Epidemiology of Zucchini yellow mosaic virus in cucurbit crops in a remote tropical environment

Efficient CRISPR/Cas9-mediated genome editing in Rehmannia glutinosa

Here, we cloned a phytoene desaturase (PDS) gene from Rehmannia glutinosa, and realized RgPDS1 knock out in R. glutinosa resulted in the generation of albino plants. Rehmannia glutinosa is a highly important traditional Chinese medicine (TCM) with specific pharmacology and economic value. R. glutinosa is a tetraploid plant, to date, no report has been published on gene editing of R. glutinosa. In this study, we combined the transcriptome database of R. glutinosa and the reported phytoene desaturase (PDS) gene sequences to obtain the PDS gene of R. glutinosa. Then, the PDS gene was used as a marker gene to verify the applicability and gene editing efficiency of the CRISPR/Cas9 system in R. glutinosa. The constructed CRISPR/Cas9 system was mediated by Agrobacterium to genetically transform into R. glutinosa, and successfully regenerated fully albino and chimeric albino plants. The next-generation sequencing (NGS) confirmed that the albino phenotype was indeed caused by RgPDS gene target site editing, and it was found that base deletion was more common than insertion or replacement. Our results revealed that zCas9 has a high editing efficiency on the R. glutinosa genome. This research lays a foundation for further use of gene editing technology to study the molecular functions of genes, create excellent germplasm, accelerate domestication, and improve the yield and quality of R. glutinosa.

Global Plant Virus Disease Pandemics and Epidemics

The world's staple food crops, and other food crops that optimize human nutrition, suffer from global virus disease pandemics and epidemics that greatly diminish their yields and/or produce quality. This situation is becoming increasingly serious because of the human population's growing food requirements and increasing difficulties in managing virus diseases effectively arising from global warming. This review provides historical and recent information about virus disease pandemics and major epidemics that originated within different world regions, spread to other continents, and now have very wide distributions. Because they threaten food security, all are cause for considerable concern for humanity. The pandemic disease examples described are six (maize lethal necrosis, rice tungro, sweet potato virus, banana bunchy top, citrus tristeza, plum pox). The major epidemic disease examples described are seven (wheat yellow dwarf, wheat streak mosaic, potato tuber necrotic ringspot, faba bean necrotic yellows, pepino mosaic, tomato brown rugose fruit, and cucumber green mottle mosaic). Most examples involve long-distance virus dispersal, albeit inadvertent, by international trade in seed or planting material. With every example, the factors responsible for its development, geographical distribution and global importance are explained. Finally, an overall explanation is given of how to manage global virus disease pandemics and epidemics effectively.

Host plant affiliations of aphid vector species found in a remote tropical environment

The Ord River Irrigation Area (ORIA) produces annual crops during the dry season (April to October), and perennial crops all-year-round, and is located in tropical northwestern Australia. Sandalwood plantations cover 50 % of the ORIA's cropping area. Aphids cause major crop losses through transmission of viruses causing debilitating diseases and direct feeding damage. During 2016-2017, in both dry and wet seasons a total of 3320 leaf samples were collected from diverse types of sites on cultivated and uncultivated land and 1248 (38 %) of them were from aphid-colonized plants. In addition, aphids were found at 236 of 355 sampling sites. The 62 plant species sampled came from 23 families 19 of which contained aphid-colonized species. Aphid hosts included introduced weeds, Australian native plants, and volunteer or planted crop plants. Six aphid species were identified by light microscopy and CO1 gene sequencing, but there was no within species nucleotide sequence diversity. Aphis nerii, Hysteroneura setariae, Rhopalosiphum maidis and Schoutedenia ralumensis each colonized 1-3 plant species from a single plant family. A. craccivora colonized 14 species in five plant families. A. gossypii was the most polyphagous species colonizing 19 species in 11 plant families. A. gossypii, A. craccivora, A. nerii and S. ralumensis were found in both wet and dry seasons. Because of A. craccivora's prevalence and high incidences on understory weeds and host trees, sandalwood plantations were important reservoirs for aphid spread to wild and crop plant hosts growing in cultivated and uncultivated land. Alternative hosts growing in rural bushland, irrigation channel banks, vacant or fallow land, and orchard plantation understories also constituted significant aphid reservoirs. This study provides new knowledge of the ecology of aphid vector species not only in the ORIA but also in tropical northern Australia generally. It represents one of relatively few investigations on aphid ecology in tropical environments worldwide.