Microsatellite Markers Associated with Spot Blotch Resistance in Spring Wheat

Spot blotch, caused by Cochliobolus sativus, is a serious wheat (Triticum aestivum L.) disease in the warm areas of South Asia. Breeding for resistance in the past 15 years has produced limited progress, and newly developed wheat cultivars suffer considerable yield reductions under spot blotch epidemics in the region. Resistance is often controlled by multiple genes with additive effects. Marker‐assisted selection, in combination with field selection, could accelerate the identification of progeny with multiple genes for resistance early in the breeding process. A study was conducted to determine microsatellite markers associated with resistance in the F₇ progeny from a cross between the spot blotch‐susceptible Sonalika and resistant G162 wheat genotypes. A parental survey using 171 simple sequence repeats (SSR) primer sets and spread over 21 chromosomes of wheat identified 52% polymorphic loci. However, only 15 polymorphic markers showed association with two bulks, one each of progeny with low and with high spot blotch severity. The detailed analysis indicated that progeny lines with low spot blotch severity could be separated from those with high severity using three SSR markers located on three wheat chromosomes. The findings may be useful in developing a marker‐assisted selection strategy for spot blotch resistance in wheat.     

Genetic Improvement and Crop Management Strategies to Minimize Yield Losses in Warm Non-traditional Wheat Growing Areas due to Spot Blotch Pathogen Cochliobolus sativus

Spot blotch caused by Cochliobolus sativus emerged as a major threat to wheat production in the warmer non-traditional wheat growing areas in the late 1980s. This foliar disease causes significant yield losses annually (15–20% on average in South Asia) endangering the livelihoods of millions of small farmers. Effective measures in the field are needed to mitigate the impact of spot blotch on food security in affected areas. This review summarizes the global knowledge on genetic improvement and crop management strategies to minimize yield losses based on latest field research. Recent studies have shown that spot blotch severity is highly influenced by stress factors affecting crop physiology which in turn affects host tolerance and resistance to the pathogen. Soil nutrient and water stress aggravate spot blotch-induced grain yield losses. Heat stress which is gradually increasing in Asia causes higher levels of disease damage. Genetic improvement is the cornerstone of a sustainable control of spot blotch in all affected regions. Resistance is essentially based on Chinese and South American sources and inter-specific crosses with broadly adapted semi-dwarf germplasm. A list of genotypes consistently reported in the last 10 years to harbor at least partial resistance to spot blotch, along with their inheritance of resistance, has been compiled to help breeding programmes. As the fungus is aggressive under conditions of high relative humidity and heat which in turn influences plant susceptibility, a synthesis of the different tools for scoring disease severity is given. Because resistance is incomplete, the ultimate goal is the accumulation of minor genes of resistance in adapted high yielding genotypes. This paper shows how the use of resistant varieties, timely seeding, adequate fertilization, crop rotation, and the judicious use of fungicides can be part of an integrated management strategy for controlling yield losses due to spot blotch.     

Wheat Resistance to Spot Blotch Potentiated by Silicon

Spot blotch, caused by the fungus Bipolaris sorokiniana, is one of the most important diseases on wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars BR‐18 and BRS‐208 were grown in plastic pots containing Si‐deficient soil amended with either calcium silicate (+Si) or calcium carbonate (?Si). The content of Si in leaf tissue was significantly increased by 90.5% for the +Si treatment. There was no significant difference between Si treatments for calcium content, so variations in Si accounted for differences in the level of resistance to spot blotch. The incubation period was significantly increased by 40% for the +Si treatment. The area under spot blotch progress curve, number of lesions per cm² of leaf area, and real disease severity significantly decreased by 62, 36 and 43.5% in +Si treatment. There was no significant effect of Si on lesion size. The role played by total soluble phenolics in the increased resistance to spot blotch of plants from both cultivars supplied with Si was not clear. Plants from cultivar BR‐18 supplied with Si showed the highest values for concentration of lignin‐thioglycolic acid derivatives during the most advanced stages of fungus infection. Chitinase activity was high at the most advanced stages of fungus infection on leaves from both cultivars supplied with Si and may have had an effect on fungus growth based on the reduction of the components of resistance evaluated. Peroxidase activity was found to be high only at 96 h after inoculation of both cultivars supplied with Si. Polyphenoloxidase activity had no apparent effect on resistance regardless of Si treatments. Results revealed that supplying Si to wheat plants can increase resistance against spot blotch.     

