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Phytoplasmas are phloem-limited plant pathogens, such as sugarcane white leaf (SCWL) phytoplasma, which are responsible for heavy economic losses to the sugarcane industry. Characterization of phytoplasmas has been limited because they cannot be cultured in vitro. However, with the advent of genome sequencing, different aspects of phytoplasmas are being investigated. In this study, we developed a DNA enrichment method for sugarcane white leaf (SCWL) phytoplasma, evaluated the effect of DNA enrichment via Illumina sequencing technologies, and utilized Illumina and Nanopore sequencing technologies to obtain the complete genome sequence of the “Candidatus Phytoplasma sacchari” isolate SCWL1 that is associated with sugarcane white leaf in China. Illumina sequencing analysis elucidated that only 1.21% of the sequencing reads from total leaf DNA were mapped to the SCWL1 genome, whereas 40.97% of the sequencing reads from the enriched DNA were mapped to the SCWL1 genome. The genome of isolate SCWL1 consists of a 538,951 bp and 2976 bp long circular chromosome and plasmid, respectively. We identified 459 protein-encoding genes, 2 complete 5S-23S-16S rRNA gene operons, 27 tRNA genes, and an incomplete potential mobile unit (PMU) in the circular chromosome. Phylogenetic analyses and average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values based on the sequenced genome revealed that SCWL phytoplasma and sugarcane grassy shoot (SCGS) phytoplasma belonged to the same phytoplasma species. This study provides a genomic DNA enrichment method for phytoplasma sequencing. Moreover, we report the first complete genome of a “Ca. Phytoplasma sacchari” isolate, thus contributing to future studies on the evolutionary relationships and pathogenic mechanisms of “Ca. Phytoplasma sacchari” isolates.

Phytoplasmas are important prokaryotic pathogenic bacteria without cell walls, which were formerly known as mycoplasma-like organisms, and belong to the Mollicutes class, Candidatus Phytoplasma genus. They are widely distributed in plants and insects, and can cause serious diseases in important food crops, vegetables, fruit trees, ornamental plants and trees, resulting in huge economic losses. To date, more than 100 phytoplasma diseases have been reported in China, which are distributed throughout the country. Jujube witches'-broom, paulownia witches'-broom, wheat blue dwarf, banana bunchy top, sugarcane white leaf, rice orange leaf and mulberry dwarf represent the phytoplasma diseases causing the most serious damage in China. New phytoplasma diseases and their strains are being reported continuously, indicating that phytoplasmas are more diverse than previously thought. Phytoplasmas are mainly transmitted by insect vectors, such as leafhopper and planthopper, and can also be spread by grafting or Cuscuta australis (known as dodder). Mixed infections of phytoplasmas and viruses, bacteria, and spiroplasmas have also become a serious problem in several crops and are responsible for more synergistic losses. With the continuous development and improvement of technology, molecular biological detection has become the main technique for phytoplasma detection and identification. Currently, research on phytoplasma diseases in China mainly focuses on pathogen identification and classification, and insect vector and host diversity; however, there is less focus on pathogenicity, comparative genomics, and effect factors. More research attention has been paid to wheat blue dwarf phytoplasma, paulownia witches'-broom phytoplasma, jujube witches'-broom phytoplasma, and sugarcane white leaf phytoplasma. Other phytoplasma diseases have been reported; however, there have been no in-depth studies. In this paper, the history and present situation of phytoplasma research, and the status, distribution, and diversity of phytoplasma diseases are summarized, and some possible research directions of phytoplasma in the future in China are proposed.

Quantification of resistance to borer pest damage in sugarcane varieties is key to sustainable crop protection and integrate pest management. Here, were assessed resistance to damage caused by two species of borer in seedlings of 12 new sugarcane varieties. The results showed that there were differences in resistance among the varieties, where varieties YT60, GT31, GT29, LC05-136, and YT55 were classified as showing moderate resistance, YZ06-407, YZ05-51, ROC22, YZ05-49, YZ03-194, and FN38 were found to be susceptible, and FN39 and DZ03-83 were shown to be highly susceptible. This study established a method to assess sugarcane seedling resistance to borer species that could be used in future resistance evaluations of novel sugarcane varieties during the crop breeding process. [ABSTRACT FROM AUTHOR]

