Search Results (10)

Plant-parasitic nematodes are one of the economically most important pathogens, and how rising soil temperatures due to climate change impact their ability to damage crops is poorly understood. The current study was conducted to evaluate the reproduction biology (reproduction and virulence) of Rotylenchulus reniformis and Meloidogyne floridensis on tomato at soil temperatures of 26 °C (control), 32 °C, 34 °C, and 36 °C. The reproduction and virulence of both nematode species were differentially impacted by soil temperature. Relative to the control, the increase in reproduction of R. reniformis ranged from 20% to 116% while that of M. floridensis ranged from 22% to 133%. The greatest reproduction of R. reniformis was observed at 34 °C while that of M. floridensis was observed at 32 °C. Across all temperatures, reproduction of M. floridensis was 2.9 to 7.8 times greater than the reproduction of R. reniformis, suggesting that the former nematode species has a greater fecundity. The rates of change in reproduction relative to the controls were greater in M. floridensis than in R. reniformis, indicating that the latter nematode species is more resilient to changes in soil temperature. The virulence of both nematode species increased numerically or significantly at 32 °C and 36 °C, but not at 34 °C. The greatest virulence of both nematode species was observed at 36 °C at which 57% and 60% root biomass was lost to R. reniformis and M. floridensis, respectively, compared to the root biomass of uninoculated plants at that temperature. The results of the current study suggested that crop damage by nematodes will likely increase as global soil temperature continues to increase. Full article

Reniform nematode (Rotylenchulus reniformis) causes significant yield loss in cotton worldwide. In 2012, its detection in the Dawson-Callide region of Central Queensland prompted extensive surveys of cotton fields. The nematode was confirmed in 68% of sampled fields, with populations ranging from 2 to 3870 R. reniformis/200 mL of soil. Soil monitoring revealed increasing populations associated with consecutive cotton crops. However, when corn or sorghum replaced cotton, soil nematode populations significantly decreased. A two-year replicated field trial demonstrated that growing a non-host crop (such as biofumigant sorghum ‘Fumig8tor’, grain sorghum, or corn) significantly reduced nematode populations in the top 15 cm of soil compared to cotton. Unfortunately, when cotton was replanted the following season, nematode populations rebounded regardless of the previous crop. Only the ‘Fumig8tor’-cotton rotation resulted in significantly lower nematode populations than continuous cotton. Vertical soil sampling showed that rotating with a non-host crop significantly reduced nematode densities to a depth of 100 cm compared to cotton. However, when the field was replanted with cotton, nematode populations recovered, unaffected by cropping or soil depth. This study emphasises the importance of monitoring reniform nematodes in cotton soils for early detection and defining distribution patterns within a field, which may improve the effectiveness of management practices. These results suggest that one rotation out of cotton is not sufficient, as populations return to high levels when cotton is grown again. Therefore, two or more rotations out of cotton should be considered to manage this nematode. Full article

Reniform nematode (Rotylenchulus reniformis) is an important microparasite for Upland cotton (Gossypium hirsutum L.) production. Growing resistant cultivars is the most economical management method, but only a few G. barbadense genotypes and some diploid Gossypium species confer high levels of resistance. This study conducted a transcriptome analysis of resistant genotypes to identify genes involved in host plant defense. Seedlings of G. arboreum accessions PI 529728 (A2-100) and PI 615699 (A2-190), and G. barbadense genotypes PI 608139 (GB 713) and PI 163608 (TX 110), were inoculated with the reniform nematode population MSRR04 and root samples were collected on the fifth (D5) and ninth (D9) day after inoculation. Differentially expressed genes (DEGs) were identified by comparing root transcriptomes from inoculated plants with those from non-inoculated plants. Accessions A2-100 and A2-190 showed 52 and 29 DEGs on D5, respectively, with 14 DEGs in common, and 18 DEGs for A2-100 and 11 DEGs for A2-190 on chromosome 5. On D9, four DEGs were found in A2-100 and two DEGs in A2-190. For GB 713, 52 and 43 DEGs were found, and for TX 110, 29 and 117 DEGs were observed on D5 and D9, respectively. Six DEGs were common at the two sampling times for these genotypes. Some DEGs were identified as Meloidogyne-induced cotton (MIC) 3 and 4, resistance gene analogs, or receptor-like proteins. Other DEGs have potential roles in plant defense, such as peroxidases, programmed cell death, pathogenesis related proteins, and systemic acquired resistance. Further research on these DEGs will aid in understanding the mechanisms of resistance to explore new applications for the development of resistant cultivars. Full article

