Revision of the subfamily Opiinae (Hymenoptera,Braconidae) from Hunan (China), including thirty-six new species and two new genera

The species of the subfamily Opiinae (Hymenoptera: Braconidae) from Hunan (Oriental China) are revised and illustrated. Thirty-six new species are described: Apodesmia bruniclypealis Li & van Achterberg, sp. n., Apodesmia melliclypealis Li & van Achterberg, sp. n., Areotetes albiferus Li & van Achterberg, sp. n., Areotetes carinuliferus Li & van Achterberg, sp. n., Areotetes striatiferus Li & van Achterberg, sp. n., Coleopioides diversinotum Li & van Achterberg, sp. n., Coleopioides postpectalis Li & van Achterberg, sp. n., Fopius dorsopiferus Li, van Achterberg & Tan, sp. n., Indiopius chenae Li & van Achterberg, sp. n., Opiognathus aulaciferus Li & van Achterberg, sp. n., Opiognathus brevibasalis Li & van Achterberg, sp. n., Opius crenuliferus Li & van Achterberg, sp. n., Opius malarator Li, van Achterberg & Tan, sp. n., Opius monilipalpis Li & van Achterberg, sp. n., Opius pachymerus Li & van Achterberg, sp. n., Opius songi Li & van Achterberg, sp. n., Opius youi Li & van Achterberg, sp. n., Opius zengi Li & van Achterberg, sp. n., Phaedrotoma acuticlypeata Li & van Achterberg, sp. n., Phaedrotoma angiclypeata Li & van Achterberg, sp. n., Phaedrotoma antenervalis Li & van Achterberg, sp. n., Phaedrotoma depressiclypealis Li & van Achterberg, sp. n., Phaedrotoma flavisoma Li & van Achterberg, sp. n., Phaedrotoma nigrisoma Li & van Achterberg, sp. n., Phaedrotoma protuberator Li & van Achterberg, sp. n., Phaedrotoma rugulifera Li & van Achterberg, sp. n., Li & van Achterberg,Phaedrotoma striatinota Li & van Achterberg, sp. n., Phaedrotoma vermiculifera Li & van Achterberg, sp. n., Rhogadopsis latipennis Li & van Achterberg, sp. n., Rhogadopsis longicaudifera Li & van Achterberg, sp. n., Rhogadopsis maculosa Li, van Achterberg & Tan, sp. n., Rhogadopsis obliqua Li & van Achterberg, sp. n., Rhogadopsis sculpturator Li & van Achterberg, sp. n., Utetes longicarinatus Li & van Achterberg, sp. n. and Xynobius notauliferus Li & van Achterberg, sp. n. Areotetes van Achterberg & Li, gen. n. (type species: Areotetes carinuliferus sp. n.) and Coleopioides van Achterberg & Li, gen. n. (type species: Coleopioides postpectalis sp. n. are described. All species are illustrated and keyed. In total 30 species of Opiinae are sequenced and the cladograms are presented. Neopius Gahan, 1917, Opiognathus Fischer, 1972, Opiostomus Fischer, 1972, and Rhogadopsis Brèthes, 1913, are treated as a valid genera based on molecular and morphological differences. Opius vittata Chen & Weng, 2005 (not Opius vittatus Ruschka, 1915), Opius ambiguus Weng & Chen, 2005 (not Wesmael, 1835) and Opius mitis Chen & Weng, 2005 (not