QTL for spot blotch resistance in bread wheat line Saar co-locate to the biotrophic disease resistance loci Lr34 and Lr46

Spot blotch caused by Bipolaris sorokiniana is a major disease of wheat in warm and humid wheat growing regions of the world including south Asian countries such as India, Nepal and Bangladesh. The CIMMYT bread wheat line Saar which carries the leaf tip necrosis (LTN)-associated rust resistance genes Lr34 and Lr46 has exhibited a low level of spot blotch disease in field trials conducted in Asia and South America. One hundred and fourteen recombinant inbred lines (RILs) of Avocet (Susceptible) × Saar, were evaluated along with parents in two dates of sowing in India for 3 years (2007–2008 to 2009–2010) to identify quantitative trait loci (QTL) associated with spot blotch resistance, and to determine the potential association of Lr34 and Lr46 with resistance to this disease. Lr34 was found to constitute the main locus for spot blotch resistance, and explained as much as 55 % of the phenotypic variation in the mean disease data across the six environments. Based on the large effect, the spot blotch resistance at this locus has been given the gene designation Sb1. Two further, minor QTL were detected in the sub-population of RILs not containing Lr34. The first of these was located about 40 cM distal to Lr34 on 7DS, and the other corresponded to Lr46 on 1BL. A major implication for wheat breeding is that Lr34 and Lr46, which are widely used in wheat breeding to improve resistance to rust diseases and powdery mildew, also have a beneficial effect on spot blotch.     

Genome-wide association mapping reveals genetic architecture of durable spot blotch resistance in US barley breeding germplasm

Spot blotch, an economically important disease of both barley and wheat, is caused by Cochliobolus sativus (anamorph: Bipolaris sorokiniana). The disease has been reported in many regions of the world, but is particularly severe on barley in the Upper Midwest region of the USA and adjacent areas of Canada. For over 50 years, spot blotch has been effectively controlled through the deployment of durable resistance in six-rowed malting cultivars. To characterize loci conferring spot blotch resistance in US barley germplasm, we employed an association mapping approach using 3,840 breeding lines and cultivars. Three quantitative trait loci (QTL), Rcs-qtl-1H-11_10764, Rcs-qtl-3H-11_10565 and Rcs-qtl-7H-11_20162, were found to confer both seedling and adult plant resistance. Together, these three QTL comprise the Midwest Six-rowed Durable Resistant Haplotype (MSDRH), which is present in all Midwest six-rowed cultivars released since the 1960s. Each QTL alone only partially reduced disease levels, but combining all three together reduced the seedling infection response and adult plant disease severity by 47 and 83 %, respectively. The identified MSDRH will be valuable for marker-assisted selection of breeding lines to deploy spot blotch resistance and can also be incorporated into genomic selection as one of the disease resistance traits.     

Mapping of resistance to spot blotch disease caused by Bipolaris sorokiniana in spring wheat

Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat in warm and humid wheat growing regions of the world. The development of disease resistant cultivars is considered as the most effective control strategy for spot blotch. An intervarietal mapping population in the form of recombinant inbred lines (RILs) was developed from a cross ‘Yangmai 6’ (a Chinese source of resistance) × ‘Sonalika’ (a spot blotch susceptible cultivar). The 139 single seed descent (SSD) derived F₆, F₇, F₈ lines of ‘Yangmai 6’ × ‘Sonalika’ were evaluated for resistance to spot blotch in three blocks in each of the 3 years. Joint and/or single year analysis by composite interval mapping (CIM) and likelihood of odd ratio (LOD) >2.2, identified four quantitative trait loci (QTL) on the chromosomes 2AL, 2BS, 5BL and 6DL. These QTLs were designated as QSb.bhu-2A, QSb.bhu-2B, QSb.bhu-5B and QSb.bhu-6D, respectively. A total of 63.10% of phenotypic variation was explained by these QTLs based on the mean over years. Two QTLs on chromosomes 2B and 5B with major effects were consistent over 3 years. All QTL alleles for resistance were derived from the resistant parent ‘Yangmai 6’.     

