Meloidogyne enterolobii development and reproduction in tomato plants treated with resistance inducers

Summary Meloidogyne enterolobii is a species capable of overcoming plant resistance moderated by the Mi-1 gene, which is effective against most species of root-knot nematode. This study evaluated the effect of induced resistance in tomato plants (Solanum lycopersicum ‘H-9553’) with the Mi-1 gene against the development and reproduction of M. enterolobii. Seedlings of tomato ‘H-9553’ were transplanted into pots, inoculated with 2000 eggs and second-stage juveniles (J2) of M. enterolobii and treated with Acibenzolar-S-Methyl, Bacillus subtilis, B. subtilis + B. licheniformis + Trichoderma longibrachiatum and extract of Reynoutria sachalinensis. The plants were collected at 5, 10, 15, 20, 25 and 30 days after inoculation (DAI) for the analyses of nematode penetration and development, and at 30 DAI for nematode reproduction. The use of B. subtilis increased fresh root weight when compared to the other treatments (20 DAI). There was a reduction in penetration of J2 in the roots of plants subjected to different resistance inducers. The population density of M. enterolobii was significantly reduced only when plants were treated with R. sachalinensis, indicating it as a potential resistance-inducing agent in tomato plants.

Development of a new in vivo protocol through soil inoculation to investigate sugar beet resistance towards Ditylenchus dipsaci penetration

Summary The stem nematode, Ditylenchus dipsaci, causes severe damage in sugar beet. To date, nematode inoculation through the leaf axil has been used as the standard method to investigate D. dipsaci interaction with sugar beet under in vivo conditions. To get as close as possible to field conditions, we established a new screening mechanism to perform soil inoculation. The most suitable inoculation time point, inoculum level and positioning on sugar beet, as well as rearing process on carrots, were determined. At a 15:8°C day:night temperature regime, penetration rates of D. dipsaci were at maximum following soil inoculation at plant emergence. Up to 115 nematodes penetrated sugar beet seedlings 22 days post-planting with an inoculum level of 1000 nematodes into the soil at plant emergence. Ditylenchus dipsaci penetration rate was higher in plants with soil inoculation than with inoculation on to the leaf axil. High soil moisture increased nematode migration into seedlings when D. dipsaci inoculation was carried out in four holes 1 cm from the plant base. Rearing the nematodes for 35 days at 20°C on carrot discs resulted in an infective inoculum containing up to 50% eggs. We recommend a soil inoculation of 1000 freshly extracted nematodes per pot at plant emergence. The nematode suspension has to be previously reared for 35 days on carrot discs to obtain active D. dipsaci inoculum. This system will allow for the selection of suitable sugar beet genotypes that suppress nematode penetration, in support of breeding for resistance against D. dipsaci.

Morphological and Molecular Identification of Two Florida Populations of Foliar Nematodes (Aphelenchoides spp.) Isolated From Strawberry With the Description of Aphelenchoides pseudogoodeyi sp. n. (Nematoda: Aphelenchoididae) and Notes on Their Bionomics

Two Florida populations of foliar nematodes were collected from strawberries originating from Cashiers, North Carolina (USA) located west from Willard, the type locality of Aphelenchoides besseyi. Both nematodes were cultured on Monilinia fructicola and identified using morphological characteristics and molecular assays as Aphelenchoides besseyi and Aphelenchoides pseudogoodeyi sp. n., a herein described new species related to Aphelenchoides goodeyi belonging to the Group of Aphelenchoides exhibiting stellate tails. The morphological and biological characters of Florida A. besseyi fit those of the original description of this species. A. pseudogoodeyi sp. n., which was initially misidentified as Aphelenchoides fujianensis, differed from the type population of the latter species from China because it was without males, and females lacked a functional spermatheca, whereas type A. fujianensis is an amphimictic species. Phylogenetic analyses using near full-length 18S ribosomal RNA (rRNA), the D2-D3 expansion fragments of 28S rRNA, and partial COI gene sequences indicated that A. besseyi is a species complex. A. pseudogoodeyi sp. n. grouped in different clades from those of the type A. fujianensis, instead merging with populations identified of ‘A. fujianensis’ from Brazil and other countries, suggesting that the latter are conspecific and incorrectly identified. The Florida A. besseyi infected strawberry and gerbera daisy, but not soybean and alfalfa. A. pseudogoodeyi sp. n. is mainly mycetophagous. Localized inoculation of 300 specimens applied with filter paper adhering to the blade of the soybean leaves resulted in nematode penetration into the mesophyll with subsequent development of lesions limited to the inoculated area of the blade.