Fischer, 1963) are primary homonymsandarerenamed into Phaedrotoma depressa Li & van Achterberg, nom. n., Opius cheni Li & van Achterberg, nom. n. andOpius wengi Li & van Achterberg, nom. n., respectively. Phaedrotoma terga (Chen & Weng, 2005) comb. n.,Diachasmimorpha longicaudata (Ashmead, 1905) and Biosteres pavitita Chen & Weng, 2005, are reported new for Hunan, Opiostomus aureliae (Fischer, 1957) comb. n. is new for China and Hunan; Xynobius maculipennis(Enderlein, 1912) comb. n. is new for Hunan and continental China and Rhogadopsis longuria (Chen & Weng, 2005) comb. n. is new for Hunan. The following new combinations are given: Apodesmia puncta (Weng & Chen, 2005) comb. n., Apodesmia tracta (Weng & Chen, 2005) comb. n., Areotetes laevigatus (Weng & Chen, 2005) comb. n., Phaedrotoma dimidia (Chen & Weng, 2005) comb. n., Phaedrotoma improcera (Weng & Chen, 2005) comb. n., Phaedrotoma amputata (Weng & Chen, 2005) comb. n., Phaedrotoma larga (Weng & Chen, 2005) comb. n., Phaedrotoma osculas (Weng & Chen, 2005) comb. n., Phaedrotoma postuma (Chen & Weng, 2005) comb. n., Phaedrotoma rugulosa (Chen & Weng, 2005) comb. n., Phaedrotoma tabularis (Weng & Chen, 2005) comb. n., Rhogadopsis apii (Chen & Weng, 2005) comb. n., Rhogadopsis dimidia (Chen & Weng, 2005) comb. n., Rhogadopsis diutia (Chen & Weng, 2005) comb. n., Rhogadopsis longuria (Chen & Weng, 2005) comb. n., Rhogadopsis pratellae(Weng & Chen, 2005) comb. n., Rhogadopsis pratensis (Weng & Chen, 2005) comb. n., Rhogadopsis sculpta (Chen & Weng, 2005) comb. n., Rhogadopsis sulcifer (Fischer, 1975) comb. n., Rhogadopsis tabidula(Weng & Chen, 2005) comb. n., Xynobius complexus (Weng & Chen, 2005) comb. n., Xynobius indagatrix (Weng & Chen, 2005) comb. n., Xynobius multiarculatus (Chen & Weng, 2005) comb. n.The following (sub)genera are synonymised: Snoflakopius Fischer, 1972, Jucundopius Fischer, 1984, Opiotenes Fischer, 1998, and Oetztalotenes Fischer, 1998, with Opiostomus Fischer, 1971; Xynobiotenes Fischer, 1998, with Xynobius Foerster, 1862; Allotypus Foerster, 1862, Lemnaphilopius Fischer, 1972, Agnopius Fischer, 1982, and Cryptognathopius Fischer, 1984, with Apodesmia Foerster, 1862; Nosopoea Foerster, 1862, Tolbia Cameron, 1907, Brachycentrus Szépligeti, 1907, Baeocentrum Schulz, 1911, Hexaulax Cameron, 1910, Coeloreuteus Roman, 1910, Neodiospilus Szépligeti, 1911, Euopius Fischer, 1967, Gerius Fischer, 1972, Grimnirus Fischer, 1972, Hoenirus Fischer, 1972, Mimirus Fischer, 1972, Gastrosema Fischer, 1972, Merotrachys Fischer, 1972, Phlebosema Fischer, 1972, Neoephedrus Samanta, Tamili, Saha & Raychaudhuri, 1983, Adontopius Fischer, 1984, Kainopaeopius Fischer, 1986, Millenniopius Fischer, 1996, and Neotropopius Fischer, 1999, with Phaedrotoma Foerster, 1862.     

