Abstract. Sanjaya IPW, Sukma D, Sudarsono, Chan MT. 2020. Effect of genotype, concentration and timing of salicylic acid application to Phalaenopsis against Dickeya dadantii infection. Biodiversitas 21: 4317-4323. Soft-rot because of Dickeya dadantii (Dd) infection is one of the most difficult to control, affecting the cultivation of Phalaenopsis in tropical regions. Salicylic acid (SA) is known as an inducer of resistance against pathogens in some plant species. The study aim to identify the effects of genotypes, concentrations, and timing of salicylic acid application to Phalaenopsis against D. dadantii inoculation. In experiment 1, eight Phalaenopsis genotypes were treated by SA at doses of 0 and 60 ppm and then inoculated with D. dadantii. At a dose of 60 ppm, SA did not increase the resistance to D. dadantii in any genotypes. In experiment 2, a representative of a very susceptible genotype (P. amabilis) was treated with high SA concentrations (60, 360, and 720 ppm). The results demonstrated that at SA concentrations of 360 and 720 ppm, slightly increase P. amabilis resistance to D. dadantii. In experiment 3, the most effective SA concentration (720 ppm) was used at 2, 3, 5, or 7 days after SA treatment. The timing of the SA application did not affect the resistance of P. amabilis to D. dadantii. The present study shows that SA concentrations up to 60 ppm did not inhibit D. dadantii infection. Nevertheless, such inhibition was observed at a high SA dose (720 ppm) for a short period.
Orchids (Phalaenopsis) are ornamental plants that are cultivated commercially and in great demand in the market. Soft-rot disease (SRD) caused by the necrotrophic pathogen Dickeya dadantii is a cause of considerable economic loss to cultivators of many orchid species. Our previous experiment identified a limited number of species that were resistant to D. dadantii. This study aimed to validate the resistance level of four Phalaenopsis species in a detached leaf inoculation protocol to identify the resistance mechanism(s) involved. Soft-rot symptom diameter was measured from 6 to 18 hours post-inoculation (HPI) with D. dadantii. Disease assessment confirmed that P. amboinensis is a resistant species, P. pantherina is a susceptible species, and P. amabilis and P. schilleriana are very susceptible species. There was no difference in the lignin content between the resistant and very susceptible species. Detailed observation of resistant and very susceptible species, P. amboinensis vs. P. amabilis, revealed higher phenylalanine ammonia-lyase (PAL) and peroxidase (POD) in P. amabilis than in P. amboinensis. In contrast, there was higher salicylic acid (SA) content in P. amboinensis than in P. amabilis. These results suggest that POD and PAL activities may not be effective in defense against soft-rot disease, while SA plays an important role in the resistance of P. amboinensis to D. dadantii. Low PAL activity in P. amboinensis implies that the SA contents from the isochorismate pathway may be involved in the mechanism of P. amboinensis resistance to D. dadantii. Therefore, endogenous SA content may be a good indicator for screening resistant species in Phalaenopsis.
One of the modern plant breedings through genetic engineering is Agrobacterium tumefaciens-mediated transformation. Agrobacterium tumefaciens-mediated transformation can be performed in vitro or in planta. In planta transformation arises from the weaknesses of the in vitro method such as need high hygiene standard, professional tissue culture experts, and more time to prepare explants and somaclonal variation. In planta transformation is a method to transfer the gene to the plant genome without any tissue culture stages. The aims of this research were to know the possibility of the prick and soak in planta method with the target of tomato seeds and to know the most suitable inoculation time for tomato seeds transformation by prick and soak method the transformation is done by pricking the seeds and soaking them in the A. tumefaciens suspension. The treatments in this study were 1 and 2 days inoculation time to test the efficacy of prick and soak in planta transformation method. Tomato seeds were pricked with a needle on the center once, and then soaked in A. tumefaciens strain LB4404 suspension carrying pKYS-SoSPS1 plasmid with Neomycin Phosphotransferase (NPTII) and Saccharum officinarum Sucrose Phosphate synthase (SoSPS1) genes. Visualization of tomato’s DNA samples after PCR showed that 1-day inoculation sample was positively integrated with NPTII gene and negative in the 2 days inoculation treatment.
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