambier with Nord Desprez and one from the cross of Cappelle Desprez with Maris Huntsman, together with the parents, were tested in the field with 12 races of P. striiformis. Nord Desprez possessed a previously undetected race-specific component. The selected lines also displayed race-specific resistance, some of which was clearly related to race-specificity of the parents, and a component of resistance, greater than in both parents, that was effective against all 12 races. The possible origin and potential durability of this transgressive level of resistance is discussed. It is suggested that such transgressive resistance is more likely to be durable if it is derived from parents that have shown durable resistance.     

Genes for resistance to stripe rust in four spring wheat varieties

Summary Four spring wheat (Triticum aestivum L.) varieties differing in origin and reaction in the seedling stage to pathotype CDL-6 (extant in California) were intercrossed and examined in greenhouse conditions in F₁, F₂, and F₃ generations. Digenic and transgressive segregation was found in all crosses. The four varieties each had infection types (1 immune, 9 susceptible) and putative resistance genes as follows: Anza, IT 7, YrA; Glennson 81, IT 2, Yr9; Yecora Rojo, IT 6, YrC; and Ollanta, IT 4–6, YrL. Anza was classified as susceptible, Yecora Rojo and Ollanta as intermediate in seedling resistance, and Glennson 81 as resistant in the seedling stage.     

An analysis of genes for resistance against Indian stem rust races in two bread wheat cultivars

Summary The genetic constitution of two bread wheat accessions from the International Spring Wheat Rust Nurseries (E 5883 and E 6032) has been studied for reaction to four Indian races of stem rust. Analysis of E 5883 has revealed that for each of the races 15C, 21 and 40 a single dominant gene operates for resistance. The dominant gene against race 15C was identified as Sr6. The dominant genes for resistance against races 21 and 40 were found to be different from the genes described so far. Resistance against race 122 is controlled by a single recessive gene producing characteristically a 2 type of reaction. This gene was identified as Sr8.The resistance of E 6032 against each of the races 15C, 21 and 40 is controlled by two genes, one dominant and one recessive, which act independently. Dominant genes effective against 15C, 21 and 40 were conclusively identified as Sr6, Sr5 and Sr9b, respectively. From the correlated behaviour against races 15C and 40 as well as from the phenotypes of the resistance reactions rhe same recessive gene, undescribed so far, operates against the two races. The second recessive gene operating against race 21 was also observed to be different from those so far designated. E 6032 was, however, found to be susceptible to races 122.The presence of Sr6 both in E 5883 and E 6032 against race 15C was further confirmed through F₂ and F₃ segregation data.     

Genes for resistance to stripe rust in four spring wheat varieties

Summary The stripe rust resistant spring wheat (Triticum aestivum L.) varieties Anza, Glennson 81, Ollanta, and Yecora Rojo gave 1,2,2, and 2-gene segregations, respectively, in hybrids with susceptible Jupateco 73 when inoculated in field conditions at Davis, California USA with Puccinia striiformis West. pathotype CDL-6 and rated at post-heading stage. Intercrosses of these varieties, Anza/Yecora Rojo was not studied, permitted the following conclusions about the genes expressed in adult plants: Anza, one recessive gene; Glennson 81, two dominant genes; Ollanta, two genes, at least one is dominant; and Yecora Rojo; one dominant and one recessive gene, one of which is common with Ollanta. The resistance genes in these varieties, which expressed resistance in the seedling stage, were believed to be effective at the adult stage. Thus, seven resistance genes were identified in the four varieties. The genotypes were designated for the purposes of this study as follows: Anza, YrA YrH; Glennson 81, Yr9, YrJ, Ollanta YrL YrD; and Yecora Rojo, YrC YrD. It was recommended that these and other Yr genes be used as multiple gene complexes to increase durability of resistance to P. striiformis, an organism known to evolve virulence rapidly in field conditions. The demonstrated durability of Anza in California may be a result of its combination of resistance alleles at two loci.     

