Characterization of wheat-Thinopyrum bessarabicum genetic stock for stripe rust and Karnal bunt resistance

Utilization of modern breeding techniques for developing high yielding and uniform plant types ultimately narrowing the genetic makeup of most crops. Narrowed genetic makeup of these crops has made them vulnerable towards disease and insect epidemics. For sustainable crop production, genetic variability of these crops must be broadened against various biotic and abiotic stresses. One of the ways to widen genetic configuration of these crops is to identify novel additional sources of durable resistance. In this regard crops wild relatives are providing valuable sources of allelic diversity towards various biotic, abiotic stress tolerance and quality components. For incorporating novel variability from wild relative’s wide hybridization technique has become a promising breeding method. For this purpose, wheat-Th. bessarabicum amphiploid, addition and translocation lines have been screened in field and screen house conditions to get novel sources of yellow rust and Karnal bunt resistant. Stripe rust screening under field conditions has revealed addition lines 4JJ and 6JJ as resistant to moderately resistant while addition lines 3JJ, 5JJ, 7JJ and translocation lines Tr-3, Tr-6 as moderately resistant wheat-Thinopyrum-bessarabicum genetic stock. Karnal bunt screening depicted addition lines 5JJ and 4JJ as highly resistant genetic stock. These genetic stocks may be used to introgression novel stripe rust and Karnal bunt resistance from the tertiary gene pool into susceptible wheat backgrounds.

Development and characterization of novel wheat-rye 1RS•1BL translocation lines with high resistance to Puccinia striiformis f. sp. tritici

Wheat-rye 1RS•1BL translocations from Petkus rye have contributed substantially to wheat production worldwide with their great disease resistance and yield traits. However, the resistance genes on the 1RS chromosomes have completely lost their resistance to newly emerged pathogens. Rye could widen the variation of 1RS as a naturally cross-pollinated related species of wheat. In this study, we developed three new 1RS•1BL translocation lines by crossing rye inbred line BL1, selected from Chinese landrace rye Baili, with wheat cultivar Mianyang11. These three new translocation lines exhibited high resistance to the most virulent and frequently occurring stripe rust pathotypes and showed high resistance in the field where stripe rust outbreaks have been most severe in China. One new gene for stripe rust resistance, located on 1RS of the new translocation lines, is tentatively named YrRt1054. YrRt1054 confers resistance to Puccinia striiformis f. sp. tritici pathotypes that are virulent toward Yr9 and YrCn17. This new resistance gene, YrRt1054, is available for wheat improvement programs. The present study indicated that rye cultivars may carry additional untapped variation as potential sources of resistance.

Chromosome morphology and cytomolecular characteristics of the perennial rye cultivar ‘Kriszta’

The perennial Secale cereanum cultivar ‘Kriszta’ is an artificial hybrid of S. cereale and S. strictum ssp. anatolicum. From the cross between the wheat line Mv9kr1 and ‘Kriszta’, which aimed the transfer of beneficial traits from rye to wheat, numerous translocation lines have been produced. For the identification of the translocated chromosomes, the unambiguous differentiation between chromosome arms of ‘Kriszta’ is essential. The identification of its short chromosome arms using conventional FISH probes is easy, but because of their similar hybridization patterns, its long arms cannot be distinguished. The present study aimed to create the detailed karyotype of ‘Kriszta’, especially that of long arms, by both chromosome measurements and FISH using highly repetitive, as well as subtelomeric tandem repeat, and synthetic microsatellite DNA sequences. Our results indicate that the chromosome complement of ‘Kriszta’ is not a simple combination of the chromosomes of the parental rye species but is composed of rearranged chromosomes. It is also showed that an adequate pair-wise combination of the DNA sequences pSc119.2, pSc200, pSc250, and (AAC)5 makes it possible to identify any of the long arms of S. cereanum cv. Kriszta chromosomes. The future usability of the identified wheat- ‘Kriszta’ translocated chromosomes is also discussed.

Development of Novel Wheat-Aegilops longissima 3Sl Translocations Conferring Powdery Mildew Resistance and Specific Molecular Markers for Chromosome 3Sl

