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Odziv entomopatogenih ogorčic (Rhabditida: Steinernematidae in Heterorhabditidae) na izbrane kemične snovi
Ipavec, Neža (Author), Laznik, Žiga (Mentor) More about this mentor... This link opens in a new window

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Abstract
Entomopatogene ogorčice (EPO) se uporabljajo v programih biotičnega varstva rastlin. Z namenom optimizacije njihove rabe smo preučevali kemotropizem infektivnih ličink (IL) entomopatogenih ogorčic Steinernema feltiae, S. carpocapsae, S. kraussei in Heterorhabditis bacteriophora na hlapne organske snovi (HOS). V raziskavo smo vključili 6 HOS, ki jih izločajo poškodovane korenine črne gorjušice (Brassica nigra L.); dimetil sulfid [DMS], dimetil disulfid [DMDS], dimetil trisulfid [DMTS], alil izotiocianat [AITC], feniletil izotiocianat [FEITC] in benzonitril [BN]. Do poškodb korenin črne gorjušice je prišlo zaradi hranjenja žerk (ličink) kapusove muhe (Delia radicum [L.]). Predvidevali smo, da je kemotropizem EPO do preučevanih HOS pogojen z vrsto EPO in njihovo strategijo iskanja gostitelja ter z vrsto HOS. Na vse omenjene parametre pa bi vplivala tudi temperatura in čas izpostavljenosti HOS. Laboratorijski poskus v petrijevkah, ki smo jih prelili z agarjem, smo izvajali pri dveh preučevanih temperaturah (20 in 25 °C) in 75 % relativni zračni vlagi. Gibanje IL smo preverjali po 4 in 24 urah. Na podlagi podatkov smo izračunali kemotropični indeks, ki nam je pokazal ali določena snov deluje na EPO kot atraktant (privabilno), repelent (odvračalno) oz. nima vpliva. Rezultati naše raziskave so pokazali, da je bila vrsta S. kraussei najbolj mobilna. Več kot 35 % IL se je pri temperaturi 20 °C premaknilo iz osrednjega dela petrijevke proti zunanjemu. Gibanje preostalih vrst EPO je bilo manj izrazito. Ugotovili smo, da je gibanje EPO v največji meri odvisno od temperature. Pri temperaturi 25 °C je bilo gibanje EPO bolj izrazito. Vrednosti kemotropičnega indeksa so v naši raziskavi pokazale, da vse HOS delujejo odvračalno na EPO vrste S. kraussei pri obeh preučevanih temperaturah. Podatki nakazujejo, da HOS, ki bazirajo na žvepleni osnovi (sulfidi) in na razgradnih produktih glukozinolatov (izotiocianati, benzonitril), vplivajo na gibanje EPO in imajo pomembno vlogo pri posredni obrambi rastlin pred škodljivci.

Language:Slovenian
Keywords:entomopatogene ogorčice, Steinernema, Heterorhabditis, kemotropizem
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:BF - Biotechnical Faculty
Year:2017
Publisher:[N. Ipavec]
UDC:632.937.1:631.467:632.651:581.5(043.2)
COBISS.SI-ID:8790137 Link is opened in a new window
Views:586
Downloads:408
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Secondary language

Language:English
Title:Response of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) to selected chemical compounds
Abstract:
Entomopathogenic nematodes (EPNs) are organisms that can be used in biological control programs for plant protection. In order to optimize their use we studied chemotropism of infective juveniles (IJs) of EPNs Steinernema feltiae, S. carpocapsae, S. kraussei and Heterorhabditis bacteriophora to volatile compounds (VOCs). The study included 6 VOCs secreted by Brassica nigra L. roots; dimethyl sulfide [DMS], dimethyl disulfide [DMDS], dimethyl trisulfide [DMTS], allyl isothiocyanate [AITC], phenylethyl isothiocyanate [PITC], and benzonitrile [BN]). Damage of B. nigra roots was caused by cabbage fly (Delia radicum [L.]) larvae. We hypothesized that attraction behavior exhibited by the EPNs toward the tested VOCs could be related to the species and would vary with foraging strategy, VOC, time of exposure and temperature. The chemotaxis assay was performed under laboratory conditions in Petri dishes, which contained agar. Experiment was conducted at two studied temperatures (20 and 25 °C) and 75 % relative humidity. The movement of IJs was observed after 4 and 24 hrs. Based on our results we calculated chemotaxis index with aim to determine if VOC is attractant, repellent or has no effect on EPNs. Results of our investigation showed that S. kraussei was the most mobile species in our assay, and at 20 °C, more than 35 % of S. kraussei IJs moved to the outer circles of the Petri dishes. Movement of other EPNs species was less prominent. The movement of different EPN species towards VOCs was influenced by temperature. At higher temperature (25 °C) the movement was more prominent. The chemotaxis index values showed, that all of the VOCs tested in our assay repelled S. kraussei at both experimental temperatures, suggesting that sulfur compounds (sulfides) and glucosinolate breakdown products (isothiocyanate and benzonitrile) could play an important role in EPNs navigation and in indirect defense of plants against pests.

Keywords:entomopathogenic nematodes, Steinernema, Heterorhabditis, chemotropism

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