Enhanced leaf rust resistance in wheat conditioned by resistance gene pairs with Lr13

Summary Leaf rust resistance gene Lr13 is present in many North American hard red spring wheat cultivars that have shown durable resistance to leaf rust. Fifteen pair-wise combinations of Lr13 and seedling leaf rust resistance genes were developed by intercrossing near isogenic Thatcher lines. In both seedling and adult plant tests, homozygous paired combinations of specific resistance genes with Lr13 had enhanced resistance relative to either parent to rust isolates that had intermediate avirulent infection types to the additional genes. In field tests, homozygous lines were more resistant than either parent if the additional leaf rust gene conditioned an effective level of resistance when present singly.     

Effectiveness of genes for leaf rust resistance in international wheat rust nurseries, 1970–1975

Monogenic lines resistant to leaf rust of spring and winter wheats were grown in the world wheat-producing areas from 1970 through 1975. Lines containing the alleles Lr9 (Wi), Lr9 (Tc), and Lr19 (Tc) were more resistant to the leaf rust pathogen than those containing Lr1 (Tc), –1 (Wi), –1,3 (Wi), –2A (Tc), –2A (Wi), –2D (Tc), –3 (Tc), –3 (Wi), –10 (Tc), –16 (Tc), –17 (Tc), –18 (Tc), or –2D (Pld). Monogenic line Lr1 (Wi) possibly has more than one gene for resistance and resistance properties similar to cultivars with field resistance. A computer data base was created to produce the information used in this paper.Formerly Research Agronomist, Field Crops Laboratory, now Supervisoty Computer Specialist, DSAD; and Research Plant Pathologist, Germplasm Resources Laboratory, ARS, BARC-West, Beltsville, Maryland 20705.     

The genetics of seedling resistance to leaf rust,Puccinia hordeiOtth. in some spring barley cultivars

Summary The three Dutch isolates studied carried virulence genes against the resistance genes Pa, Pa-2, Pa-4 and Pa-5, substantiating the widespread occurrence of these virulences in Western Europe as reported by others. The cultivars Cebada Capa, La Estanzuela, Gondar and Dabat carry the same dominant to semi-dominant gene, which is also found in Forrajera Klein and H2212. It is proposed to designate this gene Pa-7. This gene segregated independently from the Pa-3 gene in Rika x (Baladi x Rika) substantiating the data of Johnson (1968), but disagreeing with those of Roane & Starling (1970). EP 75 seems to carry a single dominant or semi-dominant gene conferring an intermediate resistance to the isolates used. This gene, tentatively designated as Pa-z, is different from the Pa, Pa-2, Pa-4, Pa-5 and Pa-7 genes. The intermediate resistance of Monte Christo is probably based on gene(s) different from EP 75.     

Monosomic analyses of stripe rust and leaf rust resistance genes in winter wheat varieties Lüquyu and Yantar

Summary A set of 21 monosomics of Novosadska Rana-1 was used to locate the rust resistance genes of Lüqiyu, a stripe rust resistant line developed by BAU and Yantar, a leaf rust resistant wheat introduced from Bulgaria. The resistance of the former to p. striiformis race C25 was conditioned by a dominant gene located on chromosome 2B, whereas that of the latter to P. recondita race CL3 was controlled by two complementary dominant genes located on chromosomes 5A and 1D, respectively. The relationship of the stripe rust resistance gene in Lüqiyu to Yr5, Yr7 or Yr _Suwon' all located on chromosome 2B is unknown. The two complementary leaf rust resistance factors in Yantar appear to be new.     

Identification and cataloguing of genetic information for resistance to wheat leaf rust

Summary Specific host-pathogen relationship is used to derive genetic information for resistance in commercial cultivars. Twenty-two cultivars were classified into 12 groups based on their reactions to 13 leaf rust (Puccinia recondita) races of India. The cultivars in each group were matched with the Lr gene carrying lines to see which genes they might possess. Confirmation of this information was sought through pedigree analyses.(1) Agra local and NP4 do not seem to have any resistance genes. (2) C306 has gene Lr14a, and NP824 one of the genes Lr12, Lr13, Lr14a or Lr22. (3) kalyansona carries Lr13 and another additional gene not in study. (4) Chhoti Lerma, NP852, Pusa Lerma, Sharbati Sonora, Shera, UP301 form one group and carry Lr1. (5) Sonalika seems to have Lr2a, Lr11 and additional genes. (6) Hy.65 has Lr10. (7) HS1076-2 and HW135 have the genes Lr2a and Lr3do. (8) HW124 carries the genes Lr1 and Lr3do. (9) Safed Lerma has Lr1 and Lr17. (10) NP846 has the genes Lr1 and Lr15. (11) HB117-107, Janak, UP215 form one group and possess the genes Lr3do and Lr15. (12) Girija possesses the genes Lr10 and Lr15.Based on such grouping of commercial cultivars for resistance genes a Catalogue system is advocated for the design of wheat breeding programmes like the development of multiline and multigene cultivars.     

