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.

Screening Chickpea Genotypes for Resistance to Rhizoctonia bataticola in Controlled Conditions

Among the various biotic stresses, dry root rot caused by Rhizoctonia bataticola is becoming severe in most chickpea growing regions of India where the crop is grown under rain fed conditions causing 30-40 per cent yield loss. In this context, 520 chickpea genotypes were screened in the laboratory condition using Blotter Paper Technique to study the reaction of the genotypes to the Rhizoctonia bataticola and to identify resistance source for the disease. Among 520 genotypes, three were resistant viz., PG 06102, BG 2094 and IC 552137; 21 were moderate resistant viz., IC 15167, IC 2867, JAKI 9218, ICC 9023, ICC-14346, IC-269768, PG 01103, Pule 9801, KGD 120, NbeG 28, WR 315, IC-269488, IC 552198, IC 552178, IC 552132, IC 552320, IC 552214, IC 552232, CLH 29, IC 552102, IC 552224; 76 were moderate susceptible, 337 were susceptible and the rest eighty three were highly susceptible for dry root rot. The identified resistant genotypes may serve as potential donors in chickpea resistance breeding programme for dry root rot.

Identification and Mapping of Eastern Filbert Blight Resistance Quantitative Trait Loci in European Hazelnut Using Double Digestion Restriction Site Associated DNA Sequencing

European hazelnut (Corylus avellana L.) is an economically important edible nut producing species, which ranked sixth in world tree nut production in 2016. European hazelnut production in the United States is primarily limited to the Willamette Valley of Oregon, and currently nonexistent in the eastern United States because of the presence of a devastating endemic disease, eastern filbert blight (EFB) caused by Anisogramma anomala (Peck) E. Muller. The primary commercial means of control of EFB to date is through the development and planting of genetically resistant european hazelnut cultivars, with an R-gene introduced from the obsolete, late-shedding pollinizer ‘Gasaway’. Although the ‘Gasaway’ resistance source provides protection against EFB in the Pacific northwestern United States (PNW), recent reports have shown that it is not effective in parts of the eastern United States. This may be in part because the identification and selection of ‘Gasaway’ and ‘Gasaway’-derived cultivars occurred in an environment (PNW) with limited genetic diversity of A. anomala. The objectives of the current research were to develop a genetic linkage map using double digestion restriction site associated DNA sequencing (ddRADseq) and identify quantitative trait loci (QTL) markers associated with EFB resistance from the resistant selection Rutgers H3R07P25 from southern Russia. A mapping population composed of 119 seedling trees was evaluated in a geographic location (New Jersey) where the EFB fungus is endemic, exhibits high disease pressure, and has a high level of genetic diversity. The completed genetic linkage map included a total of 2217 markers and spanned a total genetic distance of 1383.4 cM, with an average marker spacing of 0.65 cM. A single QTL region associated with EFB resistance from H3R07P25 was located on european hazelnut linkage group (LG) 2 and was responsible for 72.8% of the phenotypic variation observed in the study. Based on its LG placement, origin, and disease response in the field, this resistance source is different from the ‘Gasaway’ source located on LG6. The current results, in combination with results from previous research, indicate that the H3R07P25 source is likely exhibiting resistance to a broader range of naturally occurring A. anomala isolates. As such, H3R07P25 will be important for the development of new european hazelnut germplasm that combines EFB resistance from multiple sources in a gene pyramiding approach. Identification of EFB resistance in high disease pressure environments representing a diversity of A. anomala populations is likely a requirement for identifying plants expressing durable EFB resistance, which is a precursor to the development of a commercially viable european hazelnut industry in the eastern United States.

Genome Sequence of Ralstonia pseudosolanacearum Strains with Compatible and Incompatible Interactions with the Major Tomato Resistance Source Hawaii 7996

ABSTRACT We report here the complete genome sequences of two Ralstonia pseudosolanacearum strains, isolated from the warm northeast region of Brazil. They display divergent (compatible versus incompatible) interactions with the resistant tomato line Hawaii 7996. Polymorphisms were detected in a subset of effector genes that might be associated with these contrasting phenotypes.