Phenotyping at hot spots and tagging of QTLs conferring spot blotch resistance in bread wheat

Spot blotch is a major foliar disease of wheat caused by Bipolaris sorokiniana in warm and humid environments of the world including South Asian countries. In India, it has a larger impact in Indo-Gangetic plains of the country. Therefore, the present study was undertaken to phenotype a mapping population at different hot spots of India and to detect quantitative trait loci (QTL) for resistance to spot blotch in wheat. For this study, 209 single seed descent (SSD) derived F₈, F₉, F₁₀ recombinant inbred lines (RILs) of the cross ‘Sonalika’ (an Indian susceptible cultivar)/‘BH 1146’ (a Brazilian resistant cultivar) were assessed for spot blotch resistance at two hot spot locations (Coochbehar and Kalyani) for three years and for two years under controlled conditions in the polyhouse (Karnal). The population showed large variation in spot blotch reaction for disease severity in all the environments indicating polygenic nature of the disease. Microsatellite markers were used to create the linkage maps. Joint and/or individual year analysis by composite interval mapping (CIM) and likelihood of odds ratio (LOD) >2.1, detected two consistent QTLs mapped on chromosome 7BL and 7DL and these explained phenotypic variation of 11.4 percent and 9.5 percent over the years and locations, respectively. The resistance at these loci was contributed by the parent ‘BH 1146’ and shown to be independent of plant height and earliness. Besides, association of some agro-morphological traits has also been observed with percent disease severity. These identified genomic regions may be used in future wheat breeding programs through marker assisted selection for developing spot blotch resistant cultivars.     

Sources of resistance and susceptibility to Septoria tritici blotch of wheat

An association genetics analysis was conducted to investigate the genetics of resistance to Septoria tritici blotch, caused by the fungus Zymoseptoria tritici (alternatively Mycosphaerella graminicola), in cultivars and breeding lines of wheat (Triticum aestivum) used in the UK between 1860 and 2000. The population was tested with Diversity Array Technology (DArT) and simple‐sequence repeat (SSR or microsatellite) markers. The lines formed a single population with no evidence for subdivision, because there were several common ancestors of large parts of the pedigree. Quantitative trait loci (QTLs) controlling Septoria resistance were postulated on 11 chromosomes, but 38% of variation was not explained by the identified QTLs. Calculation of best linear unbiased predictions (BLUPs) identified lineages of spring and winter wheat carrying different alleles for resistance and susceptibility. Abundant variation in Septoria resistance may be exploited by crossing well‐adapted cultivars in different lineages to achieve transgressive segregation and thus breed for potentially durable quantitative resistance, whereas phenotypic selection for polygenic quantitative resistance should be effective in breeding cultivars with increased resistance. The most potent allele reducing susceptibility to Septoria, on chromosome arm 6AL, was associated with reduced leaf size. Genes which increase susceptibility to Septoria may have been introduced inadvertently into UK wheat breeding programmes from cultivars used to increase yield, rust resistance and eyespot resistance between the 1950s and 1980s. This indicates the need to consider trade‐offs in plant breeding when numerous traits are important and to be cautious about the use of non‐adapted germplasm.     

Mapping quantitative trait loci associated with spot blotch and net blotch resistance in a doubled-haploid barley population

Spot blotch and net blotch are important foliar barley (Hordeum vulgare L.) diseases in Canada and elsewhere. These diseases result in significant yield reduction and, more importantly, loss of grain quality, downgrading barley from malt to feed. Combining resistance to these diseases is a breeding priority but is a significant challenge using conventional breeding methodology. In the present investigation, an evaluation of the inheritance of resistance to spot and net blotch was conducted in a doubled-haploid barley population from the cross CDC Bold (susceptible)?×?TR251 (resistant). The population was screened at the seedling stage in the Phytotron and at the adult-plant stage in the field for several years. Chi-squared analysis indicated one- to four-gene segregation depending on disease, isolate, plant development stage, location and year. A major seedling and adult-plant resistance quantitative trait locus (QTL), designated QRpt6, was re-confirmed for net-form net blotch resistance, explaining 32?C61% of phenotypic variation in different experiments. Additional QTL for seedling and adult-plant resistance to net blotch were identified. For spot blotch resistance, a major seedling resistance QTL (QRcss1) was detected on chromosome 1H for isolate WRS1909, explaining 79% of the phenotypic variation. A highly significant QTL on 3H (QRcs3) was identified for seedling resistance to isolate WRS1908 and adult-plant resistance at Brandon, MB, Canada in 2008. The identification of QTL at only one location or from 1?year suggests spot blotch resistance is complex and highly influenced by the environment. Efforts are being made to combine spot and net blotch resistance in elite barley lines using molecular marker-assisted selection.     

