Effect of simultaneous and sequential inoculations of <Emphasis Type="Italic">Meloidogyne incognita</Emphasis>, <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> and <Emphasis Type="Italic">Phomopsis vexans</Emphasis> on eggplant in sand mix and fly ash mix soil

Effects simultaneous and sequential inoculations of Meloidogyne incognita, Ralstonia solanacearum and Phomopsis vexans were studied on the growth, chlorophyll and carotenoid contents of eggplants grown in 25% fly ash and 25% sand mix soil. Plants grown in 25% fly ash mix soil had lesser plant growth than grown in 25% sand ash mix soil. Inoculation of M. incognita / R. solanacearum or P. vexans caused reduction in plant growth, chlorophyll and carotenoid contents in both types of soils but these pathogens in combination caused a greater reduction in than individual inoculation. Inoculation of M. incognita 20 days prior to R. solanacearum caused a greater reduction in plant growth than inoculation of M. incognita prior to P. vexans. Inoculation of P. vexans prior to R. solanacearum caused a lesser reduction in plant growth, chlorophyll and carotenoid contents than inoculation of P. vexans prior to M. incognita. Inoculation of R. solanacearum 20 days prior to M. incognita caused a greater reduction in plant growth, chlorophyll and carotenoid contents than inoculation of R. solanacearum prior to P. vexans. Galling and multiplication of M. incognita was higher in plants grown in 25% sand amended soil than with 25% fly ash soil. R. solanacearum and P. vexans had adverse effects on galling and nematode multiplication. Wilt and blight indices caused by R. solanacearum and P. vexans were 3 respectively. Wilt and blight indices were 4 when two pathogens were inoculated together.     

Host-delivered RNAi-mediated root-knot nematode resistance in <Emphasis Type="Italic">Arabidopsis</Emphasis> by targeting <Emphasis Type="Italic">splicing factor</Emphasis> and <Emphasis Type="Italic">integrase</Emphasis> genes

Root-knot nematodes (RKNs) are one of the most important biotic factors limiting crop productivity in many crop plants. The major RKN control strategies include development of resistant cultivars, application of nematicides and crop rotation, but each has its own limitations. In recent years, RNA interference (RNAi) has become a powerful approach for developing nematode resistance. The two housekeeping genes, splicing factor and integrase, of Meloidogyne incognita were targeted for engineering nematode resistance using a host-delivered RNAi (HD-RNAi) approach. Splicing factor and integrase genes are essential for nematode development as they are involved in RNA metabolism. Stable homozygous transgenic Arabidopsis lines expressing dsRNA for both genes were generated. In RNAi lines of splicing factor gene, the number of galls, females and egg masses was reduced by 71.4, 74.5 and 86.6%, respectively, as compared with the empty vector controls. Similarly, in RNAi lines of the integrase gene, the number of galls, females and egg masses was reduced up to 59.5, 66.8 and 63.4%, respectively, compared with the empty vector controls. Expression analysis revealed a reduction in mRNA abundance of both targeted genes in female nematodes feeding on transgenic plants expressing dsRNA constructs. The silencing of housekeeping genes in the nematodes through HD-RNAi significantly reduced root-knot nematode infectivity and suggests that they will be useful in developing RKN resistance in crop plants.     

Resistance to root-knot nematodes on passion fruit genotypes in Brazil

With the expansion of passion fruit cultivation in Brazil, phytosanitary problems have increased, among them, the occurrence of root-knot nematodes. This research aimed to study the response of passion fruit genotypes to Meloidogyne incognita, M. javanica and M. enterolobii in addition to evaluating the life cycle of M. enterolobii in the passion fruit genotype ‘FB 200’. The genotype response was carried out in a greenhouse. Each pot’s soil was inoculated with 5000 eggs. Gall index, egg mass index and nematode reproduction factors were evaluated at 120 days after inoculation. All genotypes studied were resistant to M. incognita, M. javanica and M. enterolobii, except ‘Roxinho do Kênia’, which was susceptible to the three nematode species. The life cycle of M. enterolobii in “FB 200” passion fruit was studied in a growth chamber at 26 °C with a photoperiod of 12 h. Seven days after transplantation, each plant was inoculated with approximately 400 second-stage juveniles. Evaluations were done at 7, 14, 21, 28, 35, 42 and 49 days post inoculation. The nematode did not complete its life cycle.     

