Root-knot Nematode Populations Research Articles

Efficacy of nematicides, Tricuran-P (Trichoderma harzianum T-22) and chicken manure on cucumber root-knot nematode populations, plant growth and soil enzyme activities

Efficacy of nematicides, Tricuran-P (Trichoderma harzianum T-22) and chicken manure on cucumber root-knot nematode populations, plant growth and soil enzyme activities

Identification and Characterization of a Virulent Meloidogyne incognita Population Breaking Tomato Mi-1-Mediated Resistance in Indiana

High-tunnel production is increasing rapidly in the US due to its effectiveness in extending production seasons. Tomato is considered one of the most profitable crops grown in high tunnels. The elevated soil temperature and constant soil moisture in high tunnels lead to the buildup of root-knot nematodes (RKNs). Growing RKN-resistant tomato cultivars or grafting onto RKN-resistant tomato rootstocks is considered effective in managing RKNs. However, all of the RKN-resistant tomato cultivars or rootstocks carry the same resistance gene, Mi-1. This lack of diversity in resistance has led to the emergence of virulent RKN populations breaking tomato Mi-1 resistance. Here, we identified and characterized a virulent population of Meloidogyne incognita from a high tunnel in Indiana. The M. incognita population was confirmed as being able to infect and reproduce on two resistant tomato cultivars, Better Boy and Early Girl, carrying the Mi-1 gene, under a controlled environment at 24 °C. To our knowledge, this is the first report of a virulent M. incognita population breaking Mi-1 resistance in Indiana. Virulent M. incognita populations overcoming Mi-1 resistance were previously reported in California and Georgia in the US. This work emphasizes the importance of regularly monitoring RKN population virulence to sustainably manage the pest.

Biocontrol Potential of Bacteria Isolated from Vermicompost against Meloidogyne incognita on Tomato and Cucumber Crops

Root-knot nematodes are the major diseases in protected cultivation around the world. Bio-organic fertilizer has become a research hotspot, with a variety of microorganisms that control various vegetable soil-borne diseases. This study screened nematocidal microorganisms from fresh vermicompost, explored the inhibitory substances produced by biocontrol agents, and evaluated their potential biocontrol ability in the pot and field under greenhouse conditions. The highly effective antagonistic microbes of Meloidogyne incognita (M. incognita) were screened. Strains YL1 and YL31 were identified as Peribacillus frigoritolerans, and strain YL6 was identified as Lysinibacillus fusiformis. The three strains all produced chitinase and protease, which prevented the normal development of eggs and the second-stage juveniles (J2) by destroying their appearance. The three strains all improved potassium-dissolving ability, and the strains YL1 and YL6 also enhanced phosphorus-dissolving ability. Pot experiments showed that tomato root knots were reduced, and plant growth improved. Field tests showed that the root-knot index and nematode population were reduced significantly, and cucumber growth and yield were enhanced. Strain YL1 had the best control effect with 70.6%, and the yield increased by 14.9% compared with the control. Overall, this study showed the ability of antagonistic bacteria YL1, YL6, and YL31 to control root-knot nematodes, and these antagonistic bacteria could be developed as biocontrol agents for sustainable agriculture.

Detection of Root-Knot Nematode Species and Races in Kahramanmaraş Province, Türkiye

Root-knot nematodes (Meloidogyne spp.) are organisms that spread over large areas and cause economic damage to vegetables. In this study, root-knot nematode populations obtained from vegetable growing areas of Kahramanmaraş province were identified. Overall, 132 root samples were taken from the vegetable crop fields. Root-knot nematode was detected in 25 of the collected samples and their diagnosis was determined based on biochemical (esterase isoenzyme phenotype), perineal pattern, and molecular methods. The race determination of root-knot nematodes was made according to the North Carolina Differential Host Test. Results showed that while Meloidogyne incognita was detected in Andırın, Onikişubat, Dulkadiroğlu, Türkoğlu, and Ekinözü districts of Kahramanmaraş, both M. incognita and M. javanica were found in Beyoğlu of Türkoğlu. This is the first report of M. javanica infection in Kahramanmaraş. Races of root-knot nematodes were determined as M. incognita race 1, race 2 and M. javanica race 2.

