Characterization, Identification and Evaluation of Wheat-Aegilops sharonensis Chromosome Derivatives

Aegilops sharonensis, a wild relative of wheat, harbors diverse disease and insect resistance genes, making it a potentially excellent gene source for wheat improvement. In this study, we characterized and evaluated six wheat-A. sharonensis derivatives, which included three disomic additions, one disomic substitution + monotelosomic addition and two disomic substitution + disomic additions. A total of 51 PLUG markers were developed and used to allocate the A. sharonensis chromosomes in each of the six derivatives to Triticeae homoeologous groups. A set of cytogenetic markers specific for A. sharonensis chromosomes was established based on FISH using oligonucleotides as probes. Molecular cytogenetic marker analysis confirmed that these lines were a CS-A. sharonensis 2Ssh disomic addition, a 4Ssh disomic addition, a 4Ssh (4D) substitution + 5SshL monotelosomic addition, a 6Ssh disomic addition, a 4Ssh (4D) substitution + 6Ssh disomic addition and a 4Ssh (4D) substitution + 7Ssh disomic addition line, respectively. Disease resistance investigations showed that chromosome 7Ssh of A. sharonensis might harbor a new powdery mildew resistance gene, and therefore it has potential for use as resistance source for wheat breeding.

Characterization of the Powdery Mildew Resistance Gene in Wheat Breeding Line KN0816 and its Evaluation in Marker-Assisted Selection

Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease seriously threatening yield and quality of common wheat (Triticum aestivum L., 2n=6x=42, AABBDD). Characterization of resistance genes against powdery mildew is useful in parental selection and for developing disease resistant cultivars. Chinese wheat breeding line KN0816 has superior agronomic performance and resistance to powdery mildew at all growth stages. Genetic analysis using populations of KN0816 crossed with different susceptible parents indicated that a single dominant gene, tentatively designated PmKN0816, conferred seedling resistance to different Bgt isolates. Using a bulked segregant analysis (BSA), PmKN0816 was mapped to the Pm6 interval on chromosome arm 2BL using polymorphic markers linked to the catalogued genes Pm6, Pm52, and Pm64, and flanked by markers CISSR02g-6 and CIT02g-2 both with genetic distances of 0.7 cM. Analysis of closely linked molecular markers indicated that the marker alleles of PmKN0816 differed from those of other powdery mildew resistance genes on 2BL, including Pm6, Pm33, Pm51, Pm64, and PmQ. Based on the genetic and physical locations and response pattern to different Bgt isolates, PmKN0816 is most likely a new powdery mildew resistance gene and confers effective resistance to all the 14 tested Bgt isolates. In view of the elite agronomic performance of KN0816 combined with the resistance, PmKN0816 is expected to become a valuable resistance gene in wheat breeding. To transfer PmKN0816 to different genetic backgrounds using marker-assisted selection (MAS), closely linked markers of PmKN0816 were evaluated and four of them (CIT02g-2, CISSR02g-6, CIT02g-10, and CIT02g-17) were confirmed to be applicable for MAS in different genetic backgrounds.

The Exocyst Complex Subunit EXO70E1-V From Haynaldia villosa Interacts With Wheat Powdery Mildew Resistance Gene CMPG1-V

EXO70 belongs to the exocyst complex subunit that plays a critical role in regulating plant cell polarity establishment and defense response. A previous study proved that the E3 ligase CMPG1-V from Haynaldia villosa, a diploid wheat relative, positively regulates the resistance to wheat powdery mildew (Pm), caused by fungus Blumeria graminis f.sp tritici (Bgt). In this study, a member of EXO70 superfamily named EXO70E1-V was isolated from H. villosa, and EXO70E1-V interacted with CMPG1-V were shown by yeast two-hybrid (Y2H), pull-down assay, bimolecular fluorescence complementation (BiFC) assay, and luciferase complementation imaging (LCI) assay. It is localized in various subcellular organs, i.e., plasma membrane (PM) and endoplasmic reticulum. Co-expression of EXO70E1-V and CMPG1-V showed dot-like structure fluorescence signals that were mainly in PM and nucleus. Expression of EXO70E1-V was relatively higher in leaf and was significantly induced by Bgt infection and exogenous application of hormones such as salicylic acid. Transient or stable overexpression of EXO70E1-V could not enhance/decrease the Pm resistance level, suggesting overexpression of EXO70E1-V alone has no impact on Pm resistance in wheat.