Life Cycle of Heterodera glycines in Resistant and Susceptible Soybean

The life cycle of the soybean cyst nematode lasts approximately 21-24 days at temperatures ranging from 23 °C to 25 °C. Mean temperatures above 25 °C are often found in Goiás State and in other Brazilian regions. Thus, the aim of the present study is to assess the penetration and cycle duration of Heterodera glycines Type 0- (race 3) in nematode-resistant and susceptible soybean cultivars grown in greenhouse under controlled conditions. The study was conducted at soil temperatures ranging from 23.9 °C to 31.1 °C using two soybean cultivars that were assessed in ten different periods; each assessment was conducted in six plants. The herein used soybean cultivars were BRS Valiosa RR and BRSGO 8860RR, which were, respectively, susceptible and resistant to the nematode. Root staining assessments were performed 2, 4, 6, 9, 12, 15, 18, 21, 24 and 30 days after inoculation (DAI). Besides the root staining assessments, the females and eggs were also assessed through extraction using the sieving and flotation method, at the 30th DAI. Heterodera glycines J2 penetration was similar in both the susceptible and the resistant cultivars throughout the assessment period. It indicates that the nematode penetration was not affected by resistance. The Heterodera glycines cycle at soil temperature ranging from 23.9 °C to 31.1 °C and at room temperature ranging from 27.0 °C to 36.3 °C was complete in 15 days, in both the susceptible and the resistant cultivars. A similar number of J2 has penetrated the roots of both cultivars and greater penetration intensity was found from the 6th to the 15th DAI. The peak J3, J4 and female formation period in the resistant cultivar was later than that observed in the susceptible cultivar.

Tagetes minuta Propagation and Interaction With Nematoide

Tagetes minuta is a plant presenting pest and disease control potential, although its activity on some plant parasite nematode species is poorly investigated. The aim of the current study is to evaluate the best T. minuta propagation way, as well as the plant reaction to nematodes such as Heterodera glycines, Meloidogyne incognita and Pratylenchus brachyurus, through nematode penetration and reproduction studies and root morphological assessments. Seedlings obtained from woody cuttings showed larger rooting and stem diameter. Heterodera glycines penetration was higher than that recorded for M. incognita. However, both species recorded reproduction factor (RF) lower than one, as well as maximum RF values 0.34 and 0.02 for H. glycines and M. incognita, respectively. The highest FR recorded for T. minuta were found in P. brachyurus (0.96 and 0.80) in the 60th and 80th day after inoculation (DAI). Root anatomy changes were observed in the 80th DAI in plants inoculated with P. brachyurus. Tagetes minuta was resistant to all nematodes; however, it did not prevent P. brachyurus activity in its roots.

Antagonistic Effects of Java against Plant Parasitic Nematodes

One of the main phytonematode control alternatives is the use of antagonistic plants in crop rotation or succession systems. Although java legume shows antagonist potential to control Meloidogyne javanica, its reaction to other nematodes was not investigated so far. Thus, the aim of the current study is to assess the penetration and reproduction factor (RF) of M. incognita, Rotylenchulus reniformis and Pratylenchus brachyurus in java, using soybean as control. Plants individually inoculated with 1000 specimens from each nematode were assessed 5, 10, 15, 20, 25 and 30 days after inoculation (DAI) for nematode penetration and development. The RF was assessed under two inoculum levels of each nematode (1000 and 700 specimens) 60 days after inoculation, for M. incognita and R. reniformis; and 80 days after inoculation, for P. brachyurus. Meloidogyne incognita and R. reniformis showed lower penetration and reproduction in java (RF < 1), whereas P. brachyurus showed higher penetration and RF > 1. Thus, the java legume can be considered resistant to M. incognita and R. reniformis, as well as susceptible to P. brachyurus.