Phylogenetic utility of the nuclear genes AGAMOUS 1 and PHYTOCHROME B in palms (Arecaceae): an example within Bactridinae

Background and Aims

Molecular phylogenetic studies of palms (Arecaceae) have not yet provided a fully resolved phylogeny of the family. There is a need to increase the current set of markers to resolve difficult groups such as the Neotropical subtribe Bactridinae (Arecoideae: Cocoseae). We propose the use of two single-copy nuclear genes as valuable tools for palm phylogenetics.

Methods

New primers were developed for the amplification of the AGAMOUS 1 (AG1) and PHYTOCHROME B (PHYB) genes. For the AGAMOUS gene, the paralogue 1 of Elaeis guineensis (EgAG1) was targeted. The region amplified contained coding sequences between the MIKC K and C MADS-box domains. For the PHYB gene, exon 1 (partial sequence) was first amplified in palm species using published degenerate primers for Poaceae, and then specific palm primers were designed. The two gene portions were sequenced in 22 species of palms representing all genera of Bactridinae, with emphasis on Astrocaryum and Hexopetion, the status of the latter genus still being debated.

Key Results

The new primers designed allow consistent amplification and high-quality sequencing within the palm family. The two loci studied produced more variability than chloroplast loci and equally or less variability than PRK, RPBII and ITS nuclear markers. The phylogenetic structure obtained with AG1 and PHYB genes provides new insights into intergeneric relationships within the Bactridinae and the intrageneric structure of Astrocaryum. The Hexopetion clade was recovered as monophyletic with both markers and was weakly supported as sister to Astrocaryum sensu stricto in the combined analysis. The rare Astrocaryum minus formed a species complex with Astrocaryum gynacanthum. Moreover, both AG1 and PHYB contain a microsatellite that could have further uses in species delimitation and population genetics.

Conclusions

AG1 and PHYB provide additional phylogenetic information within the palm family, and should prove useful in combination with other genes to improve the resolution of palm phylogenies.     

On Hypolycaena from Maluku, Indonesia, including the first description of male Hypolycaena asahi (Lepidoptera, Lycaenidae)

The taxonomy and distribution of the five species of Hypolycaena in Maluku are discussed and new locality records given. Corrections are made to the published taxonomy and distribution of Hypolycaena phorbas (Fabricius, 1793). This clarification enables a better understanding of the biogeography of the genus. Hypolycaena asahi Okubo, 2007, was originally described from a single female from Ambon and is here recorded from Seram. The male is described for the first time.     

Natural Occurrence of Entomogenous Nematodes in Tennessee Nursery Soils

To isolate potential insect biocontrol agents, entomogenous nematodes were surveyed in Tennessee plant nurseries in 1991. Soil samples from 113 nursery sites were baited with greater wax moth (Galleria mellonella) larvae, house cricket (Acheta domesticus) adults, lesser mealworm (Alphitobius diaperings) adults, and house fly (Musca domestica) larvae. Heterorhabditis bacteriophora and Steinernema carpocapsae were each recovered from 17 soil samples. Heterorhabditis bacteriophora was more common in habitats with crape myrtle (Lagerstroemia indica) and Chinese juniper (Juniperus chinensis) than other nursery plants, and S. carpocapsae was more frequently recovered from habitats with juniper and Southern magnolia (Magnolia grandiflora). Bulk density, electrical conductivity, organic matter, pH, temperature, and moisture content of the entomogenous-nematode positive soil samples were compared. Other nematode genera recovered with insect baits included Rhabditis sp., Pelodera sp., Cryptaphelenchoides sp., and Mesodiplogaster sp., which was recovered from a greater percentage of soil samples than the other five genera.     

Distribution and Prevalence of Parasitic Nematodes of Cowpea (Vigna unguiculata) in Burkina Faso

A comprehensive survey of the plant parasitic nematodes associated with cowpea (Vigna unguiculata) production fields was carried out in the three primary agro-climatic zones of Burkina Faso in West Africa. Across the three zones, a total of 109 samples were collected from the farms of 32 villages to provide a representative coverage of the cowpea production areas. Samples of rhizosphere soil and samples of roots from actively growing cowpea plants were collected during mid- to late-season. Twelve plant-parasitic nematode genera were identified, of which six appeared to have significant parasitic potential on cowpea based on their frequency and abundance. These included Helicotylenchus, Meloidogyne, Pratylenchus, Scutellonema, Telotylenchus, and Tylenchorhynchus. Criconemella and Rotylenchulus also had significant levels of abundance and frequency, respectively. Of the primary genera, Meloidogyne, Pratylenchus, and Scutellonema contained species which are known or suspected to cause losses of cowpea yield in other parts of the world. According to the prevalence and distribution of these genera in Burkina Faso, their potential for damage to cowpea increased from the dry Sahelian semi-desert zone in the north (annual rainfall < 600 mm/year), through the north-central Soudanian zone (annual rainfall of 600-800 mm/year), to the wet Soudanian zone (annual rainfall ≥ 1000 mm) in the more humid south-western region of the country. This distribution trend was particularly apparent for the endoparasitic nematode Meloidogyne and the migratory endoparasite Pratylenchus.     

