Domestic sheep and their wild relatives harbor substantial genetic variants that can form the backbone of molecular breeding, but their genome landscapes remain understudied. Here, we present a comprehensive genome resource for wild ovine species, landraces and improved breeds of domestic sheep, comprising high-coverage (∼16.10×) whole-genomes of 810 samples from 7 wild species and 158 diverse domestic populations. We detected, in total, ∼121.2 million single nucleotide polymorphisms (SNPs), ∼61 million of which are novel. Some display significant (P < 0.001) differences in frequency between wild and domestic species, or are private to continent-wide or individual sheep populations. Retained or introgressed wild gene variants in domestic populations have contributed to local adaptation, such as the variation in the HBB associated with plateau adaptation. We identified novel and previously reported targets of selection on morphological and agronomic traits such as stature, horn, tail configuration and wool fineness. We explored the genetic basis of wool fineness and unveiled a novel mutation (chr25: T7068586C) in the 3’-UTR of IRF2BP2 as plausible causal variant for fleece fiber diameter. We reconstructed pre-historical migrations from the Near Eastern domestication center to South-and-Southeast Asia, and found two main waves of migrations across the Eurasian Steppe and the Iranian Plateau in the Early and Late Bronze Ages. Our findings refine our understanding of genome variation as shaped by continental migrations, introgression, adaptation and selection of sheep.

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Cucumber green mottle mosaic virus (CGMMV) is transmitted mechanically in cucurbits, but whether it is transmitted via pollen to healthy plants and onto the subsequent generation of seedlings is unknown. Greenhouse experiments were conducted to investigate the importance of this route of infection. Cucumber seedlings at the 3-true-leaf stage were mechanically inoculated with CGMMV. At anthesis, scanning electron microscopy (SEM) and reverse transcription polymerase chain reaction (RT-PCR) were used to verify the presence of CGMMV. Pollen was collected from the flowers of the infected plants and used to fertilize non-inoculated plants. The rate of CGMMV transmission to the resulting fruits ranged from 17Á1 to 51Á2% compared with 33Á3-100% for mechanically inoculated plants. Seeds were harvested from the cucumber fruits of both treatments and tested for the presence of CGMMV by RT-PCR. The CGMMV-positive seeds harvested from the two treatments were sown separately. The seed transmission rates for the inoculated and non-inoculated plants were 16Á7-100% and 12Á8-76Á7%, respectively. It was concluded that CGMMV can be transmitted both horizontally via cucumber pollen and vertically, to the next generation, in infected seeds. In addition the rate of seed transmission was much higher than previous reports. These findings have important implications for the disease management of CGMMV.

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Bacterial canker of tomato is an economically important seedborne disease caused by Clavibacter michiganensis subsp. michiganensis (Cmm). Copper‐based bactericides and seed treatment with hydrochloric acid are commonly used for bacterial canker management. Recent studies have shown that some bacteria can enter a viable but nonculturable (VBNC) state, and fail to form colonies on microbiological agar media. Bacteria in the VBNC state can recover their culturability when returned to favourable conditions. This study reports the induction of the VBNC state in Cmm by CuSO4 and low pH, and resuscitation of VBNC cells on tomato seedlings. Flow cytometry using the nucleic acid dyes SYTO 9 and propidium iodide, combined with agar plating, was used to assess VBNC cell counts. It was demonstrated that CuSO4 and low pH induced the VBNC state in Cmm and the rate of induction increased with copper ion concentration and acidity. Pathogenicity tests showed that some of the VBNC cells induced by CuSO4 retained their ability to colonize tomato seedlings but failed to produce typical bacterial canker symptoms by 2 months post‐inoculation. This was probably due to low levels of resuscitation of VBNC Cmm cells resulting in low levels of initial inoculum. This study has improved understanding of the VBNC state of Gram‐positive phytopathogenic bacteria. Most importantly, because copper‐based chemicals and low pH conditions are used for disease management, induction of the VBNC state and subsequent resuscitation of Cmm cells on tomato seedlings may limit pathogen detection by culture‐based assays yet present a risk for disease development in the field.