Search

The induction of natural defense mechanisms in plants is considered to be one of the most important strategies used in integrated pest management (IPM). Plant immune inducers could reduce the use of chemicals for plant protection and their harmful impacts on the environment. Planticine® is a natural plant defense biostimulant based on oligomers of α(1→4)-linked D-galacturonic acids, which are biodegradable and nontoxic. The aim of this study was to define the molecular basis of Planticine’s biological activity and the efficacy of its use as a natural plant resistance inducer in greenhouse conditions. Three independent experiments with foliar application of Planticine® were carried out. The first experiment in a climatic chamber (control environment, no pest pressure) subjected the leaves to RNA-seq analysis, and the second and third experiments in greenhouse conditions focused on efficacy after a pest infestation. The result was the RNA sequencing of six transcriptome libraries of tomatoes treated with Planticine® and untreated plants; a total of 3089 genes were found to be differentially expressed genes (DEGs); among them, 1760 and 1329 were up-regulated and down-regulated, respectively. DEG analysis indicated its involvement in such metabolic pathways and processes as plant-pathogen interaction, plant hormone signal transduction, MAPK signaling pathway, photosynthesis, and regulation of transcription. We detected up-regulated gene-encoded elicitor and effector recognition receptors (ELRR and ERR), mitogen-activated protein kinase (MAPKs) genes, and transcription factors (TFs), i.e., WRKY, ERF, MYB, NAC, bZIP, pathogenesis-related proteins (PRPs), and resistance-related metabolite (RRMs) genes. In the greenhouse trials, foliar application of Planticine® proved to be effective in reducing the infestation of tomato leaves by the biotrophic pathogen powdery mildew and in reducing feeding by thrips, which are insect herbivores. Prophylactic and intervention use of Planticine® at low infestation levels allows the activation of plant defense mechanisms.

Hyacinth (Hyacinthus orientalis) bulbs infected by Fusarium oxysporum showed the symptoms of gummosis. The purpose of this study was to clarify the hormonal regulation of gummosis and composition of gums from hyacinth bulbs. The application of ethephon (2-chloroethylphosphonic acid), an ethylene-releasing compound, at 2% (w/w, in lanolin) induced gummosis in hyacinth bulbs. Methyl jasmonate (JA-Me) at 1.5% (w/w, in lanolin) induced gummosis as well. Simultaneous application of JA-Me and ethephon further enhanced gummosis. Molecular mass distribution of hyacinth gums analyzed by gel permeation chromatography indicated that the gums were mainly homogenous polysaccharides with an average molecular weight of ca. 30kDa. Analysis of the sugar composition of the gums after hydrolysis revealed that the majority were arabinose (ca. 35%) and galactose (ca. 40%) together with small amounts of fucose, rhamnose and uronic acids (ca. 5%, respectively), suggesting that the gums are pectic arabinogalactans. These results indicate that jasmonates (JAs) interact with ethylene to stimulate sugar metabolism, producing pectic arabinogalactans, and vice versa, leading to gummosis. These findings, together with those from our previous studies in tulips (Tulipa gesneriana) and grape hyacinth (Muscari armeniacum), revealed that sugar metabolism and hormonal regulation relating to gummosis are different among species of bulbous plants.

Summary The effect of gums formed in stone-fruit trees on the in vitro growth and development of Verticillium albo-atrum and V. dahliae cultured on Czapek Dox Agar (CzDA), Malt Extract Agar (MEA) and Potato Dextrose Agar (PDA) was investigated. Addition of gums at concentration 5 mg/cm³ to all used media greatly stimulated mycelium growth of V. albo-atrum and V. dahliae and sporulation of the pathogen. Surface of colony of the pathogens after 8 days of culturing on CzDA, MEA and PDA supplemented with gums increased twice on the first two media and three fold on PDA as compare to the control.

The knowledge about the role of jasmonates in ethylene production by pathogenic fungi is ambiguous. In this study, we describe the effect of methyl jasmonate (JA-Me) and gums formed in stone fruit trees on the growth and in vitro ethylene production by mycelium of Verticillium dahliae and Alternaria alternata. Methyl jasmonate at concentrations of 100, 250 and 500 μg·cm-3 inhibited the mycelium growth of V. dahliae and A. alternata, proportionally to the concentrations used. After 8 days of incubation, JA-Me at concentration of 500 μg·cm-3 limited the area of mycelium of these pathogens by 7-8 times but did not entirely inhibited the pathogen growth. Addition of gums produced by trees of cherry and peach to a medium containing 40 μg·cm-3 JA-Me did not influence the mycelium growth of V. dahliae, but gums of plum and apricot trees stimulated mycelium growth, in comparison to JA-Me only. Methyl jasmonate at concentrations of 2 and 40 μg·cm-3 stimulated the ethylene production by mycelium of V. dahliae and A. alternata. It is possible that methyl jasmonate stimulated ethylene production in mycelium of these pathogens through interaction with some fractions of galactans formed during hydrolysis of agar. The lack of interaction of JA-Me with polysaccharides of stone fruit trees gums concerning ethylene production was documented and it needs further explanation.

