A review of viruses infecting yam (Dioscorea spp.)

Yam is an important food staple for millions of people globally, particularly those in the developing countries of West Africa and the Pacific Islands. To sustain the growing population, yam production must be increased amidst the many biotic and abiotic stresses. Plant viruses are among the most detrimental of plant pathogens and have caused great losses of crop yield and quality, including those of yam. Knowledge and understanding of virus biology and ecology are important for the development of diagnostic tools and disease management strategies to combat the spread of yam-infecting viruses. This review aims to highlight current knowledge on key yam-infecting viruses by examining their characteristics, genetic diversity, disease symptoms, diagnostics, and elimination to provide a synopsis for consideration in developing diagnostic strategy and disease management for yam.The ‘Pacific Seeds for Life’ project funded by the Ministry of Foreign Affairs and Trade (MFAT) of New Zealand through the Manaaki Whenua—Landcare Research. G.L. is funded under the ‘Transforming the Centre for Pacific Crops and Trees (CePaCT) into a Centre of Excellence’ project funded by the Australian Department of Foreign Affairs and Trade (DFAT), Australia.https://www.mdpi.com/journal/virusesam2023Forestry and Agricultural Biotechnology Institute (FABI)Plant Production and Soil Scienc

Environmental and biotic influences on the maintenance of apomixis

Most plant species that reproduce by the production of clonal seed (apomicts) retain some capacity for sexual reproduction (facultative apomixis). The frequency of this residual sexual reproduction in apomicts varies, even within a species, and this variation has often been attributed to the environment. This study aims to investigate the role of the environment on the expression of apomixis in the facultative apomict, Hieracium pilosella. H. pilosella has been chosen for this study because it is a widespread, exotic, species that possesses a facultative reproductive system. Additionally, there is interest in its' reproductive pathway as a potential source of genetic material for apomictic cropping technology. Field experiments examining the reproductive mode of Hieracium pilosella found there was a positive relationship between the frequency of sexual reproduction, and both temperature and rainfall for the seven days prior to pollination (at capitulum anthesis). The frequency of sex in all experiments was determined by pollinating H pilosella with a marker pollen donor, either the morphologically distinct H aurantiacum, or transgenic accessions of Hieracium spp. with a kanamycin resistance insert, and using hybrid characteristics as a measure. Both field and glasshouse studies demonstrated a genetic component to the frequency of sex; while neither photoperiod, nutrient level, or the presence of a powdery mildew (Erysiphe spp.) had a significant effect on residual sexuality. Additionally, it was demonstrated that sexual events, although contributing only 0.2 6.0 % of total seed progeny in apomictic populations, are important in determining population genetic diversity. The existence a flexible reproductive strategy indicates that both reproductive pathways are beneficial, or at least the cost of reproducing sexually (as predicted by evolutionary models) is insufficient to lead to its' loss. The maintenance of this rate of sexual reproduction, and the potential for it to generate population variation, may increase the complexity of both the transfer of genetic material from Hieracium pilosella to crop species, and biological control

Nonneutral Evolution of Organelle Genes in Silene vulgaris

Knowledge of mitochondrial gene evolution in angiosperms has taken a dramatic shift within the past decade, from universal slow rates of nucleotide change to a growing realization of high variation in rates among lineages. Additionally, evidence of paternal inheritance of plant mitochondria and recombination among mitochondrial genomes within heteroplasmic individuals has led to speculation about the potential for independent evolution of organellar genes. We report intraspecific mitochondrial and chloroplast sequence variation in a cosmopolitan sample of 42 Silene vulgaris individuals. There was remarkably high variation in two mitochondrial genes (atp1, atp9) and additional variation within a third gene (cob). Tests for patterns of nonneutral evolution were significant for atp1 and atp9, indicative of the maintenance of balanced polymorphisms. Two chloroplast genes (matK, ndhF) possessed less, but still high, variation and no divergence from neutral expectations. Phylogenetic patterns of organelle genes in both the chloroplast and mitochondria were incongruent, indicating the potential for independent evolutionary trajectories. Evidence indicated reassociation among cytoplasmic genomes and recombination between mitochondrial genes and within atp1, implying transient heteroplasmy in ancestral lineages. Although the mechanisms for long-term maintenance of mitochondrial polymorphism are currently unknown, frequency-dependent selection on linked cytoplasmic male sterility genes is a potential candidate

Genetic Variation and Hybridisation among Eight Species of kōwhai (Sophora: Fabaceae) from New Zealand Revealed by Microsatellite Markers

