Reproduction Factor Values Research Articles

Chemical composition and antioxidant properties of beetroot parasitized by Meloidogyne javanica and treated with elicitors

Beetroot is rich in nutrients and bioactive compounds, such as, betalains and phenolics. The objective of this work was to analyze the chemical composition and antioxidant properties of beetroot parasitized by Meloidogyne javanica and treated with elicitors. Beet seedlings were inoculated with 1000 eggs and second-stage juveniles of M. javanica and treated with elicitors based on mannan oligosaccharides, citrus biomass, or acibenzolar-S-methyl (ASM). At 60 days after inoculation, plants were evaluated for nematode reproduction factor (RF), proximate composition, betalains, phenolic compounds, and antioxidant activity. Beetroot was found to be susceptible to M. javanica, with RF values ranging from 15.26 to 27.94. ASM and citrus biomass treatments increased ash content by 15–25% in nematode-inoculated plants. There was no treatment effect on moisture or protein content, but uninoculated plants had higher total phenolic content (~35%) than inoculated plants. Nematode infection was found to compromise betalain production but did not impact antioxidant activity. Nematode-inoculated plants showed reduced sucrose content and increased glucose and fructose levels in all treatments. Regardless of the elicitor used, beetroots inoculated M. javanica exhibit deformities that render them unmarketable in fresh form. However, the results indicate that nematode-infected beetroot may be suitable for industrial processing and compound extraction.

Response of different crops and weeds to three biotypes of Meloidogyne graminicola: crop rotation and succession strategies for irrigated rice fields

Summary Rice, one of the most consumed cereal crops worldwide, is commonly grown under flooded conditions, which directly influences the nematode community. Meloidogyne graminicola is the predominant species in rice fields, causing significant damage and requiring integrated management practices. This study aimed to investigate the response of different Poaceae crops, soybean, and common weeds of rice to three biotypes of M. graminicola (G1, G2 and G3) recently detected in Brazil. The highest reproduction factor (RF) for the three nematode populations was detected in the weeds Echinochloa colonum and E. crus-galli, followed by rice and Italian ryegrass. Wheat ‘TBio Sonic’ and millet ‘ADR 500’ served as poor hosts to the nematodes, whereas black oat, white oat, signalgrass, millet ‘ADR 905’, maize, wheat ‘TBio Toruk’, and soybean acted as non-hosts (RF < 1) in both experiments. Of the three M. graminicola biotypes, G1 was the most aggressive, followed by G3 and G2 (lowest RF values). The findings of the current study can support the selection of crop rotation or succession approaches for the management of different biotypes of M. graminicola in irrigated rice fields.

Biological control of Pratylenchus brachyurus with isolates of Trichoderma spp. on soybean

Pratylenchus brachyurus is an important species of nematode as it causes significant yield losses in soybean crops in Brazil. The efficacy of Trichoderma asperellum T00 and Trichoderma harzianum ALL 42 were evaluated as biocontrol agents against P. brachyurus. The experiments were conducted under greenhouse conditions using the BRSGO Caiapônia and BRS 8560RR cultivars of soybeans. The application of these two fungal species significantly reduced the population density (PD) and reproductive factor (RF) of P. brachyurus in the cultivar BRSGO Caiapônia. In contrast, the PD and RF values for P. brachyurus in the cultivar BRS 8560RR remained stable after treatment with both species. The treatment of P. brachyurus (J2) with non-volatile metabolites from T. asperellum T00 and T. harzianum ALL42 resulted in mortality rates of 41% and 65%, respectively. The exposure to T. asperellum T00 and T. harzianum ALL42 did not alter the height, the size of the roots (RL), or the fresh mass of the aerial part (FSM) of BRSGO Caiapônia. On the other hand, the treatment of BRS 8560RR resulted in an increase in plant height, with no differences in RL and FSM. The activity of defense-related enzymes was determined in leaves of the two cultivars. In general, it was observed that the enzymes β-1,3-glucanase, chitinase and peroxidase showed higher activities in cultivar BRS 8560RR, while phenylalanine ammonia-lyase activity was higher in BRSGO Caiapônia. This study demonstrated that these two isolates of Trichoderma have potential for use in biological control of P. brachyurus in soybeans.