Effects of Soil Solarization and Grafting on Tomato Yield and Southern Root-knot Nematode Population Densities

High tunnel production has increased in the past 10 years in Kentucky with more than 1500 high tunnels constructed across the state. Tomato is the most popular and most valuable high tunnel crop per square foot. This has contributed to a lack of rotation and increased pressure from root-knot nematodes (RKN; Meloidogyne spp.). Infection by RKN leads to root galling and reduces the host plant’s ability to take up water and nutrients. Sustainable strategies are needed to manage increasing RKN populations for long-term health of high tunnel soils. Soil solarization is a nonchemical management strategy that has shown promise in other regions and in open field systems. Because tunnels are primarily used to produce high-value crops and are often used for season extension, solarizing during the off-season would be the most beneficial for growers because solarizing would require taking the tunnel out of production. The primary objective of this study was to determine whether springtime soil solarization in Kentucky high tunnels followed by use of resistant tomato cultivars is a viable and effective management strategy for RKN populations. Soil solarization was performed in two commercial high tunnels naturally infested with southern RKN (Meloidogyne incognita) for 2, 4, and 6 weeks and compared with a nonsolarized control. Soil temperatures reached during solarization were assessed at 7.6-, 15.2-, and 22.8-cm soil depth. After solarization, tomato was transplanted, including ‘Cherokee Carbon’ grafted onto RKN-resistant rootstocks ‘Fortamino’ and ‘Estamino’, RKN-resistant nongrafted ‘Caimon’, and susceptible ‘Cherokee Carbon’ as the control. The highest soil temperature achieved was 50 °C during 6 weeks of solarization at 7.6-cm soil depth compared with 38 °C reached in nonsolarized soil. Soil population densities of RKN increased each month after solarization and were generally lower after solarization with resistant tomato cultivars. The interaction of soil solarization and tomato cultivars was significant with respect to RKN densities in soil and roots. The mean RKN soil and root population densities in the nonsolarized, nonresistant treatment combination was significantly greater compared with all other treatments (P < 0.0001). Population densities of RKN were significantly higher in the nonsolarized control compared with solarized treatments (P = 0.0002). Nongrafted ‘Cherokee Carbon’ had significantly more RKN in surrounding soil compared with all other tomato treatments. Tomato yield was unaffected by soil solarization, but there were significant differences based on tomato cultivars alone; nongrafted ‘Cherokee Carbon’ yielded less than the resistant ‘Caimon’. Together, solarization and resistant cultivars reduced RKN population densities in soil and roots, which can provide growers with a nonchemical approach for long-term RKN management and high tunnel resiliency.

Evaluation of fluopyram for disease and root knot nematode control along with yield response on peanut

Efficacy of in-furrow application of fluopyram + imidacloprid alone or followed by fluopyram + prothioconazole at-pegging and aldicarb for managing peanut root-knot nematode populations, root and pod galling due to nematodes, and yield, along with non-target effects on leaf spot diseases and stem rot were compared on the root-knot susceptible cultivar Georgia-06G over seven years on an irrigated site with an established population of Meloidogyne arenaria race 1. In all years, fungicides were applied to all plots following a Peanut Rx application schedule. Root-knot nematode populations, nematode damage, and yield along with leaf spot severity and stem rot incidence significantly differed among years; except for nematode populations, these measured variables also differed by nematicide treatment. Averaged over years, galling and root damage was significantly reduced with aldicarb compared to the no-nematicide control but not with either of the fluopyram treatments. While similar late-season root-knot nematode populations were noted for all nematicide programs and the non-treated control, pooled over years, significant yield gains were obtained with aldicarb and fluopyram programs with the two-treatment program providing greater yields than the aldicarb treatment. Leaf spot severity, averaged over years, was similar in aldicarb and control treatments; however, both fluopyram treatments had significantly lower leaf spot severity than the aldicarb treatment. Stem rot incidence did not differ among nematicide treatments. In addition, pooled over years, there was a negative relationship between juvenile populations and yield, but this was relatively weak. Weather, particularly extreme rain conditions, impacted yield directly as well as indirectly by affecting leaf spot severity and nematode activity.

