Transcriptomic data creation: Two year old ramets of compatible and incompatible Eucalyptus grandis genotypes were grown in a field cage insectarium. After four months these E. grandis clones were split into uninfested and infested groups comprising three biological replicates of six plants each. Infestation with L. invasa was natural and total RNA was extracted after seven days from leaf gall tissue. Total RNA was then submitted to Beijing Genomics Institute (BGI) for RNA sequencing with 50 bp paired end reads. (Compatible clone: GC540;Incompatible clone: TAG5)
Pathogen Biology: Leptocybe invasa, or more commonly known as the gall-forming wasp, is an insect-pest of Eucalyptus spp. This species thought native to Australia has now distributed globally and can be found in Asia, Europe, Africa and America, totaling 29 countries (Mendel et al., 2004a; Zheng et al., 2014). These insects are capable of travelling great distances with the example of the first occurrence in South Africa. L. invasa was first detected in Africa in Algeria in 2002 (Mendel et al., 2004a), and travelled south across the continent to South Africa where it was found in 2007 (Dittrich-Schröder et al., 2009). These insects cause disease when ovipositing on leaf and stem tissues, by laying their eggs in the upper epidermal layer of young leaves (Mendel et al., 2004a). Typical symptoms of Eucalyptus stem and leaf attack by L. invasa include bump-shaped galls on the leaf midribs, petioles and stems of several Eucalyptus spp. (Neser et al., 2007). L. invasa is controlled through chemical insecticides as well as several biological control agents, such as, a Selitrichodes (Eulophidae), two species of Megastigmus (Torymidae) and one Quadrastichus (Eulophidae) (Zheng et al., 2014).
Transcriptomic data creation: Compatible third generation Eucalyptus nitens seedling stems were inoculated with Phytophthora cinnamomi (isolate CMW26310) and mock-inoculated with sterile cV8 agar plugs. Three biological replicates which consisted of inoculated and mock-inoculated samples were created by pooling six trees per biological replicate. Total RNA was extracted at 24hr post inoculation (hpi), 48 hpi, 96 hpi, and 1 week post inoculation (wpi) and submitted to Beijing Genomics Institute (BGI) for RNA sequencing with 50 bp paired end reads.
Pathogen Biology: Phytophthora cinnamomi, commonly known as the root rot pathogen, is a devastating and highly-successful pathogen. Phytophthora cinnamomi was first isolated in 1922 in Sumatra, where it was causing disease on cinnamon trees. However, the pathogen has a wide host range and is thought to infect as many as 3000 species of plants. Phytophthora cinnamomi has been found on every major continent, excluding Antarctica adding to this pathogens fame. Phytophthora cinnamomi is a fungus-like microbe as it has the ability to produce biflagellate motile-zoospores which are not characteristic of fungal classes. These zoospores utilize their flagella, to swim to root wounds via chemotaxic attraction to chemical and electrical gradient stimulus. Infection by Phytophthora cinnamomi, causes stem cankers, root rot and results in stunted growth, dieback and death in severe infections.
Transcriptomic data creation: Compatible and incompatible genotypes of E. grandis ramets were split into control and treated groups. The control and treated groups consisted of three ramets each. Control ramets were mock-inoculated with sterile 2% MEA agar plugs, while inoculated ramets were challenged with the fungal pathogen C. austroafricana isolate CMW2113. Total RNA was extracted after 3 days and samples were sent to the Beijing Genome Institute (BGI) for RNA-Sequencing with 50 bp paired end reads. (Compatible clone: ZG14;Incompatible clone: TAG5)
Pathogen Biology: C. austroafricana is the causal agent of stem-canker disease of Eucalyptus spp. C austroafricana is known to occur natively on Myrtaceae in Southern Africa, as well as on native Melastomataceae in South America and South-eastern Asia. C. austroafricana is known to infect trees of the genus of Eucalyptus spp., Tibouchina spp. and Syzygium spp. Infection by C. austroafricana results in a plethora of symptoms including branch die-back, branch cracking and cankers, cankers found at the bases often results in tree death. Cankers that form on the stem of Eucalyptus spp. are associated with wounding or lesions. This pathogen has been shown to have undergone a host shift to infect non-native Eucalyptus spp.