Around 300 different plant species are infected by the plant-parasitic reniform nematode (Rotylenchulus reniformis), including cotton. This is a devasting nematode with a preference for cotton; it is commonly found in Alabama farms and causes severe reduction in yields. Its first internal transcribed spacer (ITS1) region can be sequenced, and potential mutations can be found in order to study the population dynamics of the reniform nematode. The goal of our study was to sequence the ITS1 rDNA region in male and female RNs that were collected from BelleMina, Hamilton, and Lamons locations in Alabama. After separating the single male and female RNs from the samples collected from the three selected listed sites above, the ITS1 region was amplified selectively using specific primers, and the resulting products were cloned and sequenced. Two distinct bands were observed after DNA amplification of male and female nematodes at 550 bp and 730 bp, respectively. The analysis of sequenced fragments among the three populations showed variation in average nucleotide frequencies of female and male RNs. Singletons within the female and male Hamilton populations ranged from 7.8% to 10%, and the variable sites ranged from 13.4% to 26%. However, female and male BelleMina populations had singletons ranging from 7.1% to 19.7% and variable regions in the range of 13.9% to 49.3%. The female and male Lamons populations had singletons ranging from 2.5% to 8.7% and variable regions in the range of 2.9% to 14.2%. Phylogenetic (neighbor-joining) analysis for the two ITS1 fragments (ITS-550 and ITS-730) showed relatively high intra-nematode variability. Different clone sequences from an individual nematode often had greater similarity with other nematodes than with their own sequences. RNA fold analysis of the ITS1 sequences revealed varied stem and loop structures, suggesting both conserved and variable regions in the variants identified from female and male RNs, thus underscoring the presence of significant intra- and inter-nematodal variation among RN populations in Alabama. Full article

A greenhouse study was conducted to investigate the roles that host plant resistance and soil potassium (K) levels play in affecting Rotylenchulus reniformis Linford and Oliveira (Tylenchida: Hoplolaimidae) (RN) populations and early season cotton (Gossypium hirsutum L.) growth. Two upland, RN-resistant cotton lines (G. barbadense introgressions: 08SS110-NE06.OP and 08SS100), a genetic standard (Deltapine 16) and a commercially available susceptible cultivar (PHY 490 W3FE) were evaluated at four different levels of K [100% of recommended rate, 150% of recommended, 50% of recommended, and a base level] from seeding until harvesting, 60 days after sowing (DAS). Quadratic functions (r² = 0.82 to 0.95) best described the early season growth response of cotton genotypes to soil K. The base K level was associated with the lowest values for most morphological variables, including plant height (PH), mainstem nodes (MSN), leaf area, and dry weight at 30 DAS and 60 DAS. However, soil K did not affect RN population counts (RC). Additionally, soil K did not influence the rate of change in growth variables among genotypes. The resistant genotype 08SS110-NE06.OP showed greater growth in terms of time to first true leaf, PH, MSN, and above-ground dry weights compared to the commercially available susceptible genotype. No interaction between K and RN or genotype and RN was found in early season cotton growth. However, RC in pots of resistant genotypes was less than in pots of susceptible genotypes. Our research on the early season growth response to soil K by novel, RN-resistant genotypes and susceptible genotypes contributes to the development of improved RN resistance and fertilization management in cotton. Full article

Plant-parasitic nematodes (PPNs) are among the most notorious and underrated threats to food security and plant health worldwide, compromising crop yields and causing billions of dollars of losses annually. Chemical control strategies rely heavily on synthetic chemical nematicides to reduce PPN population densities, but their use is being progressively restricted due to environmental and human health concerns, so alternative control methods are urgently needed. Here, we review the potential of bacterial and fungal agents to suppress the most important PPNs, namely Aphelenchoides besseyi, Bursaphelenchus xylophilus, Ditylenchus dipsaci, Globodera spp., Heterodera spp., Meloidogyne spp., Nacobbus aberrans, Pratylenchus spp., Radopholus similis, Rotylenchulus reniformis, and Xiphinema index. Full article

