A Review on Nucleotide Binding Site – Leucine Rich Repeats Disease Resistance Genes in legumes

The crop plants of the family Leguminosae are second to cereal crops of commercial importance on the basis of area harvested and total production worldwide. It is well known globally that many crops do not give good yield due to certain diseases existing in their plants. Nowadays, there is much emphasis on developing disease resistant varieties of crops and especially of commercial crops. Plants need to protect themselves against attack from viruses, microbes, invertebrates and even other plants. NBS-LRR (Nucleotide binding site-leucine rich repeats) genes belong to the largest plant disease resistance gene family and are responsible for plant resistance to pathogens. Studies of the NBS-LRR gene family in plants represent an intriguing challenge and can provide knowledge on the genomic and molecular mechanisms that form the basis of gene regulation and protein function. Their evolution at the gene and genomic level can be defined through ancient and numerous gene families. In the present study, beneficial concepts for generating basic and fundamental knowledge on the NBS-LRR plant disease resistance genes are discussed with emphasis on selected legume plants of commercial importance.

Aegilops tauschii genome assembly Aet v5.0 features greater sequence contiguity and improved annotation

Aegilops tauschii is the donor of the D subgenome of hexaploid wheat and an important genetic resource. The reference-quality genome sequence Aet v4.0 for Ae. tauschii acc. AL8/78 was therefore an important milestone for wheat biology and breeding. Further advances in sequencing acc. AL8/78 and release of the Aet v5.0 sequence assembly are reported here. Two new optical maps were constructed and used in the revision of pseudomolecules. Gaps were closed with Pacific Biosciences long-read contigs, decreasing the gap number by 38,899. Transposable elements and protein-coding genes were reannotated. The number of annotated high-confidence genes was reduced from 39,635 in Aet v4.0 to 32,885 in Aet v5.0. A total of 2,245 biologically important genes, including those affecting plant phenology, grain quality, and tolerance of abiotic stresses in wheat was manually annotated and disease-resistance genes were annotated by a dedicated pipeline. Disease-resistance genes encoding nucleotide-binding site domains, receptor-like protein kinases, and receptor-like proteins were preferentially located in distal chromosome regions, whereas those encoding transmembrane coiled-coil proteins were dispersed more evenly along the chromosomes. Discovery, annotation, and expression analyses of microRNA (miRNA) precursors, mature miRNAs, and phasiRNAs are reported, including miRNA target genes. Other small RNAs, such as hc-siRNAs and tRFs, were characterized. These advances enhance the utility of the Ae. tauschii genome sequence for wheat genetics, biotechnology, and breeding.

Comparative Transcriptome Analysis Identified Candidate Genes for Late Leaf Spot Resistance and Cause of Defoliation in Groundnut

Late leaf spot (LLS) caused by fungus Nothopassalora personata in groundnut is responsible for up to 50% yield loss. To dissect the complex nature of LLS resistance, comparative transcriptome analysis was performed using resistant (GPBD 4), susceptible (TAG 24) and a resistant introgression line (ICGV 13208) and identified a total of 12,164 and 9954 DEGs (differentially expressed genes) respectively in A- and B-subgenomes of tetraploid groundnut. There were 135 and 136 unique pathways triggered in A- and B-subgenomes, respectively, upon N. personata infection. Highly upregulated putative disease resistance genes, an RPP-13 like (Aradu.P20JR) and a NBS-LRR (Aradu.Z87JB) were identified on chromosome A02 and A03, respectively, for LLS resistance. Mildew resistance Locus (MLOs)-like proteins, heavy metal transport proteins, and ubiquitin protein ligase showed trend of upregulation in susceptible genotypes, while tetratricopeptide repeats (TPR), pentatricopeptide repeat (PPR), chitinases, glutathione S-transferases, purple acid phosphatases showed upregulation in resistant genotypes. However, the highly expressed ethylene responsive factor (ERF) and ethylene responsive nuclear protein (ERF2), and early responsive dehydration gene (ERD) might be related to the possible causes of defoliation in susceptible genotypes. The identified disease resistance genes can be deployed in genomics-assisted breeding for development of LLS resistant cultivars to reduce the yield loss in groundnut.

Genome Enhanced Marker Improvement for Potato Virus Y Disease Resistance in Potato

Potato is an important food crop worldwide and is grown in a large number of countries. As such, the crop is under disease pressures and the need for selecting disease resistance genes during breeding programs is essential. Of particular importance within Australia and other parts of the world is the potyvirus, Potato virus Y (PVY). In this paper, three commonly used PVY resistance markers, M45, RYSC3 and M6, were evaluated using existing genomic resources and phenotypic data from the Australian potato breeding program to identify a region where the PVY resistance gene, Ryadg may reside. A region of Chromosome XI was investigated, and a cluster of disease resistance genes was identified that the resistance gene Ryadg is suspected to reside within. Protein characterization was also performed on the putative resistant gene. A specific variant that had complete association with the resistance gene was identified and a single nucleotide polymorphism (SNP) assay was designed to avoid dissociation of marker and gene in future breeding programs. This SNP marker (SNP37279) was validated as a Kompetitive Allele-specific PCR (KASP) genotyping assay and was found to perform more accurately than all previously used markers for detecting Ryadg.