Ecological Study of Nematode Parasitism in Ips Beetles from California and Idaho

Nematodes found in Ips paraconfusus from ponderosa pine in California were an undescribed species of Parasitaphelenchus, Contortylenchus elongatus, C. reversus, and C. brevicomi. C. elongatus, the most commonly found contortylenchid, was present in 98.2% of the contortylenchid-parasitized beetles. Only one nematode parasite of the gut, a Parasitorhabditis sp., was isolated. Although significant differences in parasitism were observed, they were by collection sites, rather than by elevation or bole sources (slash or standing). Significant changes in parasitism between fall and spring collections were observed but not at every site. Nematode parasitism in the F₁ generation of I. paraconfusus by Parasitaphelenchus, Contortylenchus, or Parasitorhabditis increased or decreased from the parent generation depending upon the experiment.Nematode parasites from I. pini included an undescribed Parasitaphelenchus sp., two undescribed Contortylenchus spp., C. reversus and Parasitylenchus (= Neoparasitylenchus) ovarius from the hemocel, and Parasitorhabditis ipini from the gut. Parasitaphelenchus sp. was found in 99% and 45.3% of the beetles from Idaho and California, respectively. Of the 1,000 I. pini from Idaho and California, 157 were parasitized by the contortylenchid species or P. ovarius.     

A revision of the Chinese Trigonalyidae (Hymenoptera,Trigonalyoidea)

The Chinese fauna of the family Trigonalyidae Cresson, 1887, is revised, keyed and fully illustrated for the first time. Eight genera of this family (Bakeronymus Rohwer, 1922, Bareogonalos Schulz, 1907, Jezonogonalos Tsuneki, 1991, re-instated, Lycogaster Shuckard, 1841, Orthogonalys Schulz, 1905, Pseudogonalos Schulz, 1906, Taeniogonalos Schulz, 1906 and Teranishia Tsuneki, 1991) are recorded from China. The genus Ischnogonalos Schulz, 1907, is synonymized with Taeniogonalos Schulz, 1906. In total 40 valid species are recognized. Twenty species are new for science: Jezonogonalos elliptifera sp. n., J. jiangliae sp. n., J. luteata sp. n., J. nigrata sp. n., Lycogaster angustula sp. n., L. flavonigrata sp. n., L. nigralva sp. n., Orthogonalys cheni sp. n., O. clypeata sp. n., O. robusta sp. n., Pseudogonalos angusta sp. n., Taeniogonalos bucarinata sp. n., T. cordata sp. n., T. geminata sp. n., T. sculpturata sp. n., T. triangulata sp. n., T. tricolorisoma sp. n., T. uncifera sp. n., Teranishia crenulata sp. n. and T. glabrata sp. n. Two species are reported new for China: Orthogonalys elongata Teranishi, 1929 and Nanogonalos flavocincta Teranishi, 1929 (renamed to Taeniogonalos subtruncata nom. n.). Seven new synonyms are proposed: Poecilogonalos yuasai Teranishi, 1938, and P. maga taiwana Tsuneki, 1991, of Taeniogonalos taihorina (Bischoff, 1914); Taiwanogonalos minima Tsuneki, 1991, and T. similis Tsuneki, 1991, of Taeniogonalos alticola (Tsuneki, 1991); P. intermedia Chen, 1949, and P. unifasciata Chen, 1949, of Taeniogonalos formosana (Bischoff, 1913). Six taxa are recognised as valid species: Bakeronymus seidakka Yamane & Terayama, 1983, Jezonogonalos laeviceps (Tsuneki, 1991), J. satoi (Tsuneki, 1991), Taeniogonalos alticola (Tsuneki, 1991), T. flavoscutellata (Chen, 1949) and T. gestroi (Schulz, 1908). Five new combinations are made: Jezonogonalos laeviceps (Tsuneki, 1991), comb. n., J. satoi (Tsuneki, 1991), comb. n., Taeniogonalos flavoscutellata (Chen, 1949), comb. n., T. gestroi (Schulz, 1908), comb. n. and T. lachrymosa (Westwood, 1874), comb. n. Lectotypes are designated for Lycogaster violaceipennis Chen, 1949, Poecilogonalos flavoscutellata Chen, 1949, P. rufofasciata Chen, 1949, and P. tricolor Chen, 1949.     

