Inheritance Of Leaf Rust Resistance Research Articles

Inheritance of leaf rust resistance in four popular Indian durum wheat cultivars

Leaf rust is the one of the most important biotic stresses affecting world wheat production because of its wide distribution. In a study conducted to understand the inheritance of leaf rust resistance genes present in the popular durum wheat cultivars viz. HI 8498, HI 8663, HI 8713 and HI 8737 indicated that a single dominant gene each controls resistance to two Puccinia triticina (Pt) pathotypes 162-2 (93R39) and 104-2 (21R55). The allelic tests indicated that three diverse genes control resistance to Pt pathotype 104-2, with the gene being common between HI 8713 and HI 8737. Resistance to pathotype 162-2 was controlled by two diverse genes among the four test cultivars as the same gene conditioned resistance in HI 8737, HI 8713 and HI 8663 with the resistance gene in HI 8498 being different. The infection types of the two Pt pathotypes on the test cultivars were found to be higher than that of near isogenic lines carrying Lr3, Lr14a and Lr23 indicating that the identified genes in the present study were different from these commonly postulated Lr genes in Indian durum germplasm. The identified leaf rust resistance genes in the study will contribute to the diversity of leaf rust resistance in durum wheat and can be well utilized in breeding programmes.

Genetic analysis of leaf rust resistance in three common wheat cultivars MP 3288, HI 784 and HI 1418 under field conditions

This study aimed to investigate the genetic basis of leafrust resistance in three bread wheat cultivars viz., MP 3288, HI 1418 and HI 784 which have been maintaining high levels of resistance to leaf rust since their release in 2011, 2000, and 1983, respectively. These cultivars also possess leaf tip necrosis phenotype. These were crossed with a susceptible bread wheat cultivar Lal Bahadur and also among themselves in non-reciprocal manner.The F1 , F2 and F3 populations were raised and the inheritance of leaf rust resistance was studied using prevalent and highly virulent Puccinia triticina pathotype 77-5 (121R63-1) during 2014- 17. These studies showed that the field (adult-plant) resistance of these cultivars is governed by two dominant genes each. Closely linked molecular markers L34DINT9F and L34PLUSR revealed the presence of non-race specific adult-plant leaf rust resistance gene Lr34 in all cultivars of present study. Absence of the other documented race nonspecific APR genes viz., Lr46, Lr67 and Lr68 was indicated in all the three test cultivars based on genotyping with closely linked molecular markers WMC44, CFD71 and csgs, respectively. The other dominant gene appears to be an allstage resistance gene since all the three cultivars displayed high levels of seedling resistance to the test pathotype. Stable resistance of these cultivars could be due to synergistic/additive or complementary effects resulting from the combination of Lr34 and the all-stage resistance gene.

English

Leaf rust is a major disease of wheat crop in the world as a whole. This study was undertaken to find the genetic effects of adult plant leaf resistance in wheat (Triticum aestivum L.). Three wheat crosses were developed from three resistant and one susceptible parent. Six populations (P1, P2, F1, F2, BC1 and BC2) of each cross were grown under field conditions and were artificially inoculated with isolates of mixture of leaf rust prevalent races. Leaf rust intensity and reaction type were observed and the coefficient of infection was computed. Generation means and variance analyses were performed for the estimation of additive, dominance and epistatic genetic effects. Additive and dominance, as well as epistatic genetic effects, are involved in the inheritance of leaf rust resistance. However, the narrow sense heritability estimates were low, which also exhibited the presence of epistatic genetic effects. Thus, selection of resistant adult plant in later segregating generations would be useful for the development of high yielding wheat genotypes.   Key words: Wheat, leaf rust, Puccinia recondite, genetic studies, Pakistan.

The inheritance of leaf rust resistance in the wheat cultivars ‘Superb’, ‘McKenzie’ and ‘HY644’

Understanding the genetic resistance to wheat leaf rust, caused by Puccinia triticina, in Canadian wheat cultivars is critical for maximizing resistance in future-bred cultivars. This knowledge also helps to predict the impact of changes in virulence to specific resistance genes within the P. triticina population. ‘Superb’ and ‘McKenzie’ are two of the most popular high-yielding wheat cultivars in Canada. ‘HY644’ has moderate resistance to Fusarium head blight (caused primarily by Fusarium graminearum). All three of these cultivars have been used extensively as parents in Canadian wheat breeding programmes. To analyze the nature of resistance in these cultivars, they were crossed and then backcrossed to the susceptible cultivar ‘Thatcher’. The BC1F3 populations were inoculated at the seedling and adult plant stages with various P. triticina races to determine the number and identity of the resistance genes in each cultivar. Allelism tests, to confirm the postulated genes, were performed by crossing each cultivar to the ‘Thatcher’ isolines containing the postulated genes and analyzing the F2 progeny for rust resistance. ‘Superb’ was demonstrated to have genes Lr2a and Lr10, ‘McKenzie’ had Lr10, Lr13, Lr16 and Lr21, and ‘HY644’ had Lr1, Lr17, Lr34 and an unknown resistance gene.