Allelism of two genes for stem rust resistance in triticale

Summary Inheritance studies involving Coorong and Satu triticales showed that each possessed a single dominant gene for resistance. The genes were allelic or closely linked. The relative frequencies of Sr27 (Coorong gene) and Sr _Satuin a sequence of International Triticale Screening Nurseries were similar. However, a significant increase in the frequency of entries with Sr_Satu occurred in the 17 International Triticale Screening Nursery (ITSN).     

Interplot interference and the assessment of barley cultivars for partial resistance to leaf rust,Puccinia hordei

Summary The barley cultivars Akka, highly susceptible, and Vada, partially resistant to barley leaf rust, Puccinia hordei, were evaluated for the amount of leaf rust in five experimental field plot situations over three successive years. The field plot situations were: A) plots well isolated from each other by distance and non-leaf rust contributing host plants; B) adjacent plots of 4×41/2 m (18 rows); C) adjacent plots of 4×11/2 m (6 rows); D) adjacent plots of 4×1/4 m (1 row); E) adjacent plots of only one plant (cultivar mixtures).The sporulating leaf area of each plot was measured from samples of 20 tillers taken at random from each plot. In each year the difference in sporulating area between Akka and Vada was large to very large in the absence of interplot interference in the isolated plots, ranging from 150 to 2100 times. In the adjacent plots the partial resistance of Vada was greatly underestimated, 5 to 16 times in the situation B, 14 to 30 times in C, and 75 to 130 times in D and E.Testing lines or cultivars in adjacent plots is the standard procedure in use in breeding programs and in tests of cultivars for their agricultural value. To avoid such under estimation the following procedure is suggested. A few cultivars representing the known range of partial resistance and whose level of partial resistance is well known are evaluated together with the lines and cultivars whose partial resistance has to be assessed. This is demonstrated with a number of cultivars of which resistance values are know from the recommended variety lists for England and Wales. Cultivars have been assessed in Wageningen over four years together with the check cultivars Akka, Sultan, Julia and Vada representing the range of partial resistance with values (on a 1 to 10 scale) of 1, 3–4, 7 and 8 respectively, based on isolated plots experiments.     

Virulence of wheat yellow rust races and resistance genes of wheat cultivars in Ecuador

Virulence factors of the yellow rust, Puccinia striiformis, populations in bread wheat were studied in Ecuador between 1973 and 2004. The number of virulence factors has increased markedly from very few in the early seventies to 16 at the end of the 90s. Isolates belonging to race 0E0 seem to be the ancestor of a rapid virulence evolution of yellow rust in Ecuador. This evolution can be explained by a single step mutation pattern. Virulence to the resistance genes Yr1, Yr2, Yr2+, Yr3V, Yr3ND, Yr4+, Yr6, Yr6+, Yr7, Yr7+, Yr9, Yr9+, Yr11, Yr12, Yr18, Yr24, Yr26 and those in the cultivars Carstens V (YrCV) Strubes Dickkopf (YrSD), Suwon92/Omar (YrSU), Spaldings Prolific (YrSP), Anza (YrA+) and Selkirk (YrSK). was identified. Virulence to Yr5, Yr8, Yr10, and Yr15 was not found. Postulation of resistance genes at the seedling stage of 14 Ecuadorian wheat cultivars indicated that these cultivars carry alone or in combinations the resistance factors Yr1, Yr2, Yr3, Yr6, Yr9 and/or other undesignated resistance factors. Yellow rust evolution in Ecuador has been associated with deployment of these resistance genes. None of these deployed Yr resistance genes are effective to the present yellow rust population in Ecuador.     