We analysed nine microsatellite markers for 626 individuals representing the geographic range of eight closely related endemic New Zealand species of Sophora. Structure analysis identified the optimal K value as seven, with samples identified as Sophora chathamica, Sophora fulvida, Sophora longicarinata, and Sophora prostrata retrieved as well-defined groups. The remaining samples formed less resolved groups referable to Sophora tetraptera and Sophora godleyi, with Sophora microphylla and Sophora molloyi forming the seventh group. Our data suggest that considerable admixture occurs and this is most likely the result of hybridisation or introgression. S. fulvida shows admixture with the sympatric S. chathamica, and the widespread S. microphylla exhibits admixture with the sympatric S. godleyi, S. molloyi, and S. tetraptera

Cost-Effective Microsatellite Markers for <i>Banksia integrifolia</i> (Proteaceae)

Premise of the study: Microsatellite markers were developed to assess the level of genetic variation and population structure in <i>Banksia integrifolia</i>, a widespread species endemic to eastern Australia. Methods and Results: We used next-generation sequencing approaches to identify and develop 11 polymorphic microsatellite markers with perfect tri- and tetranucleotide repeats. We tested these markers with 71 specimens from three populations. Observed and expected heterozygosities ranged from 0.0 to 0.875 and 0.0 to 0.763, respectively. Conclusions: The developed markers will be valuable for studies of the population structure, mating system, and selection of provenances for restoration projects involving <i>B. integrifolia</i>

New Lepidium (Brassicaceae) from New Zealand

A revision of the New Zealand endemic Lepidium oleraceum and allied species is presented. Sixteen species are recognised, 10 of these are new. The new species are segregated on the basis of morphological characters supported by molecular data obtained from three DNA markers (two rDNA and one cpDNA). One species, L. castellanum sp. nov., is endemic to the Kermadec Islands where it is sympatric with L. oleraceum. The North Island of New Zealand supports four species, with two of them, L. amissum sp. nov. and L. obtusatum, now extinct. The South Island supports six species, that, aside from L. banksii, L. flexicaule and L. oleraceum, are all confined to the south-eastern half of the island (L. aegrum sp. nov., L. crassum sp. nov. and L. juvencum sp. nov.). One of these, L. juvencum sp. nov., extends to Stewart Island. The Chatham Islands support six species (L. flexicaule, L. oblitum sp. nov., L. oleraceum, L. oligodontum sp. nov., L. panniforme sp. nov., and L. rekohuense sp. nov.), one of which, L. oligodontum sp. nov., extends to the Antipodes Islands group. The remote, subantarctic Bounty Islands group supports one endemic, L. seditiosum sp. nov., which is the only vascular plant to be recorded from there. Lepidium limenophylax sp. nov. is known from islands off the south-western side of Stewart Island/Rakiura, The Snares and Auckland islands. Lepidium naufragorum, although not related to L. oleraceum and its allies, is also treated because populations with entire leaves are now known. Typification is undertaken for L. banksii, L. oleraceum, L. oleraceum var. acutidentatum, var. frondosum and var. serrulatum

A Review of Viruses Infecting Yam (Dioscorea spp.)

Yam is an important food staple for millions of people globally, particularly those in the developing countries of West Africa and the Pacific Islands. To sustain the growing population, yam production must be increased amidst the many biotic and abiotic stresses. Plant viruses are among the most detrimental of plant pathogens and have caused great losses of crop yield and quality, including those of yam. Knowledge and understanding of virus biology and ecology are important for the development of diagnostic tools and disease management strategies to combat the spread of yam-infecting viruses. This review aims to highlight current knowledge on key yam-infecting viruses by examining their characteristics, genetic diversity, disease symptoms, diagnostics, and elimination to provide a synopsis for consideration in developing diagnostic strategy and disease management for yam

A Review of Viruses Infecting Yam (<i>Dioscorea</i> spp.)

Yam is an important food staple for millions of people globally, particularly those in the developing countries of West Africa and the Pacific Islands. To sustain the growing population, yam production must be increased amidst the many biotic and abiotic stresses. Plant viruses are among the most detrimental of plant pathogens and have caused great losses of crop yield and quality, including those of yam. Knowledge and understanding of virus biology and ecology are important for the development of diagnostic tools and disease management strategies to combat the spread of yam-infecting viruses. This review aims to highlight current knowledge on key yam-infecting viruses by examining their characteristics, genetic diversity, disease symptoms, diagnostics, and elimination to provide a synopsis for consideration in developing diagnostic strategy and disease management for yam