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Rotylenchulus reniformis Linford and Oliveira (reniform nematode) infestation has been a concerning issue in the Cotton Belt region of the United States for the past decade. Reniform nematode damage is more evident on cotton compared to other row crops in US Mid‐South because they share common edaphic conditions to sustain and develop. Annual cotton (Gossypium spp.) yield loss over the United States due to reniform nematode ranged from 1.14% to 2.37% in the past decade but exceeded 8% in the US Mid‐South States such as Mississippi. Yield losses due to nematode damage are mainly due to inconsistent control by cultural and chemical practices. In addition, there are location‐specific responses due to agronomic practices that result in its wide adaption. This review summarizes factors that influence reniform nematode infestations and the process of a plant infection, as well as management practices to mitigate nematode cotton production losses in the United States. The recent development of resistant cotton germplasm is a promising tool for reniform nematode management, although limited research has been conducted on the physiological mechanisms of resistance. In addition, understanding the role of host plant resistance and the interaction with other soilborne pathogens or abiotic stresses to control the nematode also is lacking. Future research must investigate best suited production practices specific to a region that could exploit the full potential of host plant resistance to minimize the risk of reniform nematode damage in cotton while protecting the environment. Core Ideas Reniform nematode caused up to 8% annual loss to cotton production in the US Mid‐South over the last decade. Chemical and cultural practices showed inconsistent control of reniform nematode damage. The recently released reniform nematode‐resistant varieties are invaluable for cotton producers, industry, and researchers.

Plant-parasitic nematodes (PPNs) interact with plants in different ways, for example, through subtle feeding behavior, migrating destructively through infected tissues, or acting as virus-vectors for nepoviruses. They are all obligate biotrophic parasites as they derive their nutrients from living cells which they modify using pharyngeal gland secretions prior to food ingestion. Some of them can also shield themselves against plant defenses to sustain a relatively long lasting interaction while feeding. This paper is centered on cell types or organs that are newly induced in plants during PPN parasitism, including recent approaches to their study based on molecular biology combined with cell biology-histopathology. This issue has already been reviewed extensively for major PPNs (i.e., root-knot or cyst nematodes), but not for other genera (viz. spp.). PPNs have evolved with plants and this co-evolution process has allowed the induction of new types of plant cells necessary for their parasitism. There are four basic types of feeding cells: (i) non-hypertrophied nurse cells; (ii) single giant cells; (iii) syncytia; and (iv) coenocytes. Variations in the structure of these cells within each group are also present between some genera depending on the nematode species viz. or . This variability of feeding sites may be related in some way to PPN life style (migratory ectoparasites, sedentary ectoparasites, migratory ecto-endoparasites, migratory endoparasites, or sedentary endoparasites). Apart from their co-evolution with plants, the response of plant cells and roots are closely related to feeding behavior, the anatomy of the nematode (mainly stylet size, which could reach different types of cells in the plant), and the secretory fluids produced in the pharyngeal glands. These secretory fluids are injected through the stylet into perforated cells where they modify plant cytoplasm prior to food removal. Some species do not produce specialized feeding sites (viz. ), but may develop a specialized modification of the root system (e.g., unspecialized root galls or a profusion of roots). This review introduces new data on cell types and plant organs stimulated by PPNs using sources varying from traditional histopathology to new holistic methodologies.

Cotton (Gossypium hirsutum L.) genotypes resistant to reniform nematode (RN) (Rotylenchulus reniformis Linford and Oliveira) have been recently developed to reduce yield losses from RN, yet little is known of their agronomic responses under field conditions. This research was conducted to determine if RN population vary cotton growth and development and yield among RN resistant (G. barbadense introgressions; 08SS110‐NE06.OP and 08SS100) and susceptible cotton genotypes (Deltapine 16 and PHY 490 W3FE) in environments infested with RN. The study was conducted over 2 yr (2017 and 2018) in field plots naturally infested with RN population. Growth analysis was conducted at 1‐ or 2‐wk intervals starting from 4 wk after planting (WAP) to 12 WAP. Soil samples were taken from the top 40‐cm soil depth before planting and after harvesting to determine RN populations. The three‐parameter sigmoidal functions best described (r2 = .95–.99) growth of cotton genotypes along the season, but no differences were observed for maximum growth rates among genotypes. Post‐harvest RN populations significantly increased in plots grown with susceptible cotton genotypes, while RN reproduction was inhibited resulting in a fewer number of RN in the resistant genotypes‐grown soils. 08SS110‐NE06.OP exhibited greater vigor than PHY 490 W3FE in the later part of season. PHY 490 W3FE showed comparable yields with 08SS110‐NE06.OP despite differing in RN suppression and vigor in the later season. The information in this study could be useful to select resistant lines superior in yields and RN suppression as a parent for the development of RN resistant cultivars in cotton. Core Ideas Resistant genotypes were consistent in suppressing reniform nematode population over years. Resistant genotypes exhibited superior growth than commercial check in some instances. Commercial check showed comparable yields to resistant genotypes.