There is little information about nematode pests associated with yam in China. Between 2020 and 2021, surveys of yam fields were conducted to investigate the abundance and prevalence of plant-parasitic nematodes in major yam growing areas. A total of 110 bulk soil samples from the yam rhizosphere and 48 yam tubers were collected from seven counties in Jiangxi and Shandong provinces. Standard protocols were used to extract nematodes from soil and tubers and identified at the genus level. In this study, 16 species and 13 nematode genera were recorded. The five most prominent species on the yam rhizosphere according to mean population densities were Pratylenchus coffeae (291/individuals), Meloidogyne (262/individuals), Rotylenchulus reniformis (225/individuals), Merlinius (224/individuals), and Helicotylenchus dihystera (171/individuals). In the tubers, the three most prominent species were Pratylenchus coffeae (415/individuals), Meloidogyne (331/individuals), and Rotylenchulus reniformis (115/individuals). These species were verified with appropriate molecular analysis. The high prevalence of the ectoparasite (Merlinius spp.) on the rhizosphere of yam also revealed that Merlinius spp. May be more important to yam than previously thought. Morphological and molecular analyses further confirmed the identity of the species as Merlinius brevidens and were characterized for the first time on yam in China. Minor morphometrical differences (slightly longer body and stylet) were observed in Chinese populations of M. brevidens compared to the original description. Additionally, this study reveals that M. brevidens isolated from China showed a higher nucleotide sequence in the ITS region compared to M. brevidens populations from India. This finding provides baseline information on the nematode pest occurrence on yam in China and calls for effective management. Full article

The reniform nematode, Rotylenchulus reniformis (Linford and Oliveira), remains a common, widespread nematode pest of cotton across the southern United States. Trials were conducted during 2017 at three non-irrigated locations: one location in Hamilton, MS, and two locations in Tchula, MS, in field settings with a history of cotton production and documented economically-damaging reniform nematode populations. Trials were designed to evaluate the response of two cotton cultivars to in-furrow nematicides consisting of aldicarb, 1,3-dichloropropene, and a non-treated control applied for nematode suppression. No significant interactions between cotton cultivar and nematicide were observed. However, treatment with 1,3-dichloropropene produced greater plant biomass, and plant height compared to aldicarb-treated cotton and the nontreated. Nematode densities were suppressed with the use of 1,3-dichloropropene compared to aldicarb and the non-treated control. The use of 1,3-dichloropropene resulted in positive early-season plant growth responses; however, these responses did not translate into greater yield. Full article

Sorghum/sorghum–sudangrass hybrids (SSgH) have been used as a cover crop to improve soil health by adding soil organic matter, enhancing microbial activities, and suppressing soil-borne pathogens in various cropping systems. A series of SSgH were screened for (1) allelopathic suppression and (2) improvement of soil edaphic factors and soil microbial profile against plant-parasitic nematode (PPNs). The allelopathic potential of SSgH against PPNs is hypothesized to vary by variety and age. In two greenhouse bioassays, ‘NX-D-61′ sorghum and the ‘Latte’ SSgH amendment provided the most suppressive allelopathic effect against the female formation of Meloidogyne incognita on mustard green seedlings when using 1-, 2-, or 3-month-old SSgH tissue, though most varieties showed a decrease in allelopathic effect as SSgH mature. A field trial was conducted where seven SSgH varieties were grown for 2.5 months and terminated using a flail mower, and eggplant was planted in a no-till system. Multivariate analysis of measured parameters revealed that increase in soil moisture, microbial biomass, respiration rate, nematode enrichment index, and sorghum biomass were negatively related to the initial abundance of PPNs and the root-gall index at 5 months after planting eggplant in a no-till system. These results suggested that improvement of soil health by SSgH could lead to suppression of PPN infection. Full article

There are numerous early-season pests of cotton, Gossypium hirsutum L., that are economically important, including tobacco thrips, Frankliniella fusca (Hinds), and reniform nematode, Rotylenchulus reniformis (Linford & Oliveira). Both of these species have the potential to reduce plant growth and delay crop maturity, ultimately resulting in reduced yields. A field study was conducted during 2015 and 2016 to evaluate the influence of tillage, at-planting insecticide treatment, and nematicide treatment on pest management, cotton development, and yield. Treatment factors consisted of two levels of tillage (no-tillage and conventional tillage); seven levels of at-planting insecticide treatments (imidacloprid, imidacloprid plus thiodicarb, thiamethoxam, thiamethoxam plus abamectin, acephate plus terbufos, aldicarb, and an untreated control); and two levels of nematicide (no nematicide and 1,3-dichloropropene). There were no significant interactions between tillage, at-planting insecticide treatment, or nematicide for any parameters nor was there a difference in the main effect of nematicide on thrips control or damage. The main effects of tillage and at-planting insecticide treatment impacted thrips densities and damage. The no-tillage treatments and aldicarb in-furrow or acephate seed treatment plus terbufos in-furrow significantly reduced thrips populations. Early-season plant response was impacted by tillage and at-planting insecticide treatment; however, that did not result in significant yield differences. In regard to nematicide treatment, the use of 1,3-dichloropropene resulted in lower yields than the untreated. Full article