Population dynamics of <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> on cucumber grafted onto the Cucurbita hybrid RS841 or ungrafted and yield losses under protected cultivation

The influence of the squash hybrid RS841 rootstock (Cucurbita maxima x C. moschata) on population dynamics of Meloidogyne incognita and yield of cucumber cv. Dasher II was assessed during 2013 and 2014 in a plastic greenhouse. In addition, the relationship between ecophysiological parameters (plant water status, gas exchange, and leaf reflectance) and Pi and cucumber yield were also estimated in 2013. Nematode densities were determined at the beginning (Pi) and at the end (Pf) of each crop, and the relationship between these parameters was used to estimate the maximum multiplication rate (a), the maximum population density (M) and the equilibrium density (E) per grafted and ungrafted cucumber and cropping season. Moreover, the relationship between the multiplication rate (Pf/Pi) and Pi was compared between grafted and ungrafted cucumber per cropping season. Finally, the relative yield of grafted or ungrafted cucumber was plotted against Pi to determine the tolerance limit (T) and the minimum relative yield (m) by the Seinhorst damage function model. Values of a, M and E in grafted cucumber were higher than in ungrafted one irrespective of the cropping season. These results were supported by comparing the relationship between Pf/Pi and Pi between grafted and ungrafted cucumber. The relationship between Pi and yield fitted the Seinhorst damage function. The values of T and m did not differ between grafted and ungrafted each year. Predawn water potential, net photosynthetic rate, and leaf chlorophyll index decreased with increasing Pi. In addition, relative yield was related to variation in net photosynthetic rate and the leaf chlorophyll index. Under the conditions of this study, RS841 rootstock was neither resistant nor tolerant to M. incognita.     

Efficacy of a formulated product containing <Emphasis Type="Italic">Quillaja saponaria</Emphasis> plant extracts for the control of root-knot nematodes

The nematicidal effect of a formulated product containing extract from Quillaja saponaria was evaluated against the root-knot nematodes. The product QL Agri® 35 (QL) was tested to record the effect on second stage juveniles motility, egg hatch and also against field populations in greenhouse experiments contacted in three different locations of Greece. Convulsive movement of second stage juveniles of Meloidogyne incognita was recorded after exposure for 8 days at a series of doses, while the most paralyzed juveniles were counted at the dose of 8 mg l^?1. There was also a gradual decrease in the number of juveniles emerging from egg masses of the same nematode species when the dose of Q. saponaria was increased from 0 to 8 mg l^?1. In greenhouse experiments, the use of Q. saponaria could control root-knot nematodes and prevent nematodes increase in soil. The present study demonstrates that the use of Q. saponaria extract has the ability to control root-knot nematodes. Control given by Q. saponaria in field populations infecting cucumber was similar to that of cadusafos (Rugby®) and oxamyl (Vydate®) under the tested dosages and the specific conditions of the experiments.     

Inheritance of resistance to <Emphasis Type="Italic">Meloidogyne enterolobii</Emphasis> and individual selection in segregating populations of <Emphasis Type="Italic">Psidium</Emphasis> spp

Interaction between the phytonematode Meloidogyne enterolobii and the fungus Fusarium solani has caused direct and indirect losses in the entire guava production chain and consequent extermination of guava plantations throughout Brazil. The combined action of these two pathogens is known as “guava decline”. In order to obtain and assess Psidium spp. interspecific hybrids for resistance to the nematode M. enterolobii, interspecific crosses of P. guineense (susceptible araçá) x P. cattleyanum (resistant araçá); P.guineense (susceptible araçá) x P. guajava (susceptible guava) and P. cattleyanum (resistant araçá) x P. guajava (susceptible guava) were conducted. These crosses resulted in hybrid immune, susceptible and resistant to Meloidogyne enterolobii. The chi-square test rejected the hypothesis of monogenic inheritance with incomplete dominance, which corroborates that this trait has polygenic action. Predictions of genetic values ??and parameters were obtained by the REML / BLUP procedure, at individual level. Finally, the 30 selected individuals (immune and resistant) were obtained, which will be backcrossed with guava for the recovery of the agronomic traits desired and subsequent release of a new cultivar.     