Inheritance and QTL mapping of leaf rust resistance in the European winter wheat cultivar ‘Beaver’

Genetic studies were conducted on an European winter wheat cultivar, Beaver, to determine the mode of inheritance of leaf rust resistance at seedling and adult plant growth stages using a recombinant doubled haploid population, Beaver/Soissons. Greenhouse studies indicated the involvement of genes Lr13 and Lr26 in governing leaf rust resistance at seedling growth stages, whereas, adult plant resistance (APR) in the field with pathotypes carrying virulence individually for Lr13 and Lr26 showed trigenic inheritance for the population. Marker regression analysis of adult plant field data indicated the involvement of six significant QTLs (chromosomes 1B, 3B, 3D, 4B, 4D and 5A) in year 2005, four QTLs (1B, 3B, 4B and 5A) in 2006, and six QTLs (1A, 1B, 3B, 4A, 4B and 5A) in 2007 for reducing leaf rust severity. QTLs on chromosomes 1B, 4B and 5A were considered the most important because of their detection across years, whereas QTLs on chromosomes 1A, 3B, 3D and 4A were either inconsistent or non-significant and unexplained. Based on an association of closely linked markers with phenotypic data, putative single gene stocks were identified for each consistent QTL and crossing was initiated to develop populations segregating for each to permit fine mapping of the identified regions.

Chromosomal location in triticale of leaf rust resistance genes introduced from Triticum monococcum

AbstractThis study was undertaken to understand the inheritance of leaf rust resistance in line TM16 of Triticum monococcum ssp. monococcum var. macedonicum Papag. which is the source of resistance transferred into hexaploid triticale lines (Tcl/Tm). Thirty‐two secondary tetraploid genotypes were analysed cytologicaly to identify substitutions of Am‐genome chromosomes by their homoeologous A‐genome chromosomes from a leaf rust susceptible hexaploid triticale accession. Plants with one (or more) substituted chromosomes were inoculated with leaf rust at two growth stages. The disease phenotypes of these lines indicated that a major resistance gene was located on the short arm of T. monococcum chromosome 2Am. An additional gene on chromosome 6Am had complementary effects in enhancing the effects of the gene on chromosome 2Am.

Inheritance of leaf rust resistance in wheat lines carryingAegilops speltoides Tausch. translocation in Chinese Spring background

The genetic basis of seedling and adult-plant leaf rust resistance was analysed in wheat lines CS 2A/2M 4/2 and CS 2D/2M 3/8, which are reference lines for the leaf rust resistance gene Lr28. Some seedlings of CS 2A/2M 4/2 were susceptible to Indian Puccinia triticina (Pt) pathotypes 77-1, 77-2 and 77-5. These susceptible seedlings exhibited resistance at the adult-plant growth stage. In contrast, CS 2D/2M 3/8 showed resistance to all Pt pathotypes both at the seedling and adult-plant growth stages. The analysis of inheritance in the susceptible plants of CS 2A/2M 4/2 (CS 2A/2M 4/2 APR selection) and CS 2D/2M 3/8 against Pt 77-5 (the frequently occurring Pt pathotype from the Indian subcontinent), indicated that line CS 2D/2M 3/8 was fixed for a dominant gene, presumed to be Lr28, whereas line CS 2A/2M 4/2 was heterogeneous for Lr28. The adult-plant resistance in the CS 2A/2M 4/2 APR selection was conferred by an unknown recessive gene.

