The citrus industry is severely affected by citrus black spot (CBS), a disease caused by the pathogen Phyllosticta citricarpa. This disease causes loss of production, decrease in the market price of the fruit, and reduction in its export to the European Union. Currently, CBS disease is being treated in orchards with various pesticides and fungicides every year. One alternative to CBS disease control without harming the environment is the use of microorganisms for biological control. Diaporthe endophytica and D. terebinthifolii, isolated from the medicinal plants Maytenus ilicifolia and Schinus terebinthifolius have an inhibitory effect against P. citricarpa in vitro and in detached fruits. Moreover, D. endophytica and D. terebinthifolii were transformed by Agrobacterium tumefaciens for in vivo studies. The transformants retained the ability to control of phytopathogenic fungus P. citricarpa after transformation process. Furthermore, D. endophytica and D. terebinthifolii were able to infect and colonize citrus plants, which is confirmed by reisolation of transformants from inoculated and uninoculated leaves. Light microscopic analysis showed fungus mycelium colonizing intercellular region and oil glands of citrus, suggesting that these two new species are capable of colonizing citrus plants, in addition to controlling the pathogen P. citricarpa.
This review provides an overview of our understanding of citrus plant immunity, focusing on the molecular mechanisms involved in the interactions with viruses, bacteria, fungi, oomycetes and vectors related to the following diseases: tristeza, psorosis, citrus variegated chlorosis, citrus canker, huanglongbing, brown spot, post-bloom, anthracnose, gummosis and citrus root rot.
Phytophthora nicotianae is a plant pathogen responsible for damaging crops and natural ecosystems worldwide. P. nicotianae is correlated with the diseases: citrus gummosis and citrus root rot, and the management of these diseases relies mainly on the certification of seedlings and eradication of infected trees. However, little is known about the infection strategies of P. nicotianae interacting with citrus plants, which rises up the need for examining its virulence at molecular levels. Here we show an optimized method to genetically manipulate P. nicotianae mycelium. We have transformed P. nicotianae with the expression cassette of fluorescence protein DsRed. The optimized AMT method generated relatively high transformation efficiency. It also shows advantages over the other methods since it is the simplest one, it does not require protoplasts or spores as targets, it is less expensive and it does not require specific equipment. Transformation with DsRed did not impair the physiology, reproduction or virulence of the pathogen. The optimized AMT method presented here is useful for rapid, cost-effective and reliable transformation of P. nicotianae with any gene of interest.
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