Nematicidal Effect of Certain Agrochemicals, Nutritional Compounds and Bio-Agents on The Population of Root-Knot Nematode (Meloidogyne Spp.) Infecting Potato

Nematicidal Effect of Certain Agrochemicals, Nutritional Compounds and Bio-Agents on The Population of Root-Knot Nematode (Meloidogyne Spp.) Infecting Potato

Effects of allyl isothiocyanate fumigation on medicinal plant root knot disease control, plant survival, and the soil bacterial community

BackgroundAllyl isothiocyanate (AITC) is a natural product with high volatility that is used as a biofumigant to alleviate soil-borne plant diseases, and problems such as root knot nematodes (RKNs) that necessitate continuous cropping. However, little research has assessed the effects of AITC fumigation on medicinal plants.ResultsAITC significantly reduced the population of RKNs in soil (p < 0.0001) and showed an excellent RKN disease control effect within 6 months after sowing Panax notoginseng (p < 0.0001). The seedling survival rate of 2-year-old P. notoginseng was approximately 1.7-fold higher after soil treatment with AITC (p = 0.1008). 16S rRNA sequencing indicated that the AITC treatment affected bacterial richness rather than diversity in consecutively cultivated (CC) soil. Furthermore, biomarkers with statistical differences between AITC-treated and untreated CC soil showed that Pirellulales (order), Pirellulaceae (family), Pseudomonadaceae (family), and Pseudomonas (genus) played important roles in the AITC-treated group. In addition, the microbiome functional phenotypes predicted using the BugBase tool suggested that AITC treatment is more conducive to improving CC soil through changes in the bacterial community structure. Crucially, our research also suggested that AITC soil treatment significantly increases soil organic matter (p = 0.0055), total nitrogen (p = 0.0054), and available potassium (p = 0.0373), which promotes the survival of a succeeding medicinal plant (Polygonatum kingianum).ConclusionAITC is an ecologically friendly soil treatment that affects the top 10 bacterial richness but not diversity. It could also provide a basis for a useful agricultural soil management measure to alleviate soil sickness.

Detection and counting of root-knot nematodes using YOLO models with mosaic augmentation

Root-knot nematodes (RKN) are microscopic plant parasites that cause significant economic damage to crops and vegetables. Accurate assessment of RKN populations is required for effective management of this disease. Several “You Only Look Once” (YOLO versions 2 to 7) architectures were investigated for the application of RKN enumeration in microscopic images. YOLOv5-608 model attained Precision score of 0.960, Recall of 0.951, F1-score of 0.990, mAP of 0.972 without mosaic augmentation. Using mosaic dataset, this was increased to Precision of 1.00, Recall of 0.998, F1-score of 0.999, and mAP of 0.995. YOLOv5-608 model showed the highest correlation between the manual and machine counting of RKN: coefficient of determination (R2) of 0.991, root mean square error (RMSE) of 0.313, and coefficient of variation (CV) of 0.251. For free-living nematodes (FLN), this resulted in R2 of 0.994, RMSE of 0.058, and CV of 1.760. YOLOv7-608 achieved the highest correlation between manual and machine counting of overlapped RKN (R2 of 0.970, RMSE of 0.595, and CV of 0.123). In addition, this study explored a new application of mosaic augmentation to analyse microscopic images acquired with different objective lense magnifications. The proposed framework supports the rapid assessment of plant parasitic nematodes necessary to implement nematode control strategies and improve crop management practices.

A muscadine locus confers resistance to predominant species of grapevine root-knot nematodes (&lt;i&gt;Meloidogyne&lt;/i&gt; spp.) including virulent populations

Root-knot nematodes (RKNs) Meloidogyne spp. are extremely polyphagous pests and four species severely affect grapevines throughout the world: M. arenaria, M. incognita, M. javanica and M. ethiopica. Californian populations of M. arenaria and M. incognita are reported to be virulent to widely used rootstocks and to the rootstock ‘Harmony’ in particular. Breeding RKNs-resistant grape rootstocks is a promising alternative to highly toxic nematicides. Muscadine (Vitis rotundifolia syn. Muscadinia rotundifolia) is a resistance (R) source with undercharacterised genetics. To this end, we used a segregating progeny between the RKN-resistant Vitis x Muscadinia accession ‘VRH8771’ from the muscadine source ‘NC184-4’ and the RKN-susceptible V. vinifera cv. Cabernet-Sauvignon. We first phenotyped its resistance to isolates of the i) M. arenaria, ii) M. incognita and iii) M. javanica species, and then to iv) two mixed Harmony-virulent Californian populations of M. arenaria and M. incognita. Finally, we created an isolate of M. arenaria and M. incognita from these Harmony populations and phenotyped the progeny to each of them [v) and vi)], and to vii) an isolate of M. ethiopica. The resistance phenotype of all the progeny’s individuals was independent of the RKN isolates or populations used. Resistance was mapped in a region of chromosome 18 in VRH8771, supporting the hypothesis that it is conferred by a single gene with an unprecedented wide spectrum in grapevine, including Harmony-virulent isolates. This dominant gene, referred to as MsppR1, is linked to the telomeric QTL XiR4 for X. index resistance from the same source. Additionally, plant mortality data showed that MsppR1-resistant material expressed a high-level resistance to the Harmony-virulent isolates. Our results are a first step towards the development of marker-assisted breeding using SSR and SNP markers for resistance to RKNs in accession VRH8771.