Quantitative trait loci for resistance to spot blotch caused by Bipolarissorokiniana in wheat (T.aestivum L.) lines ‘Ning 8201’ and ‘Chirya 3’

Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat in warm and humid wheat growing regions of the world. To identify quantitative trait loci (QTLs) for spot blotch resistance, two mapping populations were developed by making the crosses between common susceptible cultivar ‘Sonalika’ with the resistant breeding lines ‘Ning 8201’ and ‘Chirya 3’. Single seed descent derived F₆, F₇, F₈ lines of the first cross ‘Ning 8201’ × ‘Sonalika’ were evaluated for resistance to spot blotch in three blocks in each of the 3 years. After screening of 388 pairs of simple sequence repeat primers between the two parents, 119 polymorphic markers were used to genotype the mapping population. Four QTLs were identified on the chromosomes 2AS, 2BS, 5BL and 7DS and explained 62.9% of phenotypic variation in a simultaneous fit. The QTL on chromosome 2A was detected only in 1 year and explained 22.7% of phenotypic variation. In the second cross (‘Chirya 3’ × ‘Sonalika’), F₇ and F₈ population were evaluated in three blocks in each of the 2 years. In this population, five QTLs were identified on chromosomes 2BS, 2DS, 3BS, 7BS and 7DS. The QTLs identified in the ‘Chirya 3’ × ‘Sonalika’ population explained 43.4% of phenotypic variation in a simultaneous fit. The alleles for reduced disease severity in both the populations were derived from the respective resistant parent. The QTLs QSb.bhu-2B and QSb.bhu-7D from both populations were placed in the same deletion bins, 2BS1-0.53-0.75 and 7DS5-0.36-0.61, respectively. The closely linked markers Xgwm148 to the QTL on chromosome 2B and Xgwm111 to the QTL on chromosome 7D are potentially diagnostic markers for spot blotch resistance.     

Identification of resistance source in wheat germplasm against spot blotch disease caused by Bipolaris sorokiniana

Four hundred and twenty-two spring wheat germplasm (Triticum aestivum L.) lines belonging to Indian, CIMMYT and Chinese wheat programme were evaluated for their tolerance against natural epiphytotic conditions of spot blotch caused by Bipolaris sorokiniana at the hot spot location, Pusa, Bihar, India. Of the 422 entries screened, none of the genotype showed immunity to the disease, whereas 52 were resistant, 180 moderately susceptible, 171 susceptible and 19 highly susceptible. Indian germplasm lines tended to be more susceptible than lines originated from CIMMYT and China. Chirya 3, Chirya 7 and Mayoor from CIMMYT showed high degree of resistance to the disease both under field and polyhouse conditions. On the basis of the disease severity under field conditions, 20 promising resistant genotypes and 10 highly susceptible lines were isolated for further testing under artificial epiphytotic conditions in polyhouse for genetic analysis and their potential for spot blotch resistance breeding.     

Association mapping of spot blotch resistance in wild barley

Spot blotch, caused by Cochliobolus sativus, is an important foliar disease of barley. The disease has been controlled for over 40 years through the deployment of cultivars with durable resistance derived from the line NDB112. Pathotypes of C. sativus with virulence for the NDB112 resistance have been detected in Canada; thus, many commercial cultivars are vulnerable to spot blotch epidemics. To increase the diversity of spot blotch resistance in cultivated barley, we evaluated 318 diverse wild barley accessions comprising the Wild Barley Diversity Collection (WBDC) for reaction to C. sativus at the seedling stage and utilized an association mapping (AM) approach to identify and map resistance loci. A high frequency of resistance was found in the WBDC as 95% (302/318) of the accessions exhibited low infection responses. The WBDC was genotyped with 558 Diversity Array Technology (DArT^®) and 2,878 single nucleotide polymorphism (SNP) markers and subjected to structure analysis before running the AM procedure. Thirteen QTL for spot blotch resistance were identified with DArT and SNP markers. These QTL were found on chromosomes 1H, 2H, 3H, 5H, and 7H and explained from 2.3 to 3.9% of the phenotypic variance. Nearly half of the identified QTL mapped to chromosome bins where spot blotch resistance loci were previously reported, offering some validation for the AM approach. The other QTL mapped to unique genomic regions and may represent new spot blotch resistance loci. This study demonstrates that AM is an effective technique for identifying and mapping QTL for disease resistance in a wild crop progenitor.     