Assessment of the most suitable nematode inoculum density and plant growth period to screen coffee genotypes for their reaction to Meloidogyne incognita

Summary One of the concerns for nematological research is the absence of information on standard nematode population densities to be used when screening to assess resistance/susceptibility levels of a genotype. In addition, the length of the growth period, especially for perennial crops such as coffee, must also be known. The objective of this work was to evaluate the ideal evaluation periods and population densities of the root-knot nematode, Meloidogyne incognita, for phenotyping Coffea arabica genotypes. Seedlings of coffee ‘Mundo Novo’ with five leaf pairs cropped in 700 cm3 plastic pots were inoculated with population densities of 700, 1400, 2800, 5600 and 11 200 eggs of M. incognita per plant and evaluated at 90, 120, 150 and 180 days after inoculation (DAI) to determine the nematode reproduction factor (RF). The use of population densities of M. incognita from 700-2000 nematodes with evaluations between 90 and 180 DAI was the most suitable to obtain higher RF values and allows earlier and more accurate evaluations, which reduces the time for phenotyping in genetic screening programmes.

Resistance of new Coffea canephora clones to root-knot nematode (Meloidogyne incognita) in the western amazon

Root-knot disease is among the main diseases affecting coffee crop. The plant selection to the development new resistant cultivars is among one the most efficient methods of control. The present work aimed to quantify the resistance responses of Coffea canephora clones to root-knot nematode Meloidogyne incognita in the Western Amazon. For this, 17 previously selected clones were evaluated in three experimental trials, carried out in the municipalities of Ji-Parana and Porto Velho, Rondonia. The resistance to root-knot nematodes M. incognita were evaluated by the numbers of gall in the roots (NG) and by the reproductive factor (RF). The resistance response was also interpreted according the genetic diversity of the clones based in their morphological traits. The clones BRS3210, C12, BRS2314, BRS3137 and BRS1216 are resistant to M. incognita with RF of 0.34, 0.62, 0.79, 0.86 and 0.98, respectively. BRS3213, C125, C15, BRS2336, BRS3220 and C09 clones were classified as susceptible, with RF of 1.93, 1.95, 2.00, 2.31, 2.32 and 2.35. The BRS3193, C160and BRS2357 clones were classified as very susceptible, with RF values of 3.03, 4.41 and 5.82, respectively. The clustering based on the genetic diversity of morphological traits indicated that genotypes more similar to the Robusta botanic variety had lower RF. The hybrid plants showed intermediate degrees of resistance indicating the segregation for the character of the M. incognita resistance. The clones BRS3210, C12, BRS2299, BRS2314, BRS3137 and BRS1216expressed resistance responses to M. incognita with potential for growing resistant genotypes in the Western Amazon. Key words: Coffee; root-knot disease; plant breeding; Amazonian.

Reproduction Ability and Growth Effect of Pin Nematode, Paratylenchus nanus, With Selected Field Pea Cultivars.

Greenhouse experiments were conducted to determine the reproductive ability and effect of the pin nematode Paratylenchus nanus from North Dakota on field pea cultivars. Reproduction of P. nanus was determined on seven field pea cultivars using naturally infested field soils at low (1,500/kg of soil) and high (4,500/kg soil) initial pin nematode densities. Nematode effect on plant growth and seed yield was evaluated at 4,500 P. nanus per 1 kg of soil by artificially inoculating P. nanus on six field pea cultivars. Reproductive factor (RF) of P. nanus was observed to be greater at the low density than the high density of the nematode. At the low population density, RF values ranged from 1.10 to 11.20, whereas at the high density, RF ranged from 1.20 to 2.50. In experiments evaluating P. nanus effects on cultivar growth, the nematode (4,500 P. nanus per 1 kg soil) caused reduction (P < 0.05) of plant height in most cultivars tested, and it also significantly impacted dry shoot weight and dry seed weight in some experiments. Plant height and shoot weight reductions were the highest in the cultivar Arcadia (up to 37 and 53%, respectively), with a dry seed weight reduction up to 32%. This research demonstrated for the first time the negative impact of P. nanus on field peas in controlled greenhouse conditions, which is an important step toward developing effective management strategies to improve the productivity of this leguminous crop.