The sugarcane borer is a type of pest that severely damages sugarcane. To explore and seek effective and environmentally friendly control technology for sugarcane borers, promote environmentally friendly control for sugarcane pests, new sex pheromone trap of sugarcane borers, Abamectin•Bacillus thuringiensis and Tebufenozide were selected and applied for control of Sesamia inferens Walker and Argyroploce schistaceana (Snellen). The results showed that new sex pheromone trap of sugarcane borers in combination with Abamectin•Bacillus thuringiensis or Tebufenozide were the optimum mode for environmentally friendly control techniques of Sesamia inferens Walker and Argyroploce schistaceana (Snellen). The use of new sex pheromone traps of sugarcane borers (6 a/ha) + 0.05% Abamectin•10 billion active gemma/g Bacillus thuringiensis WP (1800 g/ha) or new sex pheromone traps of sugarcane borers (6 a/ha) + 200g/L Tebufenozide SC (1500 mL/ha) were the best. The control effect of dead heart rate and bored stem rate could be more than 69.98% and 49.09%, respectively, and were superior to the control pesticide 3.6% Bisultap GR (90 kg/ha). [ABSTRACT FROM AUTHOR]

The aim of this study was to assess brown rust resistance in 60 new sugarcane varieties bred by the China Sugarcane System in recent years and in 34 major varieties cultivated in sugarcane growing areas in China. The resistance of these sugarcane varieties to brown rust was investigated in the field, and molecular markers were used to detect the brown rust-resistance gene Bru1. The results of the field survey showed that 66 (70.21%) of the 94 sugarcane varieties were highly resistant to moderately resistant, and 28 (29.79%) were susceptible to highly susceptible. The Bru1 gene was detected in 54 (57.45%) of the 94 sugarcane varieties. Seven highly resistant varieties and five resistant varieties did not carry Bru1, suggesting that they carry other genes associated with brown rust resistance. This study provides a scientific basis and identifies disease-resistant germplasm for selection of plants for sugarcane production. [ABSTRACT FROM AUTHOR]

This paper summarizes the natural enemies of major sugarcane pests and their roles in natural control in sugarcane growing regions in Yunnan. In general, these natural enemies can be divided into two groups: parasites and predators. The dominant species include Apanteles flavipes (Cameron), Sturmiopsis inferens Townsend and Trichogramma sp., which parasitize the sugarcane borer; Synonycha grandis (Thunberg), Lemnia biplagiata (Swartz), Cheilomenes sexmaculata (Fabricius) and Thiallela sp., which prey on Ceratovacuna lanigera Zehntner; and Euborellia pallipes Shiraki, Orius (Heterorius) minutus (Linnaeus) and Scymnus (Neopullus) hoffmanni Weise which preys on Saccharicoccus sacchari (Cocherell), Baliothrips serratus Kobus and Trochorhopalus humeralis Chevrolat. Protecting these natural enemies will encourage natural control of pest species while protecting the environment and maintaining ecological balance. Moreover, through enhanced comprehensive pest control, sustainable development of the sugar industry will be promoted. [ABSTRACT FROM AUTHOR]

Loss of cane and sugar yield caused by the combined occurrence of Tetramoera schistaceana (Snellen) and Chilo sacchariphagus (Bojer) were measured in pesticide-treated and untreated areas during 2014-2016. The results indicated that the in untreated areas, percent dead-heart was 8.30% - 58.83%, the percent stalk injured was 26.73% - 96.67%, the percent internodes bored was 4.40% - 25.87%, and the effective stem number was reduced by 4440-21900 stalk/ha. Measured yield and sugar yield loss results showed cane yield was reduced by 5.32-44.53 T/ha; the yield loss percent was5.92% - 44.53%; the sugarcane juice yield decreased by 1.73% - 3.28%; the sucrose content reduced by 0.33% - 5.63%; sugarcane brix dropped by 0.70-6.36 BX; the fibre and reducing sugar increased by 0.22% - 0.98% and 0.11%-1.58%, respectively. It was confirmed that in majority of sugarcane fields in Yunnan, China, T. schistaceana and C. sacchariphagus cause severe reduction of sugarcane and sugar yield. [ABSTRACT FROM AUTHOR]