Morphological Comparison and Taxonomic Utility of Copulatory Structures of Selected Nematode Species

Spicules of 9 Meloidogyne, 2 Heterodera, 3 Globodera, and 12 other plant-parasitic, insect-parasitic, and free-living nematodes were excised and examined using scanning electron microscopy (SEM). Gubernacula of some of the species were also excised, and their structure was determined. The two spicules of all species examined were symmetrically identical in morphology. The spicule typically consisted of three parts: head, shaft, and blade with dorsal and ventral vela. The spicular nerve entered through the cytoplasmic core opening on the lateral outer surface of the spicule head and generally communicated with the exterior through one or two pores at the spicule tip. Spicules of Xiphinema sp. and Aporcelaimellus sp. were not composed of three typical parts, were less sclerotized, and lacked a cytoplasmic core opening and distal pores. Spicules of Aphelenchoides spp. had heads expanded into apex and rostrum and had very arcuate blades with thick dorsal and ventral edges (limbs). Gubernaculum shapes were stable within a species, but differed among species examined. The accessory structures of Hoplolaimus galeatus consisted of a tongue-shaped gubernaculum with two titillae at its distal end and a plate-like capitulum terminating distally in two flat, wing-like structures. A comparison of spicules of several species of Meloidogyne by SEM and light microscopy revealed no striking morphological differences.     

A molecular phylogeny and classification of Leptochloa (Poaceae: Chloridoideae: Chlorideae) sensu lato and related genera

Background and Aims

Leptochloa (including Diplachne) sensu lato (s.l.) comprises a diverse assemblage of C₄ (NAD-ME and PCK) grasses with approx. 32 annual or perennial species. Evolutionary relationships and a modern classification of Leptochloa spp. based on the study of molecular characters have only been superficially investigated in four species. The goals of this study were to reconstruct the evolutionary history of Leptochloa s.l. with molecular data and broad taxon sampling.

Methods

A phylogenetic analysis was conducted of 130 species (mostly Chloridoideae), of which 22 are placed in Leptochloa, using five plastid (rpL32-trn-L, ndhA intron, rps16 intron, rps16-trnK and ccsA) and the nuclear ITS 1 and 2 (ribosomal internal transcribed spacer regions) to infer evolutionary relationships and revise the classification.

Key results

Leptochloa s.l. is polyphyletic and strong support was found for five lineages. Embedded within the Leptochloa sensu stricto (s.s.) clade are two Trichloris spp. and embedded in Dinebra are Drake-brockmania and 19 Leptochloa spp.

Conclusions

The molecular results support the dissolution of Leptochloa s.l. into the following five genera: Dinebra with 23 species, Diplachne with two species, Disakisperma with three species, Leptochloa s.s. with five species and a new genus, Trigonochloa, with two species.     

Fruit load modulates flowering-related gene expression in buds of alternate-bearing ‘Moncada’ mandarin

Background and Aims

Gene determination of flowering is the result of complex interactions involving both promoters and inhibitors. In this study, the expression of flowering-related genes at the meristem level in alternate-bearing citrus trees is analysed, together with the interplay between buds and leaves in the determination of flowering.