It is well known that Fusarium oxysporum f. sp. tulipae (Fot), ethylene and jasmonates have a promoting effect on gum induction and its accumulation in tulip (Tulipa gesneriana L.) bulbs. The induction and production of gums are suggested to be regulated by a signal network of jasmonates and ethylene, especially by cross-talk between them. Tulip gums consist of glucuronoarabinoxylan with an average molecular weight of approximately 700 kDa. In this review some biological activity of tulip gums is presented. It is believed that gums have a function in limiting the spread of fungal and bacterial pathogens and insects by isolating the infected tissues. It was found that the addition of tulip gums at a concentration of 5 mg•cm3 to Czapek-Dox-Agar, Malt-Extract-Agar and Potato-Dextrose-Agar greatly stimulated mycelium growth of Fusarium oxysporum f. sp. tulipae and sporulation of the pathogen. Addition of tulip gums to the Czapek-Dox-Broth caused that the pathogen secreted the polysaccharide gum degrading enzymes. In further studies it was found that tulip gums induced by Fusarium oxysporum f. sp. tulipae, ethylene or jasmonates elicited red coloured secondary metabolite(s) in mycelium of the pathogen. The effect of homogenate of different tulip organs (scales, leaves, stem, pistils and roots), applied alone and simultaneously with tulip gums, on red pigment formation by mycelium of F. oxysporum f. sp. tulipae was investigated. It is interesting that a homogenate of tulip scales and pistils almost totally inhibited the formation of the red coloured pigment induced by tulip gums in the mycelium of Fot. It is possible that the polysaccharide of tulip gums, which is glucuronoarabinoxylan, may act as an elicitor that regulates some physiological and biochemical processes connected or responsible for mycelium growth of the Fusarium oxysporum f. sp. tulipae and induction of secondary metabolites by mycelium of the pathogen.

The effect of D,L-β-aminobutyric acid (BABA) on the growth and development of the root system and the development of fusariosis on tulip bulbs cv. Apeldoorn infected by Fusarium oxysporum f. sp. tulipae (F.ox.t. 218) was studied. The length and fresh weight of roots, the development of fusariosis on bulbs and the linear growth of mycelium of F.ox.t. 218 on PDA medium were measured. Preventively used BABA at a concentration of 100, 250 and 300 µg·cm-3 for soaking uncooled and cooled tulip bulbs greatly inhibited the development of fusariosis on the root system; the length and fresh weight of roots were similar to those of the bulbs not inoculated with F.ox.t. 218. At a concentration of 100 µg·cm-3;, BABA used for soaking bulbs limited the development of fusariosis on scales in about 50% and the concentration of 200 µg·cm-3 totally inhibited the disease symptoms induced by F.ox.t. 218. At a concentration of 100 - 1000 µg·cm-3, BABA did not inhibit the mycelium growth of F.ox.t. 17 and F.xo.t. 218 on PDA medium. This study suggests that BABA protects tulip roots and bulb scales against F. oxysporum f. sp. tulipae by inducing resistance in these organs and has no direct influence on the pathogen.

In the present work it was shown that total saponins originated from M. hybrida and M. sativa substantially limited mycelium growth of F. oxysporum f. sp. tulipae and symptoms of fusariosis on tulip bulbs. Out of 15 individual tested saponins originated from M. arabica, M. hybrida and M. sativa, four compounds: 3-O-[β-D-glucopyranosyl (1→2)α-L-arabinopyranosyl] hederagenin, hederagenin 3-O-β-D-glucopyranoside, medicagenic acid, medicagenic acid 3-O-β-D-glucopyranoside had the strongest inhibitory effect on mycelium growth of Fusarium oxysporum f. sp. tulipae on PDA medium. The total saponins from M. arabica, M. hybrida and M. sativa inhibited the number of colony forming units of Fusarium oxysporum f. sp. tulipae in artificially infested substrate. The use of saponins originated from Medicago as a fungicide is suggested.

The aim of this work was to determine the casual agents of leaf spotting occurring on Curcuma alismatifolia Gagnep and possible methods of thir control. Symptoms of dry brown spots were observed on the leaves, stems and lower side of perianth of C. alismatifolia growing in greenhouse conditions. Pathogenicity tests with isolates obtained from diseased plants. Showed that Acremonium sp. was the main cause of disease symptoms on turmeric. The fungicides such as piraklostrobin (Signum 33 WG), fenhexamid (Teldor 500 SC), tiofanat-methyl (Topsin 500 M) and grapefruit extract (Biosept Active), greatly inhibited the growth and development of Acremonium sp. An application of piraklostrobin at the concentration of 250 μg/cm3 completely inhibited the mycelium growth. Grapefruit extract, fenhexamid and tiofanat-methyl at the concentration of 250 μg/cm3 limited the mycelium growth in 70, 75, and 80% respectively. Preventiv and curative treatments of piraklostrobin, grapefruit extract, fenhexamid and tiofanat-methyl significantly reduced the development Acremonium sp.