Plant-parasitic nematodes (PPNs) are vital soil organisms well-known to damage and reduce crop yield worldwide. Surveys were attempts to determine the impact of weed species on the communities and composition of nematodes in barley, wheat, quinoa, eggplant, and tomato crops in Alexandria and Ismailia regions of Egypt. During the surveys, eight occurring genera of nematodes were found namely; Meloidogyne spp, Pratylenchus spp, Helicotylenchus spp, Rotylenchulus spp, Xiphinema spp , Criconemoides spp, Ditylenchus spp , and Longidorus spp associated with the soil’s rhizosphere of 28 weed species belonging to 12 families. Among these weeds, Hordeum marinum and Sonchus oleraceus were good hosts to nematode species. Both wheat and barley had higher nematode diversity than quinoa in the winter season. Pratylenchus spp , Meloidogyne spp and Rotylenchulus spp can be considered vital potential PPNs with economic importance. Nematode abundances and structural indices varied greatly based on the host weed species, crop types and soil characteristics. A positive correlation was monitored among weeds, nematode frequencies and relative abundances as well as their crops. Finally, weed species are critical components in nematode communities that may increase the incidence and severity of nematode risks based on crop type and soil characteristics. Therefore weeds should be managed properly to diminish reservoir sites when developing nematode management options.

ABSTRACT Strategies for conserving natural resources and reducing agricultural inputs are the great challenge for agriculture, such as sustainable alternatives to control agricultural pests of high economic impact, e.g. plant-parasitic nematodes. This work aimed to evaluate phytonematode’s population dynamics in common bean cultivation grown under crop rotations and no-tillage system. The maize was seeded under pearl millet straw and intercropped with three different crops systems: i) exclusive maize system, ii) maize intercropped with brachiaria and, iii) maize intercropped with crotalaria. The experimental design was a randomized complete block with three treatments (crops systems) and 4 blocks (5 subsamples each block). The common bean was seeded on the straw of exclusive or intercropped maize. The phytonematode population was evaluated in the soil and in the roots in seven moments: (i) fallow; (ii) pearl millet flowering; (iii) pearl millet maturity; (iv) maize flowering; (v) maize maturity; (vi) common bean flowering; and (vii) common bean maturity. The greatest control of the phytonematodes species described in the area was in the maize intercropped with crotalaria treatment, as the phytonematodes population decreased 2.49-fold in this treatment when compared to exclusive maize, resulting in an increase of 11.27% in common bean yield. Therefore, maize intercropped with crotalaria is a viable alternative to reduce phytonematodes infestation in common bean crop.

The reniform nematode ( Rotylenchulus reniformis Linford & Oliveira) is a serious pathogen of Upland cotton ( Gossypium hirsutum L.) wherever it is grown throughout the United States. Upland cotton resistance to R . reniformis derived from the G . barbadense accession GB713 is largely controlled by the Ren barb2 locus on chromosome 21. Ren barb2 has proven useful as a tool to mitigate annual cotton yield losses due to R . reniformis infection; however, very little is known about the molecular aspects of Ren barb2 -mediated resistance and the gene expression changes that occur in resistant plants during the course of R . reniformis infection. In this study, two nearly isogenic lines (NILs), with and without the Ren barb2 locus, were inoculated with R . reniformis and RNAs extracted and sequenced from infected and control roots at 5-, 9-, and 13-dai (days after inoculation). A total of 966 differentially expressed genes (DEGs) were identified in the resistant NIL while 133 DEGs were discovered from the susceptible NIL. In resistant plants, biological processes related to oxidation-reduction reactions and redox homeostasis were enriched at each timepoint with such genes being up-regulated at 5- and 9-dai but then being down-regulated at 13-dai. DEGs associated with cell wall reinforcement and defense responses were also up-regulated at early timepoints in resistant roots. In contrast, in susceptible roots, defense-related gene induction was only present at 5-dai and was comprised of far fewer genes than in the resistant line. ERF, WRKY, and NAC transcription factor DEGs were greatly enriched at 13-dai in resistant roots but were absent in the susceptible. Cluster analysis of resistant and susceptible DEGs revealed an ‘early’ and ‘late’ response in resistant roots that was not present in the susceptible NIL. SNP analysis of transcripts within the Ren barb2 QTL interval identified five genes having non-synonymous mutations shared by other Ren barb2 germplasm lines. The basal expression of a single candidate gene, Gohir.D11G302300, a CC-NBS-LRR homolog, was ~3.5-fold greater in resistant roots versus susceptible. These data help us to understand the Ren barb2 -mediated resistance response and provides a short list of candidate resistance genes that potentially mediate that resistance.