Inheritance of Leaf Rust Resistance in the CIMMYT Wheat Weebill 1

The CIMMYT spring wheat Weebill 1 has near‐immune levels of adult plant resistance (APR) to leaf rust caused by Puccinia triticina Eriks. To determine the genetic basis of resistance in seedlings and adult plants Weebill 1 was crossed with two susceptible parents Jupateco 73S and ‘Thatcher’. Advanced F4:5, F4:6, and F5:7 recombinant inbred lines (RIL) populations from Jupateco 73S/Weebill 1 and BC1F2 populations from Thatcher/Weebill 1 were derived. The F5:7 RILs and BC1F2 families were tested as seedlings with five races of P. triticina The F1 and F4:5, F4:6, and F5:7 RILs of Jupateco 73S/Weebill 1 were evaluated in plots in Mexico and St. Paul. The Jupateco 73S/Weebill 1 RILs and Thatcher*2/Weebill 1 F2 families segregated for Lr14b, an unknown seedling leaf rust resistance gene derived from Weebill 1 in both crosses, and Lr17a derived from Jupateco 73S in the RIL population. Lr17a was mapped to the distal end of chromosome 2AS and was linked to microsatellite maker Xgwm636 at a distance of 4.0 cM. The seedling genes did not condition effective resistance in the field plots with races used in the field trials. The segregation ratio in the RILs and F2 families indicated the presence of three to four APR genes in Weebill 1. One of the APR genes was linked to the seedling gene Lr14b on chromosome 7BL and reduced leaf rust by 47% in St. Paul and 31% in Mexico. Based on the haplotypes of DNA markers, we do not believe that any of the APR genes is Lr34

Detection and inheritance of leaf rust resistance in common wheat lines Agra Local and IWP94

Genetic studies were undertaken to determine the number and identities of leaf rust resistance genes in common wheat lines Agra Local and IWP94. The infection type arrays of the two lines with eight pathotypes (pt.) of P. triticina were different from those of lines possessing known leaf rust resistance (Lr) genes. Agra Local possessed two recessive resistance genes, one conditioning resistance to pathotype 4R9-7, and the other, a temperature-sensitive factor, gave resistance to pt. 121R127 at high temperature (27°C). IWP94 was previously demonstrated to carry Lr23. From the present study IWP94 was determined to have at least four leaf rust resistance genes. The first of these was the same recessive gene conferring resistance to pathotype 4R9-7 which was found in Agra Local. A second partially dominant gene conferred resistance to pathotype 121R127 at high temperature and two additional recessive genes governed resistance to pathotype 93R15. When present together, these two recessive genes complemented each other and provided resistance to pathotype 69R13 as well. One of the two recessive genes conferring resistance to pathotypes 93R15 and 69R13 was Lr23.

The Effect of Lr19-Translocation on in Vitro Androgenesis and Inheritance of Leaf-Rust Resistance in DH3Lines and F2Hybrids of Common Wheat

Leaf-rust resistance and androgenesis were studied in the anther cultures of Triticum aestivum L., which included Saratovskaya 29 cultivar, the isogenic line Ps29, and three F1 hybrids (L503/S55, L504/S58, ATS7/L1063) with 7DS-7DL-7Ae#1L translocation of Lr19 gene (Lr19 translocation) from Agropyron elongatum (Host) P.B. The Lr19 translocation was shown to affect the induction of embryogenesis and green plant regeneration. The frequencies of Lr19 translocation differed in F2 hybrids obtained by traditional hybridization and in sets of DH lines obtained in F1 anther cultures derived from the same combinations of T. aestivum parental forms. The number of leaf-rust resistant genotypes tended to decrease. The frequency of Lr19 translocation in the set of DH3 lines derived from F1 L504/S58 was significantly lower than in other sets of DH3 lines and F2 hybrid populations.

Inheritance of leaf rust resistance in the wheat cultivars AC Majestic, AC Splendor, and AC Karma

The wheat cultivars AC Majestic, AC Splendor, and AC Karma were developed and licensed for production in western Canada in the mid-1990s. Leaf rust, caused by Puccinia triticina, is an important pathogen of wheat throughout North America. Virulent isolates of P. triticina are selected and increase following the release of wheats with specific resistance genes, which eventually reduces the effectiveness of the resistance. Knowledge of the genes that condition leaf rust resistance in wheat makes it easier to add additional resistance genes to breeding germplasm. The objective of this study was to identify the leaf rust resistance genes in these three cultivars. The three cultivars were crossed with the susceptible wheat 'Thatcher', and the F1 plants were backcrossed to 'Thatcher'. The backcross F2 (BCF2) families were tested for segregation of leaf rust resistance in seedling tests with specific P. triticina isolates. The BCF2 families were also tested for segregation of leaf rust resistance as adult plants in a field rust nursery that had been inoculated with a mixture of P. triticina virulence phenotypes. 'AC Majestic' was determined to have the seedling resistance gene Lr16 and the adult plant resistance gene Lr13. 'AC Splendor' was determined to have Lr13, Lr16, and the adult plant resistance gene Lr34. 'AC Karma' was determined to have Lr13, Lr16, and the adult plant resistance gene LrTb. All three cultivars had genes Lr13 and Lr16, which reflect a lack of genetic diversity for leaf rust resistance in western Canada spring wheats. The results of the study indicate that additional leaf rust resistance genes need to be crossed into the spring wheat germplasm to provide new cultivars with high levels of leaf rust resistance.

