SummaryThe root-lesion nematode, Pratylenchus thornei, attacks a wide range of crops and causes significant reductions in global grain production. Breeding programmes are currently restricted to using parents with moderate resistance to P. thornei as cereal cultivars with complete resistance are yet to be identified. This study evaluated 484 of CIMMYT’s spring wheat accessions for resistance to P. thornei of which 56 lines were pre-identified as resistant under controlled growth room conditions. These lines were further evaluated for their resistance and tolerance reactions under field conditions, where 14 accessions maintained their resistance and 16 were moderately resistant against P. thornei. Four lines gave excellent resistant and tolerance reactions to P. thornei. The relationship between the nematode reproduction factor (Pf/Pi) and wheat grain yield in field experiments fits a linear regression model. These findings could be useful for improving P. thornei resistance in wheat.

The cereal cyst nematode, Heterodera filipjevi (Madzhidov) Stelter, was detected in Turkey in 1996 and since then it has been increasingly reported to cause losses in wheat yields. Cereal cyst nematode populations have a wide genetic diversity which makes it difficult to be managed. The objectives of this research were to investigate the genetic variation of 23 cyst nematode populations collected from wheat growing areas of Bolu Province, utilising sequenced ITS-rDNA regions, and monitoring main nematode isolate population dynamics in field conditions. The results of ribosomal DNA sequencing revealed that all cyst populations were H. filipjevi and that little genetic variation was present among populations. The highest number of second-stage juveniles was observed between April and beginning of May in a field experiment; white females were visible on the roots in late May. The hatching process was positively correlated with low temperatures, but there were inverse correlations between reproductive factors and initial nematode population densities.

IntroductionThe root lesion nematodes (Pratylenchus spp.; RLNs) rank third behind root-knot (Meloidogyne spp.) and cyst nematodes (Heterodera spp. and Globodera spp.) in greatest economic impact in crops worldwide. Pratylenchus spp. are migratory endoparasites of several economically important crops in various climatic regions (Castillo and Vovlas, 2007), including Turkey (Kepenekci, 2012). Their ability to reproduce within host root tissues enables them to survive unfavorably dry conditions, when other soilinhabiting nematodes are limited by soil water availability (Vanstone et al., 1998).Field symptoms associated with Pratylenchus species are nonspecific and can be confused with the symptoms of other disease-causing agents, nutritional deficiencies, or water shortage (Castillo and Vovlas, 2007). Infested roots with RLNs show dead cortical and epidermal cells and loss of lateral roots and root hairs (Vanstone et al., 1998). Generally, invaded plants appear dwarfed with premature yellowing of older leaves, and many other growth parameters are negatively affected (Smiley et al., 2004). These symptoms are similar to those caused by nutrient deficiencies (Taylor et al., 1999) or by other fungal root rot diseases (Taheri et al., 1994), which makes their diagnosis hard in the field. Detecting and correctly identifying nematode species is the first step in managing their spread and preventing economic damage, yet morphological identification of Pratylenchus species is time-consuming and requires specialized expertise. It is therefore easier and more accurate to use molecular techniques such as biotechnological tools (Al-Banna et al., 2004), in particularly DNA-based techniques that have been designed to differentiate among different Pratylenchus species (Al-

The Mediterranean cereal cyst nematode, Heterodera latipons, is an important plant parasitic nematode that negatively impacts cereal production worldwide, particularly in the Mediterranean Basin. Successful control of cereal cyst nematodes requires knowledge of the nematode species/pathotypes and their biology. However, little information is currently available concerning the phenotypic and genotypic variability of H. latipons populations in Turkey. This study analyzed the morphological/morphometric and genetic characteristics of Turkish H. latipons populations to define intraspecific distinctions between them. Morphological and morphometric studies focused on the pattern of the perineal region of cysts and second stage juveniles (J2), while the molecular analyses used sequenced ITS-rDNA regions targeting the internal transcribed spacer (ITS) region of rDNA. The data from these investigations demonstrate that nematode populations from Adana and Hatay provinces differ from the populations collected in Kilis, Gaziantep, and Mardin provinces. These phenotypic and genotypic differences between H. latipons populations may indicate that they are heterogenic, with at least two pathotypes. To date, this study is the most comprehensive analysis identifying H. latipons populations in major wheatproducing areas of Turkey.

Agricultural fields usually contain both plant parasitic and beneficial free-living nematodes. Plant parasitic nematodes have a negative impact on plant productivity and quality traits, whereas free-living nematodes can have beneficial effects on the agricultural soils health. This study was conducted to investigate the diversity of both plant parasitic nematodes and beneficial free-living nematode. Soil samples were collected in 2015 from wheat growing areas of Bolu Province to investigate soil nematode diversity. Bolu Province was divided into two sub-areas according to elevational. Forty-three nematode taxa were found in the samples; 13 taxa plant parasites, 12 bacterivores, 4 fungivores, 10 omnivores and 4 predators. Relative distribution of nematode trophic groups indicated a bacterivore dominated community, followed by plant parasites, fungivores and omnivores; predators represented only a small proportion. Free-living nematodes, especially bacterivores of basal fauna members and large bodied omnivore members were in good condition in abundance and diversity. General community and maturity indices were calculated for each sample and for the two sub-areas. They produced narrow range values with no significant differences. The study revealed that soil food web in wheat growing areas of the province was in fair to good condition based on nematode diversity. ÖzetTarım arazileri hem bitki paraziti nematodlar hem de serbest yaşayan yararlı nematodları birlikte barındırmaktadır. Bitki paraziti nematodlar bitki kalite parametreleri üzerinde olumsuz etkiler doğururken, serbest yaşayan nematodlar ise yaşamsal faaliyetleri sonucu olumlu etkilere sahiptir. Dolayısıyla, çalışma hem bitki paraziti nematodların çeşitlilik yapısı hem de yararlı nematodların çeşitlilik yapısını incelemek üzere yürütülmüştür. Bu amaçla, 2015 yılında Bolu ili buğday alanlarından toprak örnekleri toplanmıştır. Bolu ili rakım farklılıkları göz önüne alınarak iki farklı alt-bölgeye ayrılmıştır. Çalışma alanında, 13 bitki paraziti, 12 bakterivor, 4 fungivor, 4 predatör ve 10 omnivor gruba ait olmak üzere, toplam 43 nematod taksonu tespit edilmiştir. Nematod trofik gruplarının oransal dağılımlarına göre, bakterivorların baskın olduğu bir kommunite yapısına sahip olduğunu, bunu bitki parazitleri, fungivorlar, omnivorlar izlemiş, predatörler ise oldukça düşük bir orana sahip olduğu saptanmıştır. Serbest yaşayan nematodlardan, özellikle temel fauna bileşeni olan bakterivor ve iri cüsseli omnivore nematodların hem çeşitlilik hem de yoğunluk bakımından iyi durumda olduğu görülmüştür. Genel kommunite ve nematode maturity indisleri her iki altbölgeden alınan toprak örnekleri için hesaplanmış, indis değerleri arasında ise istatistikî olarak bir farklılığın görülmediği, dar bir aralıkta dağıldığı saptanmıştır. Çalışma sonuçlarına göre, nematode biyoçeşitlilik yapısına dayanılarak elde edilen bilgiler ışığında, Bolu ili buğday alanlarındaki toprak besin ağı orta ve iyi dereceler arasında yer aldığı sonucuna varılmıştır.