Correction to: Allocation of the oat powdery mildew resistance gene Pm3 to oat chromosome 1A

There were errors in Table 1 and Table S1 (in the supplementary material). Several cultivars were specified with incorrect gene statuses. The original article has been corrected (incl. the supplementary material).

Genetic Diversity Analysis and Validation of Microsatellite Markers Linked with Tolerance to Powdery Mildew Disease in Mungbean [Vigna radiata (L.) Wilczek]

Background: Mungbean [Vigna radiata (L.) Wilczek] is a self-pollinated diploid grain legume (2n=2x=22) crop and has a genome size of 560 Mb. The present study was concentrate to portray the nature and extent of genotypic variation exists among mungbean collections for a range of traits of potential agronomic and adaptive interests. Many diseases affect mungbean, causes the major constraint in the increasing production among which Powdery mildew disease caused by Erisyphepolygoni is economically significant because it reduces photosynthetic activity and physiological changes which results in 20-40 per cent reduction in yield. Some gene-specific marker were analysed and found associated with powdery mildew resistance in mungbean genotypes.Methods: The present investigation was carried out to evaluate thirty-one mungbean genotypes (including four checks) collected from the different parts of India. The genotypes were sown in an incomplete augmented bock design along with four checks varieties. viz. ‘Kamdev’, ‘OBBGG-52’, ‘IPM-02-14’ and ‘IPM-02-3’. All the mungbean genotypes were evaluated for different phenotypic traits and their tolerance to powdery mildew disease at two cropping seasons as well as at two different locations in Odisha. In this investigation, seven molecular markers viz., VrCSSTS1, VrCSSTS2, VrCSSSR3, CEDG191, MB-SSR238, CEDG166, CEDG282 were analysed.Result: SSR marker such as VrCSSSR and VrCSSTS linked with powdery mildew resistance gene were tested in different genotypes with known powdery mildew reaction and the results showed a consistent association of the marker in all the powdery mildew resistant genotypes and absent in all the powdery mildew susceptible genotypes. The results confirmed the validation of these markers with the powdery mildew resistance gene in different genetic backgrounds. Similarly, CEDG191, CEDG166, CEDG282 markers, reported to be linked to powdery mildew resistance, amplified the respective marker fragment of 100 to 300 bp in mungbean genotypes and were polymorphic. The above PCR-based and locus-specific markers could be employed for marker-assisted breeding (MAB) program as well as genotype conservation. These linked markers will boost the efficiency and precision of powdery mildew resistance breeding in mungbean.

Characterization of PmHHXM, a New Broad-spectrum Powdery Mildew Resistance Gene in Chinese Wheat Landrace Honghuaxiaomai

Powdery mildew, caused by fungal pathogen Blumeria graminis f. sp. tritici (Bgt), is one of agronomically important and widespread wheat diseases causing severe yield losses. Deployment of broad‐spectrum disease-resistance genes is the preferred strategy to prevent this pathogen. Chinese wheat landrace Honghuaxiaomai (HHXM) was resistant to all 23 tested Bgt isolates at the seedling stage. The F1, F2, and F2:3 progenies derived from the cross HHXM × Yangmai 158 were used in this study, and genetic analysis revealed that a single dominant gene, designated as PmHHXM, conferred resistance to Bgt isolate E09. Bulked segregant analysis and molecular mapping initially located PmHHXM to the distal region of chromosome 4AL. To fine map PmHHXM, two critical recombinants were identified from 592 F2 plants and delimited PmHHXM to a 0.18-cM Xkasp475200–Xhnu552 interval covering 1.77-Mb, in which a number of disease resistance-related gene clusters were annotated. Comparative mapping of this interval revealed a perturbed synteny among Triticeae species. This study reports the new powdery mildew resistance gene PmHHXM that seems different from three known QTL/genes identified on chromosome 4AL and has significant values for further genetic improvement. Analysis of the polymorphisms of 13 co-segregating markers between HHXM and 170 modern wheat cultivars indicates that Xhnu227 and Xsts478700 developed here are ideal for marker-assisted introgression of this resistance gene in wheat breeding.