Resistance to wheat leaf rust in Aegilops tauschii Coss. and inheritance of resistance in hexaploid wheat.

A collection of 164 Aegilops tauschii accessions, obtained from Gatersleben, Germany, was screened for reaction to leaf rust under controlled greenhouse conditions. We have also evaluated a selection of synthetic hexaploid wheats, produced by hybridizing Ae. tauschii with tetraploid durum wheats, as well as the first and second generation of hybrids between some of these resistant synthetic hexaploid wheats and susceptible Triticum aestivum cultivars. Eighteen (11%) accessions of Ae. tauschii were resistant to leaf rust among which 1 was immune, 13 were highly resistant and 4 were moderately resistant. Six of the synthetic hexaploid wheats expressed a high level of leaf rust resistance while four exhibited either a reduced or complete susceptibility compared to their corresponding diploid parent. This suppression of resistance at the hexaploid level suggests the presence of suppressor genes in the A and/or B genomes of the T. turgidum parent. Inheritance of leaf rust resistance from the intercrosses with susceptible bread wheats revealed that resistance was dominant over susceptibility. Leaf rust resistance from the three synthetics (syn 101, syn 701 and syn 901) was effectively transmitted as a single dominant gene and one synthetic (syn 301) possessed two different dominant genes for resistance.

The transfer of leaf rust resistance from Triticum timopheevii to durum and bread wheat and the location of one gene on chromosome 1A

Triticum timopheevii (Zhuk.) Zhuk. is noted for its resistance to diseases including leaf and stem rust of wheat. Only one gene (Lr18) for leaf rust resistance has been transferred from T. timopheevii to bread wheat. The objectives of this work were to study the inheritance of leaf rust resistance in five accessions of T. timopheevii and to transfer genes for resistance into durum and bread wheats. A diallel set of crosses was made among five T. timopheevii accessions that gave a fleck infection type with an isolate of leaf rust race CBB. None of the F2 populations of the 10 crosses segregated for resistance, indicating that the five accessions all had at least one gene for resistance in common. Several accessions were crossed and backcrossed twice to durum and to bread wheat. At least three genes for leaf rust resistance were transferred to durum wheat and one to bread wheat. The gene transferred to bread wheat and one of those transferred to durum wheat conditioned good resistance to a set of 10 diverse races of leaf rust. Resistance conditioned by all three genes was dominant in durum wheat but the one gene was recessive in bread wheat. Monosomic analysis of the bread wheat line showed that the gene is on chromosome 1A. It should be useful in breeding for leaf rust resistance in both durum and bread wheat. Key words: Triticum timopheevii, leaf rust resistance, durum wheat, bread wheat

Abstracts, The Canadian Phytopathological Society, annual meeting, Winnipeg, Manitoba, July 1997

Abstracts, The Canadian Phytopathological Society, annual meeting, Winnipeg, Manitoba, July 1997

Inheritance of Leaf Rust Resistance in Wheat Cultivars Grandin and CDC Teal.

The hard red spring wheat cultivars Grandin and CDC Teal were genetically examined to determine the number and identity of the leaf rust resistance genes present in both wheats. The two cultivars were crossed with the leaf rust susceptible cultivar Thatcher, and the F1 plants were backcrossed to Thatcher. Fifty-four and 80 BC1F1 plants derived respectively from Grandin and CDC Teal were selfed to produce BC1F2 families. The BC1F2 families were tested as seedlings with isolates of Puccinia recondita f. sp. tritici that differed for virulence to specific leaf rust resistance genes. The BC1F2 families were also tested in the adult-plant stage in field rust nursery tests. Segregation of BC1F2 families in the seedling tests indicated that Grandin had resistance genes Lr2a, Lr3, and Lr10, and was heterogeneous for Lr16. CDC Teal was shown to have the seedling leaf rust gene Lr1. In field rust nursery tests, both Grandin and CDC Teal were shown to have adult-plant resistance genes Lr13 and Lr34. Additional leaf rust resistance genes that condition effective field resistance should be incorporated into hard red spring wheat cultivars to diversify the leaf rust resistance in this wheat class.