The Association Between Leaf Malondialdehyde and Lignin Content and Resistance to Spot Blotch in Wheat

Spot blotch (causative pathogen Bipolaris sorokiniana (Sacc.) Shoem) is a common disease of wheat in the Eastern Gangetic Plains region of India. The association of leaf malondialdehyde and lignin contents with the severity of spot blotch disease was studied using a correlation analysis based on a population of recombinant inbred lines bred from the cross cvs. Yangmai 6 (resistant) × Sonalika (susceptible). The material was field‐tested over two consecutive years and inoculated artificially with a highly virulent strain of the pathogen. Disease severity was assessed at three growth stages around and after anthesis. Leaf lignin content tended to be higher in the more resistant RILs, while the opposite was the case for leaf malondialdehyde content. Lesion size showed a positive correlation with disease severity and leaf malondialdehyde content, while disease severity and leaf lignin content were negatively correlated with one another, as were leaf malondialdehyde and leaf lignin content. Leaf malondialdehyde and/or leaf lignin content could be informative as markers for selection for higher levels of resistance against spot blotch in wheat.     

Mycosphaerella graminicola: from genomics to disease control

This Mycosphaerella graminicola pathogen profile covers recent advances in the knowledge of this ascomycete fungus and of the disease it causes, septoria tritici blotch of wheat. Research on this pathogen has accelerated since publication of a previous pathogen profile in this journal in 2002. Septoria tritici blotch continues to have high economic importance and widespread global impact on wheat production. Taxonomy: Mycosphaerella graminicola (Fuckel) J. Schröt. In Cohn (anamorph: Septoria tritici Roberge in Desmaz.). Kingdom Fungi, Phylum Ascomycota, Class Loculoascomycetes (filamentous ascomycetes), Order Dothideales, Genus Mycosphaerella, Species graminicola. Host range: Bread and durum wheat (Triticum aestivum L. and T. turgidum ssp. durum L.). Disease symptoms: Initially leaves develop a chlorotic flecking, which is followed by the development of necrotic lesions which contain brown–black pycnidia. Necrosis causes a reduction in photosynthetic capacity and therefore affects grain yield. Disease control: The disease is primarily controlled by a combination of resistant cultivars and fungicides. Rapid advances in disease control, especially in resistance breeding, are opening up new opportunities for the management of the disease. Useful websites: http://genome.jgi‐psf.org/Mycgr3/Mycgr3.home.html .     

Sources and donors of resistance to wheat spot blotch caused by Bipolaris sorokiniana Shoem. (Cochliobolus sativus Drechs. ex Dastur)

The resistance of wheat lines and cultivars from the Institute of Crop Breeding (Harbin, China) and synthetic, hexaploid wheat lines derived from T. durum and T. tauschii (CIMMYT) were screened for resistance to spot blotch Bipolaris sorokiniana Shoem. using field and laboratory tests. The highly and moderately resistant wheat samples were determined. The satisfactory coincidence of data obtained from evaluation of type reaction of seedlings and disease severity in adult plant stage was demonstrated. The genetics of resistance in Chinese lines Long 98-4554, Long 98-4546, Long mai 24, Long mai 23 and Canadian line 181-5 was studied using hybridological analysis. The resistance in these lines was inherited as quantitative traits and was conditioned by a few (one or two) genes. The absence of susceptible plants in F₂ in crosses of resistant lines Long 98-4554, Long 98-4546, Long mai 24 and 181-5 can testify to the presence of a common gene of resistance. Our data reveals the poor genetic diversity for spot blotch resistance in studying wheat genotypes.     

Changes in leaf gas exchange,chlorophyll a fluorescence and antioxidant metabolism within wheat leaves infected by Bipolaris sorokiniana