Impact of Globodera ellingtonae on yield of potato (Solanum tuberosum).

Globodera ellingtonae was described from Oregon and Idaho in 2012. Due to the close phylogenetic relationship of this nematode to the potato cyst nematodes G. pallida and G. rostochiensis, and evidence that G. ellingtonae reproduces on potato (Solanum tuberosum), potential damaging effects to potato by this nematode are of great concern. To evaluate the pathogenic effects of G. ellingtonae on potato, five field and two microplot trials were conducted over a four-year period including comparisons of a range of G. ellingtonae initial population densities (Pi) and potato cultivars. In two field trials, potato ‘Russet Burbank’ was inoculated with Pi of G. ellingtonae ranging from 0 to 80 eggs/g soil; a similar trial was conducted with potato ‘Désirée.’ In another field trial, potato cultivars varying in maturity lengths were either inoculated (80 eggs/g soil) or not with G. ellingtonae. In a final field trial, ‘Ranger Russet’ was inoculated with Pi of G. ellingtonae ranging from 0 to 360 eggs/g soil. Additionally, Russet Burbank was inoculated with G. ellingtonae Pi ranging from 0 to 169 eggs/g soil in microplots. In all trials, data on tuber yield, aboveground biomass, final eggs/cyst, final population densities (Pf), and reproduction factor (RF = Pf/Pi) were collected. In only two of six trials conducted with increasing levels of Pi, was there a significant negative correlation between Pi of G. ellingtonae and yield of potato. Based on the linear regression model of tuber yield on logPi for Russet Burbank, 30.5 to 40.9% yield loss was predicted at a Pi of 40 and 80 eggs/g soil, respectively, and for Ranger Russet, 16.5 and 19.7% yield loss was predicted at a Pi of 40 and 80 eggs/g soil, respectively. None of the potato cultivars inoculated with 80 G. ellingtonae eggs/g soil had significantly reduced yields compared to non-inoculated plants. Reproduction factor values across trials ranged from 4.0 to 8.3 when inoculated with Pi of 40 eggs/g soil, demonstrating that the nematode successfully invaded and reproduced on potato in all trials. Care should be taken in extrapolating the results from these experiments conducted in Oregon to probable effects of G. ellingtonae on potato in other environments.KeywordsPotato, Damage, Globodera, Regression

Meloidogyne luci, a new root‐knot nematode parasitizing potato in Portugal

In 2013, during a field survey conducted in Portugal on potato, Solanum tuberosum, an unusual esterase (EST) phenotype was detected in a root‐knot nematode (RKN) from potato roots collected in Coimbra. This Portuguese isolate was purified and maintained on tomato, S. lycopersicum, and morphological, biochemical and molecular characteristics were studied. Perineal pattern morphology was highly variable, similar to Meloidogyne ethiopica and not useful for identification. The EST phenotype, from young egg‐laying females, displayed three bands similar to the Brazilian M. luci (L3) and distinct from M. ethiopica (E3). Phylogenetic analyses of mitochondrial cytochrome oxidase subunit I and the mitochondrial DNA region between COII and 16S rRNA genes revealed that the Portuguese isolate grouped with M. luci isolates close to M. ethiopica isolates. However, considering the ITS1‐5.8S‐ITS2 region, the Portuguese isolate grouped with isolates of M. luci, M. ethiopica and M. hispanica, which limits the confidence of this region for M. luci diagnosis, and its differentiation from other species with morphological similarities. The M. luci pathogenicity to potato was also assessed in 16 commercial cultivars and compared with M. chitwoodi, considered to be a quarantine RKN species by EPPO. All potato cultivars were susceptible to both Meloidogyne species with gall indices of 5 and higher reproduction factor values ranging from 12.5 to 122.3, which suggests that M. luci may constitute a potential threat to potato production. In the present study, M. luci is reported for the first time attacking potato in Portugal.