Variation of characters in near-isogenic lines of wheat with added genes for leaf rust resistance

Summary Using the cultivar Arina as the recurrent parent, six backcrosses were made with two donor lines carrying the leaf rust resistance genes Lr1 and Lr9, respectively. Selection for leaf rust resistance occurred at the seedling stage in the greenhouse; the first plants transferred to the field were BC₆F₄s. Frequency distribution of the 332 Lr1/7 × Arina and the 335 Lr9/7 × Arina lines showed continuous variation for yellow rust resistance and heading date in these leaf rust near-isogenic lines (NILs). Similar results were also obtained for plant height, for resistance to powdery mildew and glume blotch, as well as for baking quality characters in another set of more advanced NILs. The available information on the behaviour of one of the parents of cultivar Arina led to the conclusion that the expressed yellow rust resistance is quantitative and might possibly be durable.     

Evaluating faba beans for rust resistance using detached leaves

A method was developed for testing detached leavesof faba beans for their response to rust disease.Leaves 5 to 8, counting from the shoot tip, wereexcised and maintained on a water-retaining medium,with 5 ppm gibberellic acid, in an enclosed box in atemperature-controlled glasshouse. Leaves treated inthis way remained in good health for up to 30 days.Rust spores were dispersed in a slurry of talc andwater and applied to the abaxial leaf surface. Diseasedevelopment of seven rust populations, collected fromseveral locations in eastern Australia, was monitoredfor 15 days on eight faba bean accessions. Fouraccessions were BPL lines which ICARDA claimed to havesome resistance, two were ILB lines from ICARDA whichhad been found to have stronger field resistance innorthern New South Wales, Australia, and the remainingtwo were known susceptibles. The detached-leaf testshowed that the two cultivars were susceptible, thefour BPL lines were intermediate and ILB 3107 and ILB3025 were slow-rusting. One rust population, which hadbeen stored under liquid nitrogen for several years,was less effective at inducing disease symptoms thanthe other six, which were all freshly collected. Theinteractions between host accessions and rustpopulations were statistically significant but minor,as the cultivars remained in their categories ofresistance or susceptibility. The detached-leaftechnique is thus suitable for use in screeningindividual plants for reaction to several differentpathogen species or genotypes without danger ofcross-contamination or induced resistance.     

Genetics of leaf rust resistance in 13 accessions of the Watkins wheat collection

Summary The inheritance of leaf rust resistance was studied in 13 accessions of the A.E. Watkins wheat collection. Eight of the accessions (V409, V624, V628, V712, V731, V734, V745, and V855) were shown to have gene Lr33 and four of these (V409, V624, V628, and V731) also have LrW. Accessions V624 and V338 have LrB, and V377 and V488 have Lr11. V46 has an unidentified gene that gives an intermediate level of resistance. V860 has a partially dominant gene that gives a fleck reaction to avirulent isolates in the seedling stage. This gene is different from LrW and may be previously unidentified. It has been assigned the temporary gene symbol LrW2. In addition to seedling-effective genes, V46, V731, and V745 may have Lr34 and V745 may have Lr13. The adult-plant resistance in V488, V624, and V860 could not be identified. Seedling gene LrW2 and some of the adult-plant resistance should be useful sources of resistance.Contribution NO. 1576.     

Characterisation and origin of rust and powdery mildew resistance genes in VPM1 wheat

Summary The expression of rust resistances conferred by closely linked genes derived from VPM1 varied with environmental conditions and with genetic backgrounds. Under low light and low temperature conditions seedlings carrying Yr17 showed susceptible responses. Stem rust and leaf rust resistance genes Sr38 and Lr37 tended to confer more resistance at 17±2° C than at normal temperatures above > 20° C. These studies supported the hypothesis that Yr17, Lr37 and Sr38 were derived from Aegilops ventricosa, whereas Pm4b was probably derived from T. persicum. Studies on certain addition lines and parental stocks indicated that wheat cytoplasm may enhance the expression of Sr38.