Displaying 1 - 10 of 40
Malika', a hard red spring wheat (Triticum aestivum L.) cultivar developed using doubled haploid technology by the Institut National de la Recherche Agronomique (INRA), Morocco, and tested as 06DHBW48, was approved for release in 2016 by the Office National de S?curit? Sanitaire des Produits Alimentaires (ONSSA), Morocco. Malika was selected from the doubled haploids derived from the cross 'Achtar3*//'Kanz'/Ks85-8-4). Achtar and Kanz are Moroccan varieties originating from segregating populations from CIMMYT. Achtar and Kanz are a well adapted to Moroccan conditions but susceptible to the Hessian fly, yellow rusts and some races of leaf rust. 'Achtar' was crossed with it in order to incorporate the Hessian fly resistance, yellow rust resistance and leaf rust resistance and 'Achtar' was crossed with Kanz/Ks85-8-4 having resistance to Hessian fly, yellow rust and leaf rust. Backcrossed 3 times with 'Achtar', and selected lines having resistance to the Hessian fly, yellow rust and leaf rust from the population derived from each backcross. Finally the selected the resistant line was used develop doubled haploids. The doubled haploid lines produced were tested in the laboratory and field for Hessian fly and the rust resistance. The resistant lines were incorporated in the multi-local yield trials and three promising lines with the resistance to Hessian fly, yellow rust and leaf rust and better yield and quality were submitted for registration in the official catalog in 2014. After 2 years of testing (years 2014-15 and 2015-16), one line (06DHBW48) was accepted for the registration and designated as 'Malika'. 'Malika' is a semi-dwarf variety, well adapted to semi-arid regions, early maturing, high yielding, tolerant to drought and resistant to Hessian fly, leaf rust and yellow rust.
The Lr34/Yr18/Sr57/Pm38/Ltn1 multi-resistance locus has been deployed and remained effective in wheat cultivars for more than 100 years. The durability and pleiotropic nature makes Lr34 a unique and highly valuable resource for rust resistance breeding. Despite its functional annotation as an ABC transporter, the mode of action is unknown. Considering this, we aimed to decipher molecular factors and signaling components essential for Lr34 function using RNA-seq of Chara resistant (Lr34) and Chara mutant (heavy ion irradiation, HII) susceptible wheat lines. Screening of Chara and Chara HII lines with Lr34-specific markers confirmed the integrity of Lr34 in both lines; however, phenotyping confirmed rust and powdery mildew susceptibility in the Chara HII lines. Plants were grown under controlled conditions and infected with Puccinia triticina pathotype 76-1,3,5,7,9,10,12,13+Lr37 at the flag leaf stage. Flag leaves were sampled at 0, 24, 48, 72, 96 and 168 hours post inoculation (hpi) from mock and infected plants. Based on real-time PCR analysis of basal defense genes and the Lr34 gene, we selected 72 hpi for RNA-seq with four biological replicates per condition. The samples were sequenced on an Illumina Hiseq 4000 at the Beijing Genomics Institute, China. A total of 9.0 Gb of sequence (2.25 Gb/library) from 16 libraries for four conditions was obtained. Differential expression analysis was performed using the Tuxedo analysis pipeline with standard parameters. Analysis revealed deletion of DNA fragments with collinear gene order on chromosomes 1A, 2D, 5A, 5B, 5D and 7D of Chara HII mutants. To determine the significance of the deletions we performed bulk segregant analyses on segregating F2 populations of Chara ? Chara HII crosses. Analyses revealed key genomic regions associated with Lr34-functional resistance and we are in the process of validating candidate genes using qPCR.
A total of 41 bread wheat (Triticum aestivum L.) varieties have been released so far in Nepal since 1960. Farmers have been gradually adopting newly released varieties due to disease and lodging resistance, better yield performance and good taste. In Nepal, wheat area coverage, production and productivity have been increased by almost seven, sixteen and two folds, respectively in the last 56 years. Performance of varieties varies from one region to another. Yellow rust is the major problems in hills while leaf rust is the primary issue on the plains. Stem rust is sporadic in localized areas of Nepal. Wheat research program in Nepal has released 9 wheat varieties resistant to Ug99 namely Vijaya, Tilottama, Banganga, Gaura, Dhaulagiri, Danphe, Sworgadwari, Munal and Chyakhura. Vijay, Tilottama and Banganga are also resistant to leaf rust while, Dhaulagiri, Danphe, Sworgadwari, Munal and Chyakhura are resistant to yellow rust. Since the release of Vijay, the first Ug99 resistant variety in Nepal during 2010, source seed production of rust resistant varieties has been increasing significantly each year with present coverage under these varieties being around 40%. WK 1204 has been occupied 35% area in hills of Nepal. Seed production and distribution of such high yielding disease resistant varieties through public-private partnership is leading to quality seed supply for varietal diversity and better food security in the country.