Using Tannery Sludge to Manage Soybean Cyst Nematodes in Soybean Crops

Soybean crop (Glicyne max) is host to a range of pathogens, among them phytonematoids, with emphasis on the soybean cyst nematode (Heterodera glycines), which has recently caused great damages to the crop and compromised its productivity. Alternatives to the management of diseases, caused by phytonematoids, that are effective and less harmful to the environment, are increasingly being sought. Thus, the incorporation of organic compounds into the soil, such as tannery sludge (bovine chain by-product), presents great potential in the management of soil-borne pathogens, as well as reducing environmental impacts caused by the release into the environment. Thus, the aim of present study had as objective to evaluate the effect of different tannery sludge doses on the management of H. glycines in greenhouse. The study used a nematode-susceptible cultivar (BRS Valiosa RR) and followed a completely randomized experimental design, with 5 repetitions. The nematode penetration in the roots was assessed 10 days after inoculation (DAI), whereas the fresh root mass, the number of females per root gram, and the number of eggs per female were assessed 30 DAI. The tannery sludge is efficient in the management of H. glycines in nematode-susceptible soybean cultivars, reducing the number of females per gram of root, the number of juveniles of the second stage (J2) of the nematoid per root system and promoting increases in fresh mass of the roots. However, more studies are needed to understand the dynamics of the nematode reduction in the presence of the organic compound, since nematode reproduction was not affected by the presence of tannery sludge.

Fly ash effect on hatching, mortality and penetration of root-knot nematode (Meloidogyne incognita) in pumpkin roots

An experiment was conducted to observe the effect of fly ash on hatching, mortality and penetration of root-knot nematode (Meloidogyne incognita) in pumpkin roots. For hatching experiment different fly ash-extract concentrations (5, 10, 20, 30, 40, and 50%) were prepared. Hatching was significantly reduced in all concentrations, maximum being at 50% concentration. The mortality (%) of juveniles was observed in 1, 2, 3, 4, 5, 6 and 7th days with different levels (5, 10, 20, 30, 40 and 50 %) of fly ash-extract. All the levels were found harmful to juveniles. As the level was increased, the killing percentage of juveniles was also increased. Highest mortality was observed in 7th day with 50% level.For the penetration experiment, fly ash was mixed with soil to prepare different concentrations (5, 10, 20, 30, 40, and 50%). Seeds of pumpkin were grown in coffee cups filled with different mixtures. At two leaf stage, seedlings were inoculated with 2000 larvae. The penetrated larvae in roots were observed after 1, 2, 3, 4, 5, 6 and 7 days. Root penetration was found inversely proportional to concentration. Significant results in the suppression of nematode penetration were noted up to 40% concentration. However, none of the juveniles was penetrated at 50% concentration.International Journal of Environment Vol.5(3) 2016, pp.66-73

β-Aminobutyric Acid–Induced Resistance Against Root-Knot Nematodes in Rice Is Based on Increased Basal Defense

The nonprotein amino acid β-aminobutyric acid (BABA) is known to protect plants against various pathogens. The mode of action is relatively diverse and specific in different plant-pathogen systems. To extend the analysis of the mode of action of BABA to plant-parasitic nematodes in monocot plants, we evaluated the effect of BABA against the root-knot nematode (RKN) Meloidogyne graminicola in rice. BABA treatment of rice plants inhibited nematode penetration and resulted in delayed nematode and giant cell development. BABA-induced resistance (BABA-IR) was still functional in mutants or transgenics defective in salicylic acid biosynthesis and response or abscisic acid (ABA) response. Pharmacological inhibition of jasmonic acid (JA) and ethylene (ET) biosynthesis indicated that BABA-IR against rice RKN likely occurs independent of JA and ET. However, histochemical and biochemical quantification in combination with quantitative real-time reverse transcription-polymerase chain reaction data suggest that BABA protects rice against RKN through the activation of basal defense mechanisms of the plant, such as reactive oxygen species accumulation, lignin formation, and callose deposition.