The photosynthetic performance (leaf gas exchange and chlorophyll a (Chla) fluorescence), activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX)] and the concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) in the flag leaves of plants from two wheat cultivars with contrasting levels of resistance to spot blotch was assessed. Spot blotch severity was significantly lower in plants from cv. BR‐18 compared to cv. Guamirim. Net carbon assimilation rate, stomatal conductance and concentrations of Chla, Chlab and carotenoids were significantly decreased from fungal infection. In contrast, internal CO₂ concentration was significantly increased from fungal infection in comparison to their non‐inoculated counterparts. Similarly, inoculation significantly reduced photochemical performance in the inoculated flag leaves in comparison to their non‐inoculated counterparts. However, plants from cv. BR‐18 were able to sustain greater functionality of the photosynthetic apparatus during fungal infection process compared to cv. Guamirim. The activities of SOD, POX, APX and CAT increased in inoculated flag leaves from both cultivars compared to non‐inoculated plants, and the highest increases were measured in cv. BR‐18. The greater activities of these enzymes were associated with a reduced H₂O₂ concentration in the inoculated flag leaves from cv. BR‐18, resulting, therefore, in a lower MDA concentration. Thus, a more efficient antioxidative system in flag leaves from cv. BR‐18 plays a pivotal role in removing the excess reactive oxygen species that were generated during the infection process of Bipolaris sorokiniana, therefore limiting cellular damage and largely preserving the photosynthetic efficiency of the infected flag leaves.     

Identification of molecular markers for resistance to Septoria nodorum blotch in durum wheat

The development of Septoria nodorum blotch-resistant cultivars has become a high priority objective for durum wheat breeding programs. Marker-assisted selection enables breeders to improve selection efficiency. In order to develop markers for resistance to Septoria nodorum blotch, a set of F₅ recombinant inbred lines, derived from the crosses Sceptre/3–6, Sceptre/S9–10 and Sceptre/S12–1, was developed based on the F₂-derived family method. Two RAPD markers, designated UBC521₆₅₀ and RC37₅₁₀, were detected by bulked segregant analysis and located approximately 15 and 13.1 centiMorgans (cM) from the resistance gene snbTM, respectively. A SCAR marker was also successfully developed for marker-assisted selection in breeding programs based on the sequence of the RAPD marker UBC521₆₅₀. This is the first report of DNA-based markers linked to resistance for Septoria nodorum blotch in durum wheat. Received: 8 March 2000 / Accepted: 25 June 2000     

Mapping resistance to spot blotch in a CIMMYT synthetic-derived bread wheat

Spot blotch, caused by Cochliobolus sativus, is an important foliar disease of wheat in warmer wheat-growing regions leading to significant reductions in grain yield and quality. Although inoculum levels can be reduced by planting disease-free seed, treatment of plants with fungicides and crop rotation, genetic resistance is likely to be a robust, economical and environmentally friendly tool in the control of spot blotch. The spot blotch resistant synthetic derivative ‘SYN1’ was developed from a cross between two resistance sources, Mayoor and the primary synthetic bread wheat Tksn1081/Ae. squarrosa (222) that are likely to form an important component of resistance in many elite CIMMYT bread wheats. In order to map the loci underlying the resistance of ‘SYN1’, a doubled-haploid population produced from a cross between ‘SYN1’ and the susceptible CIMMYT-derived variety Ocoroni-86 was evaluated in artificially inoculated field nurseries in the 2010–2011 and 2011–2012 crop seasons at CIMMYT’s research station in Agua Fría, Mexico. Disease assessment was performed on three or four occasions and subsequently area under disease progress curve (AUDPC) calculated. Genotyping was with genotyping by sequencing and simple sequence repeat markers. Using inclusive composite interval mapping, three genomic regions were found to have a significant effect on spot blotch AUDPC in each of the 2 years of trials with phenotypic variation explained by QSb.cim-1B of 8.5 %, 17.6 % by QSb.cim-3B and 12.3 % by QSb.cim-5A. The quantitative trait loci (QTL) mapping results showed that the favorable alleles of QSb.cim-1B, QSb.cim-3B and QSb.cim-5A were derived from the synthetic-derived bread wheat SYN1. Genotypes of the parents of SYN1 indicated that the favorable alleles at these three QTLs were all inherited from Mayoor.     

A review of wheat diseases—a field perspective

Wheat is one of the primary staple foods throughout the planet. Significant yield gains in wheat production over the past 40 years have resulted in a steady balance of supply versus demand. However, predicted global population growth rates and dietary changes mean that substantial yield gains over the next several decades will be needed to meet this escalating demand. A key component to meeting this challenge is better management of fungal incited diseases, which can be responsible for 15%–20% yield losses per annum. Prominent diseases of wheat that currently contribute to these losses include the rusts, blotches and head blight/scab. Other recently emerged or relatively unnoticed diseases, such as wheat blast and spot blotch, respectively, also threaten grain production. This review seeks to provide an overview of the impact, distribution and management strategies of these diseases. In addition, the biology of the pathogens and the molecular basis of their interaction with wheat are discussed.