Phytoplasmas that infect gramineous plants, including Napier grass stunt, sugarcane whiteleaf, sugarcane grassy shoot, and Bermuda grass whiteleaf, have been classified into two closely related groups, 16SrXI and 16SrXIV, based on the 16S ribosomal RNA (rRNA) gene. Subsequently, phytoplasmas associated with coconut and Areca palm in southern India and Sri Lanka have been added into the 16SrXI group. However, the 16S rRNA gene gives relatively poor resolution between these phytoplasmas. In this study, a new set of universal phytoplasma primers that amplify approximately 1 kb of the leucyl transfer RNA synthetase (leuS) gene have been validated on a broad range of phytoplasma taxonomic groups. These have been used along with partial sequences of the secA gene to clarify the taxonomic classification of 16SrXI and 16SrXIV phytoplasmas. Based on this data, the sugarcane whiteleaf and grassy shoot phytoplasmas appear to be the same phytoplasma. The Napier grass stunt phytoplasma forms a distinct group from the Bermuda grass whiteleaf and sugarcane phytoplasmas, suggesting that Napier grass stunt should be in its own ‘Candidatus Phytoplasma sp.’. The phytoplasmas associated with coconut and arecanut in southern India and Sri Lanka, which are in the same 16SrXI group, appear in different groups based on secA analysis.

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Trichoderma spp. are effective biocontrol agents for a number of soil-borne plant pathogens. Some isolates are also known for their ability to induce systemic resistance in plants against different foliar pathogens. Induction of systemic resistance against Uromyces appendiculatus, the causal agent of bean rust, by Trichoderma spp. has not been reported. T. harzianum RU01 consistently triggered a significant (P = 0.05) degree of protection against rust in bean (Phaseolus vulgaris cv. Keppetipola Nill) under greenhouse conditions. Control efficacy was similar to that of rhizobacterium, Pseudomonas aeruginosa KMPCH, a test strain included in this study, which previously demonstrated induction of systemic resistance in bean. Given the spatial separation of challenging pathogen and biocontrol agent, this effect can be attributed to the induction of systemic resistance by T. harzianum RU01.

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