Methods

First defruiting experiments were performed to manipulate blossoming intensity in ‘Moncada’ mandarin, Citrus clementina. Further defoliation was performed to elucidate the role leaves play in the flowering process. In both cases, the activity of flowering-related genes was investigated at the flower induction (November) and differentiation (February) stages.

Key Results

Study of the expression pattern of flowering-genes in buds from on (fully loaded) and off (without fruits) trees revealed that homologues of FLOWERING LOCUS T (CiFT), TWIN SISTER OF FT (TSF), APETALA1 (CsAP1) and LEAFY (CsLFY) were negatively affected by fruit load. CiFT and TSF activities showed a marked increase in buds from off trees through the study period (ten-fold in November). By contrast, expression of the homologues of the flowering inhibitors of TERMINAL FLOWER 1 (CsTFL), TERMINAL FLOWER 2 (TFL2) and FLOWERING LOCUS C (FLC) was generally lower in off trees. Regarding floral identity genes, the increase in CsAP1 expression in off trees was much greater in buds than in leaves, and significant variations in CsLFY expression (approx. 20 %) were found only in February. Defoliation experiments further revealed that the absence of leaves completely abolished blossoming and severely affected the expression of most of the flowering-related genes, particularly decreasing the activity of floral promoters and of CsAP1 at the induction stage.

Conclusions

These results suggest that the presence of fruit affects flowering by greatly altering gene-expression not only at the leaf but also at the meristem level. Although leaves are required for flowering to occur, their absence strongly affects the activity of floral promoters and identity genes.     

Resistance of Auto- and Allotetraploid Triticeae Species and Accessions to Meloidogyne chitwoodi based on Genome Composition

The Columbia root-knot nematode Meloidogyne chitwoodi parasitizes several plant species, including grasses that have been developed for semiarid environments, and substantially reduces the productivity of cereals and the longevity of perennial grasses growing under semiarid conditions throughout the intermountain region. Thirty-two auto- and allotetraploid (2n = 28) taxa in the perennial Triticeae were evaluated as possible sources of resistance to M. chitwoodi. Low levels of root galling were observed on roots of all accessions; root-gall indices ranged from 0 (no galls) to 1.95 in the grasses compared to 4.67 for the susceptible ''Ranger'' alfalfa check on a scale of 1 to 6. Even though the gall ratings were low, significant (P < 0.01) differences among accessions of the same species, among species, and among genera with different genomes were observed. Within the reproductive indices, which ranged from 0.01 to 1.20 in the grasses compared to 65.38 for the alfalfa check, there was no difference among genera with different genomes and accessions within the same species and genome; however, there was a significant (P < 0.05) difference among species with the same genomes. This variation can be traced to Thinopyrum nodosum (Jaaska-19), which was the only accession with a reproductive factor greater than 1.00. Based on the data, all auto- and allotetraploids are considered resistant to M. chitwoodi.     

Agriculturally-polluted Irrigation Water as a Source of Plant-Parasitic Nematode Infestation

Water from a major irrigation canal and water from a deep well was used to irrigate plants growing in methyl bromide fumigated screenhouse ground beds. Nematode populations in these beds were compared during three seasons of continuous cropping to alfalfa, bean, eggplant, mint, sugarbeet, or wheat. Beds irrigated with canal water became heavily infested with a variety of plant parasitic nematodes while those receiving well water did not.     

