The Australian Ascochyta rabiei (Pass.) Labr. (syn. Phoma rabiei) population has low genotypic diversity with only one mating type detected to date, potentially precluding substantial evolution through recombination. However, a large diversity in aggressiveness exists. In an effort to better understand the risk from selective adaptation to currently used resistance sources and chemical control strategies, the population was examined in detail. For this, a total of 598 isolates were quasi-hierarchically sampled between 2013 and 2015 across all major Australian chickpea growing regions and commonly grown host genotypes. Although a large number of haplotypes were identified (66) through short sequence repeat (SSR) genotyping, overall low gene diversity (H-exp = 0.066) and genotypic diversity (D = 0.57) was detected. Almost 70% of the isolates assessed were of a single dominant haplotype (ARH01). Disease screening on a differential host set, including three commonly deployed resistance sources, revealed distinct aggressiveness among the isolates, with 17% of all isolates identified as highly aggressive. Almost 75% of these were of the ARH01 haplotype. A similar pattern was observed at the host level, with 46% of all isolates collected from the commonly grown host genotype Genesis090 (classified as "resistant" during the term of collection) identified as highly aggressive. Of these, 63% belonged to the ARH01 haplotype. In conclusion, the ARH01 haplotype represents a significant risk to the Australian chickpea industry, being not only widely adapted to the diverse agro-geographical environments of the Australian chickpea growing regions, but also containing a disproportionately large number of aggressive isolates, indicating fitness to survive and replicate on the best resistance sources in the Australian germplasm.

Key message Significant differences in defence pathway-related gene expression were observed among chickpea cultivars following A. rabiei infection. Differential gene expression is indicative of diverse resistances, a theoretical tool for selective breeding. Abstract A high number of Ascochyta rabiei pathotypes infecting chickpea in Australia has severely hampered efforts towards breeding for sustained quantitative resistance in chickpea. Breeding for sustained resistance will be aided by detailed knowledge of defence responses to isolates with different aggressiveness. As an initial step, the conserved and differential expressions of a suit of previously characterised genes known to be involved in fungal defence mechanisms were assessed among resistant and susceptible host genotypes following inoculation with high or low aggressive A. rabiei isolates. Using quantitative Real-Time PCR (qRT-PCR), 15 defence-related genes, normalised with two reference genes, were temporally differentially expressed ( P < 0.005) as early as 2 h post inoculation of Genesis090 (resistant) or Kaniva (susceptible). The highly aggressive isolate, 09KAL09, induced vastly different expression profiles of eight key defence-related genes among resistant and susceptible genotypes. Six of these same genes were differentially expressed among ten host genotypes, inclusive of the best resistance sources within the Australian chickpea breeding program, indicating potential use for discrimination and selection of resistance “type” in future breeding pursuits.

The study examined the genetic structure and potential for adaption to host genotype of Ascochyta rabiei, a major necrotrophic fungal pathogen of chickpea. For this, A. rabiei populations derived from six major chickpea growing regions in Australia were characterized using 20 polymorphic microsatellite markers. The overall gene (H = 0.094) and genotypic (D = 0.80) diversities among the entire population were low, indicating the establishment of a recent founder population. Since, no significant genetic differentiation was detected among growing regions, subsequent anthropogenic dispersal was proposed, mainly through seed movement. The highest genotypic diversity and allelic richness was detected at Kingsford, South Australia, thought to be one of the sites of industry establishment in the 1970s and hence the centre of introduction. Despite assessing 206 isolates collected in 2010 from host genotypes with differential disease responses, no significant co-occurrence of fungal haplotype with host genotype was detected. Rather a single haplotype that accounted for 70 % of the total isolates assessed was detected on all host genotypes assessed and from all regions. Therefore, we propose that up until 2010, host reaction was not a major influence on the Australian A. rabiei population structure. Additionally, the detection of a single mating type only, MAT1-2 indicated asexual reproduction, further influencing low haplotype diversity and resulting in a population comprising of multiple clones with relatively few haplotypes compared to populations in other continents.

Projected climatic impacts on crop yield and quality, and increased demands for production, require targeted research to optimise nutrition of crop plants. For wheat, post-anthesis carbon and nitrogen remobilisation from vegetative plant parts and translocation to grains directly affects grain carbon (C), nitrogen (N) and protein levels. We analysed the influence of increased atmospheric CO2 on the expression of genes involved in senescence, leaf carbohydrate and nitrogen metabolism and assimilate transport in wheat under field conditions (Australian Grains Free Air CO2 Enrichment; AGFACE) over a time course from anthesis to maturity, the key period for grain filling. Wheat grown under CO2 enrichment had lower N concentrations and a tendency towards greater C/N ratios. A general acceleration of the senescence process by elevated CO2 was not confirmed. The expression patterns of genes involved in carbohydrate metabolism, nitrate reduction and metabolite transport differed between CO2 treatments, and this CO2 effect was different between pre-senescence and during senescence. The results suggest up-regulation of N remobilisation and down-regulation of C remobilisation during senescence under elevated CO2, which is consistent with greater grain N-sink strength of developing grains.

This study focused on the implementation of microsatellite markers to determine the diversity among elite inbred lines representing the Vietnamese maize breeding program.Genetic relationships were assessed using twenty loci to gain an understanding of the width of the program compared to other Asia programs, as well as develop a DNA fingerprint database.The PIC value of the 20 loci ranged from 0.10 to 0.83 with those containing a tetra-repeat the most informative (mean PIC = 0.60).The amount of genetic diversity among the lines assessed was similar to the levels identified in other Asian breeding programs.Future monitoring will be important to maintain genetic breadth of the Vietnamese program and minimize risks from narrowing in future targeted selective breeding strategies.This will be facilitated through implementation of the developed robust SSR-based DNA fingerprint database, which will also be used for true-to-type identification, hybrid confirmation and potential trait selection.

This article documents the addition of 277 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Ascochyta rabiei, Cambarellus chapalanus, Chionodraco hamatus, Coptis omeiensis, Cynoscion nebulosus, Daphnia magna, Gerbillus nigeriae, Isurus oxyrinchus, Lates calcarifer, Metacarcinus magister, Oplegnathus fasciatus, Pachycondyla verenae, Phaethon lepturus, Pimelodus grosskopfii, Rotylenchulus reniformis, Scomberomorus niphonius, Sepia esculenta, Terapon jarbua, Teratosphaeria cryptica and Thunnus obesus . These loci were cross‐tested on the following species: Austropotamobius italicus, Cambarellus montezumae, Cambarellus puer, Cambarellus shufeldtii, Cambarellus texanus, Chionodraco myersi, Chionodraco rastrospinosus, Coptis chinensis, Coptis chinensis var. brevisepala, Coptis deltoidea, Coptis teeta, Orconectes virilis, Pacifastacus leniusculus, Pimelodus bochii, Procambarus clarkii, Pseudopimelodus bufonius, Rhamdia quelen, Sepia andreana, Sepiella maindroni, Thunnus alalunga, Thunnus albacares, Thunnus maccoyii, Thunnus orientalis, Thunnus thynnus and Thunnus tonggol.