Influence of different compositae on population density ofPratylenchus penetrans and some other root-infesting nematodes

Field and pot experiments with over 35 different Compositae, mainly perennial and annual flower crops, show thatHelenium hybrids,Gaillardia hybrid ‘Burgunder’ andEriophyllum caespitosum, in addition toTagetes patula ‘Harmony’, suppress populations ofPratylenchus penetrans very effectively. In other genera of Compositae species also occur which are poor hosts ofP. penetrans, although their suppressive action is generally significantly less marked than that of the species mentioned. Within the same plant genus considerable differences in host suitability were found. These results may prove to be useful in providing indications as to the most suitable sequence of crops for the control ofP. penetrans in nurseries of perennial crops, parks and gardens. Some data collected on host suitability of Compositae toRotylenchus robustus andTylenchorhynchus dubius show differences, though less marked than those relating toP. penetrans.     

Disease resistance in Vicia faba and Phaseolus vulgaris

Droplets of spore suspensions of each of four isolates ofBotrytis cinerea but not those of each of four isolates ofB. fabae proved to contain an antifungal compound 24 h after application on pod tissue ofVicia faba. Partial inhibition of germ-tube growth of three highly pathogenic isolates ofB. fabae was caused at 2.5 times the concentration of inhibitor needed to cause similar inhibition of each isolate ofB. cinerea and a weakly pathogenic isolate ofB. fabae. After extraction, concentration and chromatographic separation, 5–10 times more inhibitor was obtained from lesions in pods caused byB. cinerea than from those caused byB. fabae. However, the amounts of inhibitor extracted from whole leaves bearing either large lesions caused byB. fabae or small lesions caused byB. cinerea were almost the same. It is suggested that infection by either fungus induces inhibitor formation, but thatB. fabae metabolizes the inhibitor to an inactive form.No relation was found between amounts of an inhibitor produced in droplets of spore suspensions 24 h after application on pods of differential varieties ofPhaseolus vulgaris and the disease reactions caused by races ofColletotrichum lindemuthianum. Each race appeared to have a similar sensitivity to the inhibitor. Anatomical studies showed that only superficial growth of germ-tubes occurred in seed cavities in the first two days, after which penetration took place. Resistant or susceptible reactions were distinguished after 6 days in young pods, and even later in old pods. Before rejecting the hypothesis that the inhibitor may have a role in the mechanism of disease resistance, amounts of inhibitor in and around infection sites on leaves or stems should be measured. Apparent protection of leaf areas against infection was caused by prior inoculation with a race which was avirulent on the leaf. This phenomenon is consistent with the action of an inhibitor of the type found in pod tissues, but could be caused by reactions as yet unknown.     

The potential of entomopathogenic fungi to control the lettuce root aphid,<Emphasis Type="Italic">pemphigus bursarius</Emphasis>

The lettuce root aphid,Pemphigus bursarius, is a commercially important pest of lettuce and occupies a niche amenable to the action of entomopathogenic fungi. As the first stage of a biological control programme, a bioassay was developed against adult apterousP. bursarius. An isolate ofMetarhizium flavoviride was pathogenic toP. bursarius and sporulated abundantly upon aphid cadavers. However, two isolates ofVerticillium lecanii, pathogenic against glasshouse whitefly and aphids, were only weakly pathogenic toP. bursarius.     

