A Pyrimidin-Like Plant Activator Stimulates Plant Disease Resistance and Promotes the Synthesis of Primary Metabolites

Plant activators are chemicals that induce plant defense responses to various pathogens. Here, we reported a new potential plant activator, 6-(methoxymethyl)-2-[5-(trifluoromethyl)-2-pyridyl] pyrimidin-4-ol, named PPA2 (pyrimidin-type plant activator 2). Unlike the traditional commercial plant activator benzothiadiazole S-methyl ester (BTH), PPA2 was fully soluble in water, and it did not inhibit plant growth or root system development in rice (Oryza sativa). PPA2 pretreatment significantly increased plant resistance against bacterial infection in both Arabidopsis and rice, in conjunction with increases in the level of jasmonoyl-isoleucine and 12-oxo-phytodienoic acid. In addition, metabolite profiling indicated that BTH significantly reduced the abundance of various primary metabolites in rice seedlings, including most amino acids, sugars, and organic acids; by contrast, PPA2 promoted their synthesis. Our results thus indicate that PPA2 enhances plant defenses against bacterial infection through the jasmonic acid pathway, and that as a water-soluble compound that can promote the synthesis of primary metabolites it has broad potential applications in agriculture.

Control of pepper bacterial spot and tomato bacterial speck using bactericides in combination with a plant activator

The efficacy of a formulated product of tea tree oil (TTO) and a standard copper based bactericide in combinations with acibenzolar-S-methyl (ASM) for control of bacterial spot of pepper and bacterial speck of tomato was evaluated under controlled conditions. Treatments with copper hydroxide+ASM at both application rates and TTO+ASM showed the best efficacy in control of bacterial spot disease in pepper plants (with respective efficacy values 83.5%, 83.7 % and 86.9%). Similar efficacy was achieved by treatment with copper hydroxide alone (82.2%). On the other hand, the efficacy of TTO, applied alone, was significantly lower at both rates (63.8% and 71.5%) in bacterial spot control in pepper. The same treatments (copper hydroxide +ASM at both application rates and TTO+ASM) were most efficient in suppressing the causal agent of bacterial speck disease in tomato (87%, 82.3% and 81.6%). The efficacy of treatment with the standard bactericide copper hydroxide, applied alone, was significantly lower compared to its combination with ASM (79.1%). Similarly to the bacterial spot experiment, TTO treatments alone showed lower, although satisfactory efficacy at both application rates (66.1% and 68.9%). The results of this study showed that combination of the bioactive compound - ASM with either the standard copper hydroxide bactericide or TTO significantly improved their efficacy in both bacterial spot and speck disease control, and thus implied that combining different biorational compounds, such as essential oils and bioactive products, with standard copper treatments and their inclusion into integrated management programs are of essential importance for the control of bacterial diseases of pepper and tomato.

Stimulant effect of plant activator BION on photosynthesis and its inhibitory effect on pathogenic fungi

Spraying of wheat seedlings with aqueous preparations of CGA 245704 (BION) caused a slight decrease in chlorophyll content accompanied by the stable increase in the rate of O₂ evolution per chlorophyll. Stimulant effect of BION on photosynthetic activity depended on both the ai concentration and number of treatments. Biophysical methods based on the registration of slow fluorescence induction and thermoluminescence of wheat leaves revealed the stimulation of photosystem II activity and the increase in the rate of electron transport between the photosystems in treated plants. It is also shown that BION itself can show a partial fungitoxic activity because it slowed down the germination of Erysiphe graminis f.sp. tritici fungi. This is obviously the reason for partial protective effect of BION when it was applied after the inoculation of wheat seedlings with the pathogen.

Distribution and pathogenic peculiarities of fungi of the Alternaria genus on vegetable crops in Lithuania

In 1999–2001 the investigation of Alternaria species on vegetable crops: cabbage, cucumber, tomato and carrot was carried out and fungi species were isolated from vegetables and substrata used for plant cultivation. Isolated micromycetes: Alternaria alternata, Alternaria tenuissima, Alternaria brassicae, Alternaria brassicicola, Alternaria cucurbitae, Alternaria dauci, Alternaria radicina and Alternaria solani differed in pathogenic peculiarities, frequency of occurrence and their various reaction to fungicides (a.s. azoxystrobin, dichlofluanid, Cooper hydroxide, mancozeb, propamocarb hydrochloride), plant activator Bion (benzothadiazole) and antagonistic microorganisms (Trichoderma harzianum, Streptomyces griseoviridis).