Nematode Control Related to Fusarium Wilt in Soybean and Root Rot and Zinc Deficiency in Corn

Nematode and disease problems of irrigated, double-cropped soybean and corn, and zinc deficiency of corn were investigated. Ethylene dibromide, phenamiphos, and aldicarb were equally effective for controlling nematodes and increasing yields of corn planted minimum-till and soybean planted in a moldboard plow prepared seedbed. The residual effects on yields of nematicides applied to the preceeding crop occurred during 3 years for soybean and 1 year for corn. Fusarium wilt symptoms of soybean that developed during 2 years of the study were less severe in all nematicide-treated plots than in control plots. Typical zinc deficiency symptoms on 30-day-old corn plants were observed during 1 year of the study in certain plots. Symptoms were not evident on plants grown on plots treated with ethylene dibromide, and only occasional plants had symptoms on plots treated with phenamiphos and aldicarb. The amount of yield response directly related to nematode control could not be determined because of the apparent interaction of nematodes on the expression of Fusarium wilt of soybean. Our study strongly indicates that the expression of Fusarium wilt of soybean and zinc deficiency in corn are influenced by nematodes and that nematicides will reduce their severity.     

Role of Nematodes,Nematicides, and Crop Rotation on the Productivity and Quality of Potato,Sweet Potato,Peanut, and Grain Sorghum

The objective of this experiment was to determine the effects of fenamiphos 15G and short-cycle potato (PO)-sweet potato (SP) grown continuously and in rotation with peanut (PE)-grain sorghum (GS) on yield, crop quality, and mixed nematode population densities of Meloidogyne arenaria, M. hapla, M. incognita, and Mesocriconema ornatum. Greater root-gall indices and damage by M. hapla and M. incognita occurred on potato than other crops. Most crop yields were higher and root-gall indices lower from fenamiphos-treated plots than untreated plots. The total yield of potato in the PO-SP and PO-SP-PE-GS sequences increased from 1983 to 1985 in plots infested with M. hapla or M. arenaria and M. incognita in combination and decreased in 1986 to 1987 when root-knot nematode populations shifted to M. incognita. The total yields of sweet potato in the PO-SP-PE-GS sequence were similar in 1983 and 1985, and declined each year in the PO-SP sequence as a consequence of M. incognita population density increase in the soil. Yield of peanut from soil infested with M. hapla increased 82% in fenamiphos-treated plots compared to untreated plots. Fenamiphos treatment increased yield of grain sorghum from 5% to 45% over untreated controls. The declining yields of potato and sweet potato observed with both the PO-SP and PO-SP-PE-GS sequences indicate that these crop systems should not be used longer than 3 years in soil infested with M. incognita, M. arenaria, or M. hapla. Under these conditions, these two cropping systems promote a population shift in favor of M. incognita, which is more damaging to potato and sweet potato than M. arenaria and M. hapla.     

Description of Trilineellus clathrocutis n.g., n.sp. (Tylenchorhynchinae: Tylenchida Thorne, 1949) with a Key to Species and Observations on Tylenchorhynchus sensu stricto

TrilineeIlus clathrocutis n.g., n.sp. is described and illustrated. It was found as an associate of corn (Zea mays) in Stockton, Georgia, USA, and is related to a group of Tylenchorhynchus sensu lato species having three lines in nonareolated lateral fields. This new species is closely related to Tylenehorhynehus divittatus Siddiqi 1961, T. sculptus Seinhorst 1963, and T. triglyphus Seinhorst 1963 (syn. T. chonai Sethi & Swarup 1968) Tarjan 1973. It differs from these species primarily by having longitudinal striae on the body. These four species are differentiated from Tylenchorhynchus sensu stricto by having three lateral lines instead of four. They differ from Uliginotylenchus Siddiqi 1971 by having nonareolated lateral fields, fewer than 25 annules on conoid rounded tails, differently shaped gubernacula, nonattenuated stylets, and other distinctive characters. They differ from Triversus Sher 1973 by having the male tail enclosed by the bursa and by having rounded female tails. SEM observations of T. clathrocutis reveal a cuticle deeply cut by longitudinal and horizontal striae and bearing wide (> 2.0 μm) annules. Trilineellus is proposed to accommodate the new species and the three-incisured species still within Tylenchorhynchus. Tylenchorhynchus is thereby the repository for species within Tylenchorhynchinae having four lines in the lateral field, no conspicuous labial disc, and bursa enclosing the male tail.