Morphological and molecular characterisation of <Emphasis Type="Italic">Ditylenchus stenurus</Emphasis> n. sp. (Nematoda: Anguinidae) from western Iran

A new species in the genus Ditylenchus, D. stenurus n. sp. collected from western Iran, is described and illustrated herein based on morphological and molecular studies. The new species is characterised by a body length of 772 (663–863) μm, delicate stylet 6 (5–7) μm long, six lines in the lateral field. Median bulb of pharynx well-developed, muscular with crescentic valve. Post-vulval uterine sac well-developed, 35 (30–45) μm long, female tail elongate-conoid, becoming narrow suddenly with finely rounded terminus. The new species comes close in morphology and morphometrics to five known species of the genus, namely D. arachis, D. caudatus, D. clarus, D. myceliophagus, and D. nanus. DNA sequencing data was obtained on the partial 18S, D2/D3 expansion segments of the 28S rRNA gene and internal transcribed spacer (ITS). The phylogenetic relationships of this species with other Ditylenchus spp. using partial 18S–rDNA and D2/D3 indicated that D. stenurus n. sp. clustered together with several species belongs to the D. triformis-group i. e. D. africanus, D. destructor and D. halictus: all sharing a rounded tail terminus and six lines in lateral fields.     

“Red Ring” Disease in surinam

In Surinam no red ring disease in coconut, caused by the nematodeRhadinaphelenchus cocophilus, could be found under natural conditions. An inoculation experiment with the nematode in coconut palm and an experiment in oil palm where an entry for the vectorRhynchophorus palmarum was made, resulted in red ring symptoms. Collection of weevils of the speciesR. palmarum in coconut and oil palm plantations and in wild vegetation, showed that both vectors and nematodes occur in considerable numbers. The slow development of red ring in the inoculation experiment and of little leaf — another symptom, caused byR. cocophilus — in a period of excessive drought might give an explanation for the absence of red ring in Surinam. In the main coconut growing areas rainfall is poor as compared with other coconut-growing countries in the Caribbean.     

Stimulating<Emphasis Type="Italic">Orobanche ramosa</Emphasis> seed germination with an<Emphasis Type="Italic">Ascophyllum nodosum</Emphasis> extract

Algit Super®, an extract ofAscophyllum nodosum, was found to be an effective stimulant for the germination ofOrobanche ramosa seeds. The biological activity of Algit Super® was tested at a wide range of concentrations from 2.5 v/v to 1.2 × 10^?3 v/v. The seed germination in all studiedO. ramosa populations showed a concentration dependence, with an inhibitory effect at higher concentrations. The response ofO. ramosa to Algit Super® resembled its response to the reference stimulant GR24. VariousO. ramosa populations demonstrated differential response to the stimulant.     

New predators for biocontrol under glass

Several species ofOrius are under investigation in the UK, Europe and North America for the biological control of thrips, especially western flower thrips(Frankliniella occidentalis). The available species are briefly compared and findings on effectiveness and oviposition ofO. laevigatus are reported.     

Feeding preference of Thaumastocoris peregrinus on several Eucalyptus species and the relationship with the profile of terpenes in their essential oils

The feeding preference by Thaumastocoris peregrinus, Carpintero and Dellapé (Heteroptera: Thaumastocoridae) on different Eucalyptus species was evaluated through choice tests in a paired comparisons design. Twenty individuals per combination were tested over a 48 h period, and each one was offered leaves of two species at a time, in all possible combinations. Preference was determined by counting the number of insect excrements on each plant as a proxy for effective feeding, and then ranked through a paired comparison matrix. A linearity index was calculated to test for hierarchy preferences and, after that, a cardinal index (David’s score) was calculated to assign a preference value for each species. The essential oils were extracted from leaves of each Eucalyptus species, and their chemical composition determined through GC-MS. The results show a significant and strictly linear feeding preference ranking between the species tested. The order of preference between species was E. viminalis > E. grandis > E. tereticornis > E. dunnii > E. maidenii > E. globulus. The qualitative and quantitative chemical compositions of the essential oils of these Eucalyptus species differed. A significant correlation was found between the feeding preferences and the concentrations of 1,8-cineole as a repellent and p-cymene as a feeding stimulant. These results underline the importance of selecting the right Eucalyptus species in areas infested by T. peregrinus.     