Powdery mildew of wheat, caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease of wheat. Cultivation of resistant varieties is the most cost-effective disease management strategy. Previous studies reported that chromosome 3Sl#2 present in Chinese Spring (CS)-Aegilops longissima 3Sl#2(3B) disomic substitution line TA3575 conferred resistance to powdery mildew. In this study, we further located the powdery mildew resistance gene(s) to the short arm of chromosome 3Sl#2 (3Sl#2S) by evaluating for Bgt-resistance of newly developed CS-Ae. longissima 3Sl#2 translocation lines. Meanwhile, TA7545, a previously designated CS-Ae. longissima 3Sl#3 disomic addition line, was re-identified as an isochromosome 3Sl#3S addition line and evaluated to confer resistance to powdery mildew, thus locating the resistance gene(s) to the short arm of chromosome 3Sl#3 (3Sl#3S). Based on transcriptome sequences of TA3575, ten novel chromosome 3SlS-specific markers were developed, of which, five could be used to distinguish between 3Sl#2S and 3Sl#3S derived from Ae. longissima accessions TL20 and TA1910 (TAM4), and the remaining five could identify both 3Sl#2S and 3Sl#3S. Besides, CL897, one of five markers specific to both 3Sl#2S and 3Sl#3S, could be used to detect Pm13 located at chromosome 3Sl#1S from Ae. longissima accession TL01 in diverse wheat genetic backgrounds. The powdery mildew resistance genes on chromosomes 3Sl#2S and 3Sl#3S, the CS-Ae. longissima 3Sl#2 translocation lines, and the 3SlS-specific markers developed in this study will provide new germplasm resources for powdery mildew resistance breeding and facilitate the transfer of Bgt-resistance genes into common wheat.

Genotypic and Phenotypic Characterization of Two Triticum aestivum L.—Dasypyrum villosum Translocations Lines in the Same Wheat Genetic Background

A wheat 660K chip was used to genotype two wheat-Dasypyrum villosum 6V#4S.6DL and 6V#2S.6AL translocation lines (A303 and B303) and their common wheat recurrent parent Wan7107. The results showed that these three lines have similar characteristics of base composition except for the translocation chromosomes. The alien translocation chromosomes have fewer homozygous and more heterozygous genotypes with more invalid probes. Distributions of SNPs between the translocation lines and Wan7107 were mainly dense on the regions of 6AS or 6DS as expected, but unexpectedly also on near the telomere of 2BS, and some regions of other wheat chromosomes. Meanwhile, the translocation lines A303 and B303 have 99.44% and 98.81% identical genotypes to Wan7107, respectively. Under the same genetic background, A303 and B303 showed different reactions to Blumeria graminis f. sp. tritici (Bgt) strains of powdery mildew. Both translocation lines have higher grain weight and plant height, and B303 has fewer spikelets compared to Wan7107. These results provide us a new insight into the genomic variation between the backcross generation plant and the recurrent parent, which is valuable information for understanding the relationship between wheat and the 6VS chromosome of D. villosum as well as the application potential of the alien chromosome arms.

Alien chromatin but not Fhb7 confers Fusarium head blight resistance in wheat breeding

Fusarium head blight (FHB), caused by Fusarium species, seriously threaten global wheat production. Three wheat-Th.elongatum FHB resistant translocation lines have been developed and used for breeding. Transcriptomic analysis identified a derivative glutathione S-transferase transcript T26102, which was homologous to Fhb7 and induced dramatically by Fusarium graminearum. Homologs of Fhb7 were detected in several genera in Triticeae, including Thinopyrum, Elymus, Leymus, Pseudoroegeria and Roegeria. Several wheat-Thinopyrum translocation lines carrying Fhb7 remain susceptible to FHB, and transgenic plants overexpressing the T26102 on different backgrounds did not improve the FHB resistance. Taken as a whole, we show the application of the chromatin derived from diploid Thinopyrum elongatum successfully conferring wheat with high level FHB resistance independent of the Fhb7.One Sentence SummaryThinopyrum elongatum chromatin from 7EL was successfully applied to wheat FHB resistance breeding, but the resistant gene other than the reported Fhb7 remained unknown.

Development and Characterization of Wheat-Agropyron cristatum Introgression Lines Induced by Gametocidal Genes and Wheat ph1b Mutant

The P genome of Agropyron cristatum Gaertn. contains many desirable genes that can be utilized as genetic resources to improve wheat. In this research, we used both the gametocidal chromosome 2Cc and the pairing homologous gene (Ph1b) mutant to induce structural aberrations and translocations between wheat and the 4P, 5P, and 6P genome chromosomes. By using the two approaches, a total of 19 wheat-A. cristatum translocations have been identified, in which 13 were induced by the Triticum aestivum cv. Chinese Spring (CS) ph1b mutant (CS ph1b) and six were induced by gametocidal chromosome 2Cc from Aegilops cylindrica Host. The wheat-4P, -5P and -6P A. cristatum translocations were characterized by in situ hybridization and by a set of conserved orthologous set (COS) molecular markers. The aberrations included centromeric translocations, terminal translocations, dicentric translocations, and deletions. The average induction frequency of chromosome structural aberrations was 10.9% using gametocidal 2Cc chromosome and 8.8% using ph1b mutant. The highest frequency obtained was for chromosome 4P using both approaches. All the wheat-A. cristatum translocation lines obtained were valuable for identifying A. cristatum chromosome 4P, 5P, and 6P related genes. In addition, these lines provided genetic resources and new germplasm accessions for the genetic improvement of wheat.