Wild Coffea arabica resistant to Meloidogyne paranaensis and genetic parameters for resistance

Arabica coffee production is based on highly productive cultivars; however, these cultivars are susceptible to infestation by several biotic agents, including root-knot nematodes. Collections of wild Coffea arabica germplasm represent an important source of genetic variability for resistant cultivar development. In this study, 1046 plants derived from 71 wild coffee trees were evaluated with respect to Meloidogyne paranaensis resistance. In addition to information on plants reactions, we also evaluated the genetic parameters related to resistance. Progenies from the five most promising plants were also evaluated regarding resistance to M. incognita and M. exigua. The yield potential of selected plants was estimated through analysis of data for fruits harvested in 4 different years. Forty-seven plants were considered resistant based on reproduction factor values. The estimated heritability was high for all analyzed variables leading to substantial selection gain, mainly at the progeny mean level. On the basis of heritabilities and genetic correlations, we conclude that selection could be performed based on values of the gall and egg mass index. However, higher genetic gain could be obtained based on nematode count variables. A second experiment confirmed the reactions of the selected five plants to M. paranaensis, and multiple resistance was detected in three of them. The resistant accessions also have yield potential.

Degree of nematode resistance to Meloidogyne incognita race 2 in Artemisia afra ethnomedicinal plant

Attempts are underway to cultivate Artemisia afra as an alternative crop due to its medicinal properties which span all 10 international medicinal systems. However, most crop-related developmental projects had not been successful due to the widespread distribution of root-knot (Meloidogyne species) nematodes, which had a wide host range. The objective of this study was to determine the host-status and host-sensitivity of A. afra to M. incognita race 2 was determined at six levels of inoculation in a pot trial. At 56 days after inoculation, treatments were highly significant on reproductive factor (RF) and root galls, contributing 87 and 89% in total treatment variation of the respective variables. At lower inoculation (Pi≥75 eggs and second-stage juveniles), RF values were above unity, whereas at moderate (Pi 250–500) and high (Pi≥1125) inoculation levels, RF values were less than unity. Gall rating at all inoculation levels ranged from 1 to 2 on the North Carolina Differential Scale, whereas M. incognita race 2 infection had no significant effects on growth of A. afra. In conclusion, A. afra had attributes of plant tolerance to infection by population of M. incognita race 2.

Weeds Hosts of Nematodes in Sugarcane Culture

ABSTRACT The presence of weeds and nematodes can affect of sugarcane yield. This research evaluated whether weeds that are very frequent in mechanized harvested sugarcane can be hosts for root-knot nematodes: Meloidogyne incognita or Meloidogyne javanica. Regarding nematode hospitability, ten weed species as well as a control sample (tomato) were evaluated; they were inoculated with M. incognita and M. javanica. The plants were inoculated with 2,000 eggs and second-stage juveniles (J2), and there were three plants per experimental unit (6,000 eggs and J2 per pot - repeatition); 60 days after inoculation (DAI), the plants were removed and evaluated according to reproduction factor (RF), nematode final population (FP) and reproducibility index (RI). Regarding weed hospitability, it was found that Luffa aegyptiaca acted as a host for both nematodes, with RF &gt; 1, which was higher than the control sample. Digitaria horizontalis was classified as a host for M. incognita and as a non-host for M. javanica. Mucuna aterrima and Crotalaria spectabilis presented the lowest RF and FP. Ricinus communis and Ipomoea triloba presented galls when inoculated with M. incognita, but were not considered host, since they presented RF &lt; 1. None of the weed species was considered immune, i.e., with RF = 0. The lowest RF values of M. incognita (race 3) were related to Crotalaria spectabilis and Euphorbia heterophylla plants. This demonstrates the ability of crotalarias in decreasing nematode population in the field and justifies its use in several areas before planting main crops.

Interrelations between commercial beetroot (Beta vulgaris) cultivars and Meloidogyne species

ABSTRACTMost beetroot (Beta vulgaris) cultivars in South Africa are exotic and were specifically bred for root-knot (Meloidogyne species) nematode populations in their countries of origin. Due to the widespread distribution of different Meloidogyne species and races, exotic cultivars should be matched with nematode populations in importing countries. The objective of this study was to determine the interrelations between exotic beetroot cultivars ‘Detroit Red Dark’ and ‘Crimson Globe’ with Meloidogyne species in the predominant beetroot-producing regions in South Africa. Different inoculum series of M. incognita and M. javanica were used on the two beetroot cultivars. At 56 days after initiating the treatments, roots of both cultivars had small undeveloped root galls, with the reproductive factor values of M. incognita on ‘Detroit Dark Red’ being above and below unity at low (≤125 inoculation) and high (≥250 inoculation) nematode levels, respectively. Growth of ‘Detroit Dark Red’ was significantly stimulated and inhibited at low and high nematode infection levels, respectively. In contrast, RF values for M. javanica on ‘Crimson Globe’ were below unity, without any significant effects on plant growth. In conclusion, ‘Detroit Dark Red’ was tolerant to M. incognita, whereas ‘Crimson Globe’ was resistant to M. javanica.

