Faruk Akyazi

Interspecific nematode signals regulate dispersal behavior.

Background Dispersal is an important nematode behavior. Upon crowding or food depletion, the free living bacteriovorus nematode Caenorhabditis elegans produces stress resistant dispersal larvae, called dauer, which are analogous to second stage juveniles (J2) of plant parasitic Meloidogyne spp. and infective juveniles (IJ)s of entomopathogenic nematodes (EPN), e.g., Steinernema feltiae. Regulation of dispersal behavior has not been thoroughly investigated for C. elegans or any other nematode species. Based on the fact that ascarosides regulate entry in dauer stage as well as multiple behaviors in C. elegans adults including mating, avoidance and aggregation, we hypothesized that ascarosides might also be involved in regulation of dispersal behavior in C. elegans and for other nematodes such as IJ of phylogenetically related EPNs. Methodology/Principal Findings Liquid chromatography-mass spectrometry analysis of C. elegans dauer conditioned media, which shows strong dispersing activity, revealed four known ascarosides (ascr#2, ascr#3, ascr#8, icas#9). A synthetic blend of these ascarosides at physiologically relevant concentrations dispersed C. elegans dauer in the presence of food and also caused dispersion of IJs of S. feltiae and J2s of plant parasitic Meloidogyne spp. Assay guided fractionation revealed structural analogs as major active components of the S. feltiae (ascr#9) and C. elegans (ascr#2) dispersal blends. Further analysis revealed ascr#9 in all Steinernema spp. and Heterorhabditis spp. infected insect host cadavers. Conclusions/Significance Ascaroside blends represent evolutionarily conserved, fundamentally important communication systems for nematodes from diverse habitats, and thus may provide sustainable means for control of parasitic nematodes.

Pasteuria penetrans suppression of root-knot nematode Meloidogyne arenaria race 1 in vegetables

Bu calismanin amaci, obligat parazit olan Pasteuria penetrans bakterisinin sebze yetistirilen alanlarda kok-ur nematodu Meloidogyne arenaria irk 1’e karsi baskinligini ortaya cikarmak, bu baskinligin etkisinin kirilmasina neden olan diger kok-ur nematod turlerinin alanda bulunup bulunmadigini tespit etmektir. Bu amacla 2011 yilinin Mart ayinda, daha onceden P. penetrans bulastirilmis ve M. arenaria race 1’e karsi baskin oldugu bilinen Florida Universitesi’nin arastirma arazisinde, domates Lycopersicon lycopersicum cv. Bella Rosa, salatalik Cucumis sativus L. cv. Cobra, bamya Abelmoschus (=Hibiscus) esculentus (L.) cv. Clemson Spineless ve kabak Cucurbita pepo L. cv. Golden Summer gibi dort farkli sebze cesidi yetistirilmeye baslanmistir. Calisma bolunmus parseller deneme deseninde 8 tekerrurlu olarak yurutulmustur. Her bir sebze cesidi icin biri ilacli digeri ilacsiz olacak sekilde parseller hazirlanmistir. Ilacli parseller 112 lt/ha oraninda 1,3-dichloropropene (1,3-D) (Telone II) ile ilaclanmistir. Tum deneme parsellerinden hasat sonunda bitki kokleri ve toprak ornekleri alinarak inceleme yapilmistir. Alinan toprak orneklerinden elde edilen M. arenaria irk 1 juvenillerinin P. penetrans’in endosporlari ile bulasiklik orani en yuksek %40 olarak kimyasal uygulanmis kabak parselinde, en dusuk endospor bulasiklik orani ise kimyasal uygulanmayan bamya parselinde yaklasik %10 olarak gozlenmistir. Deneme alanlarinda yetistirilen sebzelerden yalnizca domates bitkisi koklerinde cok dusuk oranda diger nematode turlerinden M. incognita tespit edilmistir. Calismadan elde edilen sonuclar, sebzelerde M. arenaria race 1 tarafindan meydana gelen zararin azaltilmasinda ve bu nematodun baski altinda tutulmasinda P. penetrans’in onemli bir etmen oldugunu ortaya koymusturThis study was conducted to determine the suppressiveness of obligat parasite P. penetrans against the peanut root-knot nematode Meloidogyne arenaria race 1 in vegetable growing site and to find out whether the field site have infested with other root-knot nematode species, causing the suppression to break down. The study were carried out at four vegetable crops grown sites tomato Lycopersicon lycopersicum cv. Bella Rosa, cucumber Cucumis sativus L. cv. Cobra, okra Abelmoschus (=Hibiscus) esculentus (L.) Moench cv. Clemson Spineless and squash Cucurbita pepo L. cv. Golden Summer at the Plant Science Research and Education Unit-Citra, University of Florida, US. The field site was arranged in a split plot design with eight replicates. To determine the effect of 1,3dichloropropene (1,3-D) on P. penetrans, the split plot was fumigated with 1,3-D (Telone II)at dose of 112 L/ha.. Plant and soil samples were collected from each plot at harvest time. The percentages of M. arenaria race 1 infective juvenile (J2) with endospores attached ranged from 40%to 10%.. Only a very low incidence of M. incognita was extracted from tomato roots galls.. The results indicate that P. penetrans is likely to be one of the important effective agent in the nematode suppression and the reduction M. arenaria race 1 damage..