Wheat varieties with single effective gene for leaf rust resistance often quickly become susceptible because of multiplication of virulent Puccinia triticina genotypes. One of the methods to elongate term of effectiveness is to combine two genes in host genotype. To note, it is impossible to distinguish phenotypically plants or families having one or two genes in hybrid populations; the only method is to use PCR producing DNA markers linked to each gene for resistance. It is not convenient when necessary to analyze thousands plants or especially families of crosses between carriers of certain genes. At inoculation of wheat seedlings having Lr 9, 19, 24, 47, 29 and Sp with rust population from North-West region of Russian Federation all of them were absolutely resistant, so these genes may be considered to be effective in this region. Rust population was multiplied on cv. Leningradka leaf segments placed on cotton wool wetted with solution of maleic acid hidrazide (10 mg/l) + potassium chloride (0.48 g/l) +monosubstituted sodium phosphate (0.66 g/l) and used to infect seedling of the lines constantly poured with the solution. Rare pustules were recorded on each line. Isolates from the line were combined, multiplied and used to infect the lines set. Interaction specificity was shown for carriers of certain genes for resistance and inoculums. We propose to infect seedlings of hybrid wheat populations with mixtures of isolates virulent to first gene and those virulent to second one at use of above-mentioned method to multiply rust and grow plants. Seedlings resistant to that inoculum have both genes for resistance. If we have F3 or later families it is possible to use original population without selection of virulent isolates; in this case the method allowed removing progenies of heterozygous plants. With this approach we developed lines possessing combinations of Lr9+Lr24 and Lr9+Lr47 genes
Wheat plays a vital role in multifaceted farming system of Pakistan. Like other many other countries, Pakistan's sustainable wheat production is also continuously threatened by a number of biotic and abiotic stresses. Among the biotic stresses, three rust diseases of wheat have been the most devastating. Stem rust was effectively controlled with adoption of the semi-dwarf spring wheats of the Green Revolution. However, the threat of the evolution of Ug99 race of stem rust in East Africa and its migration to Iran cannot be neglected. The Chance of of Ug99 migrating from Iran into Pakistan, coupled with the presence of dangerous new races of stripe and leaf rusts invites enormous efforts for development of rust resistant varieties for sustainable production of the wheat in the country. In this regard the Wheat Program, NARC, Pakistan initiated an intensive breeding program with financial and technical support of USDA and CIMMYT. Diverse sources of resistance to the three rusts particularly to the stem rust race Ug99 were introduced from CIMMYT. Through the rigorous selection procedure, four rusts resistant wheat varieties (NARC 2011, Pakistan 2013, Zincol 2016 and Borlaug 2016) have been released. These varieties are also resistant to Ug99. The varieties i.e. NARC 2011, Borlaug 2016 and Zincol 2016 are performing well in irrigated areas whereas Pakistan 2013 is suitable for rainfed conditions. The variety Zincol 2016 has high Zn content (35 ppm) in grain as compared to national standard check variety (25 ppm). These varieties are not only higher yielding but also possess good grain quality and other desirable traits. A considerable quantity of seed of the varieties is already present in the national seed system and will reduce the risk of Ug99 threat.
Leaf rust is an important worldwide disease on wheat caused by the fungus Puccinia triticina. Great infections on durum wheat occurred in Southern Spain in the 2000s but diminished in recent years due to deployment of resistant varieties and application of fungicides by farmers. A leaf rust survey was carried out from the 2009-15 period to monitor the virulence spectrum of the prevailing pathotypes. A total of 84 leaf rust isolates were collected on durum wheat fields. From those, single culture were obtained and used to inoculate a set of 27 differential isolines of the susceptible variety Thatcher. In addition 8 durum varieties with known Lr genes were also included.
The main highlight is that the resistance conferred by the popular Lr14a gene was broke up in 2013, but since then virulence to this gene is not widespread. In total, 23% of the isolates were virulent to the lines containing Lr14a. Lr1, Lr3, Lr3bg, Lr16, Lr24, Lr26, and Lr28 are very effective. Lines carrying Lr2c, Lr10, Lr14b, Lr20, Lr23, and LrB displayed susceptibility to most isolates. The durum varieties Jupare (Lr27+Lr31), Guayacan (Lr61), Storlom (Lr3+) and Camayo (LrCam) are also resistant against all isolates tested. Diversification of Lr genes is needed in the coming varieties to delay the appearance of new virulent races.