Penetration and Reproduction of Meloidogyne javanica on Leguminous Crops

AbstractThe use of antagonist plants is one of the most effective methods in the management of root–knot nematodes, and several plants recommended for this purpose are nitrogen‐fixing plants that act as green manure because of the amount of mass produced. The mode of action of some species has already been investigated, but this has yet to be elucidated for many plants researched as antagonists. Thus, this study aimed to assess the penetration and reproduction of Meloidogyne javanica on the root system of three species of crotalaria, as well as Mucuna deeringiana, Cajanus cajan, Canavalia ensiformis, Macrotyloma axillare and Stylosanthes capitata, with soya bean used as control treatment. Thus, plants inoculated with the nematode were assessed 5, 10, 15 and 20 days after inoculation (DAI), for nematode penetration and development. After 60 days of inoculation, the nematode reproduction factor (RF) was assessed. The plants did not prevent M. javanica penetration, which differed at varying degrees, according to the time of assessment and the plant species investigated. However, the nematode reproduction was impaired in all the leguminous crops assessed, with (RF)&lt;1 in all the plants, while in soya bean the RF values were 2.85 and 2.56, in the respective experiments.

Phenotypic variability and response of Brazilian oat genotypes to different species of root-knot and root-lesion nematodes

In Brazil, oat (Avena sativa) is widely cultivated as a winter crop mainly in the south region. However, there are several species of nematodes that are of economic importance to oats and knowledge about the reaction of cultivars to root-knot and root-lesion nematodes is sparse. Thereby, in this present work we aimed to characterize the host response of some selected oat genotypes to Meloidogyne incognita (Mi) race 3, M. javanica (Mj), M. paranaensis (Mp), M. enterolobii (Me), and P. brachyurus (Pb) under greenhouse conditions, based on the nematode reproductive factor (RF) and number of nematodes per gram of roots [nem (g root)−1]. We also determined the variance components associated with root-knot and root-lesion resistance. Results revealed variation in the susceptibility of cultivars to nematodes tested, except for M. enterolobii, in which all cultivars tested were highly resistant. The cultivar IPR Afrodite was the most resistant to root knot species (Mi race 3, Mj, Mp and Me), whereas all cultivars tested were considered susceptible to Pb. Data of nem (g root)−1 confirmed the characterization of the cultivars based on RF values.

English

Bio-pesticides, when used as a post-planting pesticide, are limited by their potential ability to suppress the pest and their degree of phytotoxicity. Baseline information on the suitability of fermented crude extracts (FCE) of Cucumis africanus fruit as a post-planting bio-nematicide was determined on Meloidogyne incognita and growth of tomato in pot trials. Seedlings were inoculated with 1,130 eggs and juveniles/pot, while FCE were applied weekly at 0, 10, 20, 30, 40, 50 and 60% dilutions. At harvest, nematode and plant data were subjected to analysis of variance and the curve-fitting allelochemical response data (CARD) computer-based model, respectively. Relative to inoculation level, final nematode population density (Pf) at the same level of inoculation was reduced, while increasing dosages had no effect on Pf and reproductive factor values. Since increasing dosages had no effect on Pf, the material could possibly still reduce this variable when applied below 10% dilutions. Dosages used were phytotoxic to tomato plants, but CARD model demonstrated that the material stimulated plant growth at dosages below 10%. In conclusion, baseline information from CARD model suggested that FCE from C. africanus fruit have the potential to serve as a bio-nematicide and bio-fertiliser on tomato provided the material was applied below 10% dilutions. Key words : Cucumis africanus , bionemagation, effective microbe organisms, ground leaching technology, root-knot nematode.