New Leaf Rust Resistance Genes in Barley and Their Allelic and Linkage Relationships with OtherRphGenes

The inheritance of leaf rust resistance was investigated in four barley accessions (PI 531840, PI 531841, PI 531849, and PI 584760) that were resistant to isolates of Puccinia hordei with wide virulence combinations. Crosses were made between the resistant barley lines and barley lines with genes Rph1 to Rph12 (except for Rph8) to determine the allelic and linkage relationships with known Rph genes. F 2 populations were evaluated for leaf rust reaction at the seedling stage. An incompletely dominant gene was identified in accessions PI 531841 and PI 584760, and a completely dominant gene was identified in PI 531849. The resistance gene in PI 531841 is an allele at the Rph2 locus or a closely linked locus. This gene also is present in accession PI 531840. A linkage was detected between this gene and Rph5 with recombination fractions of 33.8 ± 3.8 and 17.0 ± 3.5%, respectively, in crosses of 'Magnif' with PI 531841 and PI 531840. The Rph genes in PI 531849 and PI 584760 were not allelic at any of the previously reported Rph loci. Locus symbols Rph13 and Rph14 are recommended for the leaf rust resistance loci in PI 531849 and PI 584760, respectively. A linkage was detected between Rph13 and Rph9 with a recombination fraction of 30.4 ± 4.5%.

Inheritance of Seedling and Adult Plant Resistance to Leaf Rust in Wheat Cultivars Ciano 79 and Papago 86

Wheat (Triticum aetivum) cultivars Ciano 79 and Papago 86 have maintained high levels of resistance to leaf rust, caused by Puccinia recondita f. sp. tritici, since their release during 1979 and 1986, respectively, in leaf rust-prone northwestern Mexico. Because inheritance of leaf rust resistance for these cultivars is unknown, Ciano 79 and Papago 86 were intercrossed, crossed with the susceptible cultivar Sonora 64, and crossed with the adult plant resistant cultivar Frontana to evaluate the resistance relationship. Inheritance studies were conducted in seedling and/or adult plant growth stages using the parents, F 1 plants, F 2 populations, and F 3 and F 5 lines. The resistance to P.r. tritici pathotype TCB/TD in seedlings of Ciano 79 and Papago 86 was conferred by a single gene, Lr16. When present alone, Lr16 confers only moderate resistance in adult plants to the same pathotype. The adult plant resistances of both cultivars were based on the additive interaction between gene Lr16 and a minimum of two other slow-rusting genes. Besides Lr16, one of the two slow-rusting genes was also common in Ciano 79 and Papago 86. The adult plant resistance genes in these cultivars differed from the resistance genes in Frontana

Genetics of leaf-rust resistance in three spelt wheats

The inheritance of leaf-rust resistance was studied in three accessions of spelt wheat (Triticum aestivum ssp. spelta L.). Accession 7831 has a gene for seedling resistance to leaf rust that is linked with Lr33 (5.4 ± 1.05%), which is known to he on the long arm of chromosome 1B. This gene, which was either recessive or partially dominant, is designated Lr44, and because of its field reaction, should be useful in breeding rust-resistant wheats. Accession 7839 may also have this gene and an additional gene that in the seedling stage conditioned a type 2 infection to many races but little field resistance. Accessions 7831, 7839 and 7825 also have possibly in common a gene for adult-plant resistance. This gene, which did not give a high level of field resistance, was independent of Lr12, Lr13, Lr22, Lr34 and Lr35, other genes for adult-plant resistance. Key words:Triticum, wheat, leaf-rust resistance

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

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.

Inheritance of Leaf Rust Resistance in Wheat Cultivars Morocco and Little Club

Wheat cultivars Morocco and Little Club were considered to lack resistance genes to the leaf rust pathogen, Puccinia recondita f. sp. tritici, until several hundred cultures avirulent to one or both were obtained in a worldwide survey conducted by the Cereal Rust Laboratory, St. Paul, Minnesota. These cultures were obtained from many countries and were most commonly isolated from durum wheat. Two of these cultures are 89BGR4136-3, avirulent to Morocco, and 87ETH40904, virulent to some durum cultivars but avirulent to all but a few bread wheat cultivars. Progeny of a cross of two bread wheat cultivars Morocco/Little Club generally reported as susceptible to wheat leaf rust were evaluated