Tunisian olive cultivation constitutes one of the principal economical and agricultural strategic sectors. In order to increase olive production, the olive management systems are changing towards intensification with irrigation, the introduction of new varieties, the use of intercropping, and high inputs of pesticides and fertilizers. These practices may create an environment more favorable to soil borne pathogens and plant-parasitic nematodes. Therefore, this study was performed to explore for the first time the plant-parasitic nematodes infesting olive roots and their diversity in the main producing areas of olive in Tunisia including 123 olive orchards. It aims also to determine which agronomic factors influence the multiplication and the diversity of plant-parasitic nematode communities. These investigations identified 11 genera of plant-parasitic nematodes viz. Criconemoides spp., Helicotylenchus spp., Heterodera spp., Meloidogyne spp., Paratylenchus spp., Pratylenchus spp., Rotylenchulus spp., Rotylenchus spp., Tylenchorhynchus spp., Tylenchus spp., and Zygotylenchus spp. It is revealed that the intensification of olive orchards with irrigation and the association of intercrops are the main agronomic factors influencing the multiplication and the diversity of plant-parasitic nematodes infecting olive trees. In particular, olive orchards under super-intensive regimes are more conducive to the multiplication of Pratylenchus spp. while the presence of irrigated intercrops enhances the multiplication of Meloidogyne spp.. Therefore, for the establishment of new olive orchards, it is suggested to choose certified olive plants and avoid infested soils or intercrops that can host dangerous nematodes.

Reniform nematode (Rotylenchulus reniformis, Linford and Oliveira) is a sedentary, semi-endoparasite that infects a wide range of plant hosts and is one of the top three nematode pathogens affecting soybean in the southeastern United States. Previous studies have linked resistance to reniform nematode in soybean to two quantitative trait loci on chromosomes 11 and 18. A Kompetitive Allele-Specific PCR (KASP) assay was designed using SNP markers within these two regions to distinguish reniform nematode-resistant soybean based on genotype. A collection of 44 soybean plant introductions with resistant phenotype to reniform nematode and 40 susceptible soybean lines were genotyped at the two target loci to validate the KASP assay design. Of the 44 observed resistant lines, two carried the susceptible genotype; PI 438489B at the locus on chromosome 18 and PI 495017C on chromosome 11. Of the 40 observed susceptible soybean lines, only 25 had the expected susceptible genotype at the loci on chromosome 18 and 13 on chromosome 11. Our KASP assay was 68% accurate in predicting the phenotype of 84 soybean accessions based on their genotype at the SNP marker on chromosome 18 and 83% accurate at chromosome 11. These results indicate a moderate correlation of soybean SNP markers GlyREN18_46 and GlyREN11_190 with reniform nematode resistance. Further research is required to improve the accuracy of KASP assays to predict soybean response to reniform nematode, particularly host susceptibility.

The identification of molecular markers that are closely linked to gene(s) in Gossypium barbadense L. accession GB713 that confer a high level of resistance to reniform nematode (RN), Rotylenchulus reniformis Linford & Oliveira, would be very useful in cotton breeding programs. Our objectives were to determine the inheritance of RN resistance in the accession GB713, to identify SSR markers linked with RN resistance QTLs, and to map these linked markers to specific chromosomes. We grew and scored plants for RN reproduction in the P₁, P₂, F₁, F₂, BC₁P₁, and BC₁P₂ generations from the cross of GB713 x Acala Nem-X. The generation means analysis using the six generations indicated that one or more genes were involved in the RN resistance of GB713. The interspecific F₂ population of 300 plants was genotyped with SSR molecular markers that covered most of the chromosomes of Upland cotton (G. hirsutum L.). Results showed two QTLs on chromosome 21 and one QTL on chromosome 18. One QTL on chromosome 21 was at map position 168.6 (LOD 28.0) flanked by SSR markers, BNL 1551_162 and GH 132_199 at positions 154.2 and 177.3, respectively. A second QTL on chromosome 21 was at map position 182.7 (LOD 24.6) flanked by SSR markers BNL 4011_155 and BNL 3279_106 at positions 180.6 and 184.5, respectively. Our chromosome 21 map had 61 SSR markers covering 219 cM. One QTL with smaller genetic effects was localized to chromosome 18 at map position 39.6 (LOD 4.0) and flanked by SSR markers BNL 1721_178 and BNL 569_131 at positions 27.6 and 42.9, respectively. The two QTLs on chromosome 21 had significant additive and dominance effects, which were about equal for each QTL. The QTL on chromosome 18 showed larger additive than dominance effects. Following the precedent set by the naming of the G. longicalyx Hutchinson & Lee and G. aridum [(Rose & Standley) Skovsted] sources of resistance, we suggest the usage of Ren barb¹ and Ren barb² to designate these QTLs on chromosome 21 and Ren barb³ on chromosome 18.

The reniform nematode, Rotylenchulus reniformis , is a sedentary root parasite that poses a significant threat to agricultural production in tropical and subtropical regions worldwide. In 2021–2022, a population of R. reniformis was identified in a melon greenhouse in Jimo District, Qingdao, China. To characterize this population, we employed morphological, morphometric, and molecular methods, which confirmed the identity of the nematodes as R. reniformis . Our investigation revealed that R. reniformis successfully infected the roots of melon plants and laid eggs, which could have led to significant crop damage. This report represents the first documented example of R. reniformis infecting melon plants in China. We evaluated several control strategies to combat this nematode, and our results indicated that soil solarization and the use of fosthiazate or chitooligosaccharide copper in combination with soil solarization were effective measures for managing R. reniformis in a greenhouse setting. In addition, combining soil solarization with chitooligosaccharide copper promoted melon plant growth and increased the relative abundance of microorganisms with biocontrol potential.