Host-status and host-sensitivity of wild Cucumis species to Meloidogyne incognita race 4

Wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myriocarpus), which are highly resistant to the southern root-knot nematode (Meloidogyne incognita) race 2, have the potential for serving as seedling rootstocks for the highly nematode-susceptible watermelon (Citrullus lanatus) cultivars. In South Africa, due to high labour costs, most cotton farmers are turning to watermelon production. In these regions, there is high incidence of M. incognita race 4. A pot experiment in the greenhouse was, therefore, initiated to investigate the host-status and host-sensitivity of Cucumis africanus and Cucumis myriocarpus to M. incognita race 4, when inoculated with 0, 200, 600, 100, 1400, 1800 and 2200 eggs and second-stage juveniles (J2s). At harvest, 56 days after inoculation, the reproductive factor values at all levels of inoculation were less than one. Penetration indices on both plant species were greater than one, suggesting that the resistance was post-infectional and therefore, introgressible. Sex (male: female) ratios of M. incognita race 4 on the two Cucumis species were greater than one, suggesting that more J2s were converted into males. Infection of Cucumis species by the test nematode had no effect on yield components of the two plant species due to poor feeding sites. The two Cucumis species were, therefore, resistant to M. incognita race 4, with post-infectional resistance, where the sex ratio was skewed towards maleness. Thus, the two Cucumis species have the potential to be used as nematode-resistant rootstocks in watermelon production.

Reprodução de Meloidogyne spp. em porta-enxertos e híbridos de pepino

A enxertia é uma técnica alternativa frequentemente recomendada para a cultura do pepino em áreas infestadas com nematóides das galhas. O presente trabalho teve como objetivo determinar o fator de reprodução de Meloidogyne javanica e de Meloidogyne incognita raça 2 em seis porta-enxertos para pepino (abóbora 'Menina Brasileira', moranga 'Exposição', 'Shelper', 'Tetsukabuto', 'B8-A Tetsukabuto' e 'Excite Ikki') e quatro híbridos de pepino (Cucumis sativus) tipo japonês ('Yoshinari', 'Kouki', 'Taisho' e 'Tsuyataro'). Foram conduzidos dois experimentos em casa-de-vegetação, um com cada espécie do nematóide, sendo cada parcela constituída de uma planta mantida em vaso contendo 2 litros de solo autoclavado. Nove dias após transplante, cada planta foi inoculada com 5.000 ovos e juvenis de segundo estádio (população inicial - Pi) de M. javanica ou M. incognita raça 2. Tomateiros 'Rutgers' foram utilizados como padrão de viabilidade do inóculo, em ambos os experimentos. O delineamento experimental foi inteiramente casualizado com cinco repetições por tratamento. Sessenta dias após a inoculação, cada planta foi avaliada, quanto ao peso fresco da raiz, número total de nematóides presentes no solo e na raiz (população final - Pf), número de nematóides/g de raiz e fator de reprodução de ambas as espécies de Meloidogyne (FR=Pf/Pi). Todos os porta-enxertos e híbridos de pepino testados apresentaram fatores de reprodução superiores a um, proporcionando a multiplicação de M. javanica e de M. incognita raça 2, porém, os valores nos híbridos de pepino foram superiores aos dos porta-enxertos.

Pathogenicity and reproductive fitness of Pratylenchus brachyurus on cowpea

AbstractThe lesion nematode Pratylenchus brachyurus is widespread in cowpea plantations throughout the tropics and sub-tropics. However, the pathogenicity of P. brachyurus on cowpea has been scarcely studied. In this work, it was demonstrated in two glasshouse experiments that an isolate (Pb20) of P. brachyurus was pathogenic to cowpea cv. IPA-206, adversely affecting the plant growth and pod formation and filling. Initial population levels of 5000 and 15 000 nematodes per plant caused reduction of root growth and typical decay of root tissue. The third experiment demonstrated that all six cowpea cultivars selected for evaluation supported reproduction of three isolates of P. brachyurus (Pb20, Pb21 and Pb23) in their roots, although the reproduction factor values obtained indicated that they were dissimilar in their reproductive fitness. Low resistance to P. brachyurus was reported for at least one tested cultivar, but apparently of an insufficient degree to be effective for field management of the nematode.