Gracilacus

Abstract: Morphological and morphometric analyses were conducted on the genus Paratylenchus, based on documented data in the literature and characters of Iranian populations of twelve species, including P. arculatus, P. colinus, P. conicephalus, P. coronatus, P. neoamblycephalus, P. neoprojectus, P. obtusicaudatus, P. paraperaticus, P. similis, P. straeleni, P. variabilis and P. veruculatus. Moreover, males of P. obtusicaudatus are described for the first time and additional data provided for males of P. paraperaticus. The variability of the most important taxonomic characters for species identification in the genus was estimated by calculation of coefficient of variation (CV) for 49 species and the ratio of extremes in the range of measured females (max/min ratios) for 82 species of the genus, based on 66 and 170 populations, respectively. A list of 117 valid species of Paratylenchus is provided, along with a dichotomous identification key and a diagnostic compendium.

Abstract: This is the first detailed report on plant-parasitic nematodes occurring in Idaho and eastern Oregon, U.S.A. Plant-parasitic nematodes from 186 soil samples collected in 26 counties were identified. Twenty-five nematode genera were found. Forty-seven species including two evidently undescribed are reported in the region for the first time. The new records are in 11 genera: Criconemella, Geocenamus, Gracilacus, Hemicycliophora, Helicotylenchus, Merlinius, Paratylenchus, Pratylenchus, Trophonema, Trophurus, and Tylenchorhynchus. Other nematode genera found were Anomyclus, Aphelenchoides, Aphelenchus, Coslenchus, Ditylenchus, Heterodera, Hoplolaimus, Megadorus, Meloidogyne, Paratrichodorus, Psilenchus, Trichodorus, Tylenchus, and Xiphinema.

Abstract: Over 70 species, belonging to 33 genera, of plant parasitic nematodes have been reported in association with olive. Several species of Helicotylenchus have been observed to cause root necrosis and considered capable of affecting olive tree growth. Three species of Meloidogyne (M. incognita, M. lusitanica and M. javanica) were responsible for heavy galling and growth retardation in inoculation trials and natural infestation. Pratylenchus vulnus has been demonstrated in inoculation trials as a potential pathogen of olive. Xiphinema species commonly occur around olive roots and X. elongatum has been shown to affect olive plant growth. Several sedentary plant nematodes attack olive. Tylenchulus semipenetrans infects olive in California (US) and Italy. Trophotylenchulus saltensis was described from olive roots in Jordan and a cyst nematode, Heterodera mediterranea, was shown to feed and multiply on olive roots. The cortical feeding cells of roots fed upon by Gracilacus peratica showed thickened and lignified wall near the penetration points of the stylet and those exposed to Ogma rhombosquamatum also presented hypertrophic nuclei and nucleoli. Rotylenchulus macrodoratus induces the formation of an enlarged mononucleate stelar or cortical ‘nurse cell’ with dense cytoplasm and hypertrophic nucleolus.

Abstract: Ten species of Paratylenchus and six of Gracilacus are discussed. P. italiensis, P. tateae and P. labiosus are synonymized with P. similis. Measurements of specimens from various populations are presented, and previously published morphometric data compiled in tables to characterise known limits of species variation. The significance of morphology of males and juveniles in identification of these nematodes is shown in descriptions of various species. It is demonstrated that in G. macrodora the third stage juvenile lacks a stylet, while the fourth stage juvenile has a well developed stylet and oesophagus and apparently feeds. G. bilineata sp. n. from Taiwan has only two incisures, lips not protruding, stylet 46 (43-50) μm, V = 73-78, no vulval flaps, and males with very thin stylet. G. vera sp. n. from Mexico is characterized by having sublateral lips projected anteriorly, four incisures, stylet 78 (66-86) μm, V = 76-79, small vulval flaps, and males without stylets.