Screening for Antifungal Potential of Plant Extracts of Fifteen Plant Species Against Four Pathogenic Fungi Species

The antifungal activity of fifteen wild plant species grown in the Al-Qassim region, Saudi Arabia, was investigated against the fungi species Fusarium solani, Botrytis cinerea, Alternaria alternata and Stemphylium botryosum at concentrations of 10, 20, 40 and 80?g/L. The inhibitory effect of test extracts varied among examined fungi, and Fusarium solani exhibited the least sensitivity compared to other fungi species. Antifungal activity of the tested extracts was proportional to the applied dose. Extracts of Lactuca virosa, Neurada procumbens, Ochradenus baccatus and Cyperus conglomerates showed relatively low inhibition effects on the fungi species. The most effective plants were Pulicaria undulata, Artemisia monosperma, Prosopis juliflora, Withania somnifera and Rumex vesicarius. At 80?g/L, extracts of these plant species reduced mycelial growth of Botrytis cinerea by 16.5–32.2%, of Fusarium solani by 11.1–27.9%, of Alternaria alternaae by 26.9–63.5% and of Stemphylium botryosum by 22–40%. The methanolic extract of the most effective plant species was further fractioned with hexane, methylene chloride and ethyl acetate. The obtained fractions varied in their effects on mycelial growth of the four tested fungi. Using the same fraction resulted in different inhibition effects on mycelial growth of all tested fungi. The antifungal activity of each crude extract tended to be distributed among its three fractions, probably because the bioactive components were also distributed among the fractions.     

Differential binding of a N-phenylformamidoxime compound in cell-free extracts of benzimidazole-resistant and-sensitive isolates of Venturia nashicola,Botrytis cinerea and Gibberella fujikuroi

Venturia nashicola isolates with a high level of resistance to carbendazim showed either increased sensitivity or were resistant to theN-phenylformamidoxime compoundN-(3,5-dichloro-4-propynyloyphenyl)-N′-methoxyformamidine (DCPF). Isolates with an intermediate or low level of carbendazim resistance were resistant to DCPF. Increased sensitivity to DCPF was also associated with a high level of carbendazim resistance inBotrytis cinerea but not with a moderate resistance level. Increased sensitivity to DCPF was not observed in carbendazim resistant isolates ofGibberella fujikuroi.Binding of [¹⁴C]DCPF in cell-free mycelial extracts of the highly carbendazim-resistant and DCPF-sensitive isolate ofV. nashicola was higher than in those of DCPF-resistant isolates that were either highly-resistant, intermediately resistant, or weakly resistant to carbendazim or were sensitive to carbendazim. [¹⁴C]carbendazim binding in extracts of highly carbendazim-resistant isolates ofB. cinerea was lower than that in extracts of sensitive isolates, whereas [¹⁴C]DCFP binding was higher. A decreased [¹⁴C]carbendazim binding was also observed in extracts of carbendazim-resistant isolates ofG. fujikuroi, binding of [¹⁴C]DCPF, however, was similar in extracts of both carbendazim-resistant and sensitive isolates.     

Effects of triazole fungicides on sterol biosynthesis during spore germination of Botrytis cinerea,Venturia inaequalis and Puccinia graminis f. sp. tritici

With three plant pathogens,Botrytis cinerea, Venturia inaequalis and Puccinia graminis f. sp.tritici, the time course of sterol biosynthesis during spore germination was examined by labeling experiments along with the question whether this pathway could be inhibited by triazole fungicides. Conidia ofB. cinerea andV. inaequalis are able to synthesize sterols immediately after the beginning of the germination process when the germ tubes have not yet emerged. On the contrary uredospores ofP. graminis start sterol biosynthesis after 6 to 8 h germination time almost at the end of the germ tube phase, indicating that sterol reserves of the spores are likely to be used for the germ tube growth.The sterol C-14 demethylation appeared to be the rate limiting step within the sterol biosynthetic pathway: the half life of 24-methylenedihydrolanosterol was less than 1 h forB. cinerea. It was more than 1 h forV. inaequalis and 3 h forP. graminis. Independent of these differences in the time course of sterol biosynthesis and in the C-14 demethylation rate, the synthesis of sterols in germinating spores was strongly inhibited by triazole fungicides in all three pathogens examined. In contrast toP. graminis, this inhibition could be demonstrated withB. cinerea andV. inaequalis even in ungerminated conidia, indicating that the fungicides were rapidly taken up and reached their target within 1 or 2 h. These results are discussed along with the question whether spore germination can be used as a bioassay for the estimation of sensitivities of triazole fungicides.