Leaf rust is one of the major diseases of wheat in Bangladesh. The farmer fields and trial sites were regularly surveyed for rust assessment from 2010-2011 to 2016-2017 wheat growing seasons. Disease severity was recorded following BGRI protocols. Percentage of fields infected with leaf rust and the levels of disease severity varied with genotype, year, planting time and survey sites. Timely planted wheat either escaped or had less disease compared to late planted crop. Among our cultivated varieties, Shatabdi was either free from infection or exhibited only trace severity with resistant reaction. Variety Saurav, Bijoy, BARI Gom 27 , BARI Gom 28 , BARI Gom-29 and BARI Gom-30 were consistently free from leaf rust infection. BARI Gom 25 and BARI Gom 26 showed low to moderate disease levels with MRMS-MSS reactions, while the variety Prodip demonstrated moderate to high disease severity with susceptible response and it needs to be replaced by resistant variety to sustain wheat productivity.
Leaf rust (LR) is an important wheat disease and deployment of resistant cultivars is the most viable strategy to minimise yield losses. We evaluated a diversity panel of 295 bread wheat accessions from the N. I. Vavilov Institute of Plant Genetic Resources (VIR), St Petersburg, Russia for LR response and performed genome-wide association studies (GWAS) using 10,748 polymorphic DArT-seq markers. The diversity panel was evaluated at the seedling and adult plant growth stages using three prevalent Australian P. triticina pathotypes. GWAS applied to 11 phenotypic data sets identified a total of 52 significant marker-trait associations representing 31 quantitative trait loci (QTL). Among them, 29 QTL were associated with adult plant resistance (APR). Of the 31 QTL, 13 were considered potentially new loci, whereas 4 co-located with previously catalogued Lr genes and 14 aligned to regions reported in other GWAS and genomic prediction studies. One seedling LR resistance QTL located on chromosome 3A showed pronounced levels of linkage disequilibrium among markers (r2 = 0.7), indicative of a high allelic fixation. Subsequent haplotype analysis for this region found 7 haplotype variants, of which 2 were strongly associated with LR resistance at the seedling stage. Similarly, analysis of an APR QTL on chromosome 7B revealed 22 variants, of which 4 were associated with resistance at the adult-plant stage. Most of the lines in the diversity panel carried 10 or more combined resistance-associated marker alleles, highlighting the potential of allele stacking for long-lasting resistance.
Leaf rust disease, caused by the fungal pathogen Puccinia tritcina, is the most destructive foliar disease of wheat worldwide. Gene combination of Lr37/Yr17/Sr38 has been used in Georgia (GA) to prevent the loss from leaf rust; however, with the emergence of new virulent races, these genes have lost their effectiveness. 'AGS 2000' and 'Pioneer 26R61' are the most common soft red winter wheat (SRWW) cultivars in Southeastern US, and have been used as good sources of resistance to leaf and stripe rusts, and powdery mildew. To characterize the genetic basic of resistance of AGS 2000, a mapping population of 178 recombinant inbred lines (RIL) has been developed from a cross with Pioneer 26R61. This population was genotyped using a combination of SSR, DArT, and SNP markers, and a total of 2734 markers covering the entire genome were used for the construction of genetic map. Phenotypic evaluation of parents and RIL population was conducted at the seedling stage using a virulent GA leaf rust race. QTL mapping revealed a major QTL on chromosome 2BL, explaining about 20% of total phenotypic variation in AGS 2000. Additionally, a minor QTL was also detected on chromosome 5B. QTL on 2BL was identified as a novel gene, and can be used in marker-assisted selection for leaf rust resistance.
Leaf rust disease, caused by the fungal pathogen Puccinia triticina, is a major biotic constraint of wheat production worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to control and reduce losses caused by this disease. More than 70 leaf rust resistance genes have been identified and mapped to specific chromosomes; however, continuous evolution of new leaf rust races requires constant search for new sources of resistance with novel QTL/genes. The objectives of this study were to identify sources of resistance, and to map genomic loci associated with leaf rust resistance using genome wide association study (GWAS) approach. Phenotypic evaluation of 297 spring wheat genotypes against a prevalent race of leaf rust in Georgia revealed that most of the genotypes were susceptible, and only 24 genotypes were found resistant. Furthermore, GWAS detected 10 markers on chromosomes 2A, 2B, 6A, 7A, and 7B significantly associated with leaf rust resistance. A marker on chromosome 7AS was identified revealing a novel genomic region associated with leaf rust resistance. The new identified sources of resistance and QTL could be used in wheat breeding programs to improve leaf rust resistance.