Management of Root-Knot Nematode on Okra through Bio-Agents

A pot study was conducted to assess the efficacy of various fungal and bacterial antagonists as seed coating treatments against Meloidogyne javanica, a root-knot nematode that infects okra plants. The seeds of okra cv. Pusa Sawani were subjected to treatments with Trichoderma viride, Purpureocillium lilacinum, and Pseudomonas fluorescens at a rate of 2 g/kg seed. As a comparison, Carbosulfan 3G was used as a control, applied at a rate of 3g/kg soil. The treated seeds were then planted in soil infested with two second-stage juveniles of the root -knot nematode per gram of soil. After 45 days of sowing, it was observed that the okra plants exhibited enhanced growth, while the population of root-knot nematodes was significantly reduced in all treatment groups compared to the untreated control. Among the different bio agents tested, Purpureocillium lilacinum exhibited the best treatment followed by Trichoderma viride and Pseudomonas fluorescens for increase plant growth characters as well as reduced nematode reproduction.

A Novel Robust Screening Assay Identifies Pseudomonas Strains as Reliable Antagonists of the Root-Knot Nematode Meloidogyne incognita.

Forty-four bacterial strains isolated from greenhouse soil and beetroots were tested for their antagonistic activity against the plant-parasitic root-knot nematode (RKN) Meloidogyne incognita, which causes significant yield losses in a number of important crops worldwide. Through a novel combination of in vitro and on planta screening assays, Pseudomonas spp. 105 and 108 were identified as the most promising bacterial isolates. Both strains were evaluated for their potential to control different RKN population densities and as root protectants against nematode infestation. Regardless of the application method, both strains significantly reduced root galling caused by M. incognita. These two strains were subjected to whole genome sequencing and de novo genome assembly as a basis for phylogenetic and future functional characterization. Phylogenetic analysis revealed that both Pseudomonas strains cluster within the Pseudomonas fluorescens clade among previously characterized RKN antagonists and Pseudomonas-based biocontrol agents of plant diseases.

Population of root knot nematode, Meloidogyne incognita and yield in tomato using various \bio agents under pot culture conditions

Tomato (Solanum lycopersicum) is one of the most important vegetable which has a great economic importance and also has a high processing value. Tomatoes are susceptible to root-knot nematode (Meloidogyne incognita) leading to a great economic loss. The life cycle of root-knot nematode takes about 25 days to complete. Second stage juveniles J2 initiate infection in the host. Root-knot nematodes constitute a major group of plant-parasitic nematodes causing extensive economic damage ton early all crop plants of economic importance in both tropical and sub-tropical crop production regions all over the world (Sikora and Fernandez, 2005). The efficacy of different bioagents like Trichoderma viride, Bacillus subtilis, Pochoniachlamy disporia, Purpureocillium lilacinum against Meloidogyn eincognita was estimated under four replications and assessment of plant morphometric characters and root knot index under pot culture conditions has been recorded. All the four bioagents were tested in vitro to study their efficacy against Meloidogyne incognita. Among all the bioagents tested, Purpureocillium lilacinum treatment showed significant increase in root length and shoot length (40.20cm and 76.20cm, respectively) and the untreated control plants recorded the least roo tlength and shoot length (19.11cm and 21.30cm). All the treatments were found to reduce nematode population in roots and highest reduction was noticed in Purpureocillium lilacinum treated plants (178.50 and 141.20) soil (250g) and root (5g), respectively. The untreated plants recorded the highest nematode population of 1314.14 and 1411.20 in soil (250g) and root (5g), respectively. Significant reduction in root knot index (1.2) were observed in the treatment Purpureocillium lilacinum and Carbofuran which recorded (2.0 ) per cent. The untreated control plant roots showed root knot index of 5.00 percent.

Distribution and population density of plant parasitic nematodes in Kallakurichi, Vedaranyam and Bargur blocks of Tamil Nadu

India contribute 9 per cent share in world production and one of the main vegetables grown in Tamil Nadu. Major production area of Tamil Nadu is Coimbatore, Dharmapuri, Salem and Krishnagiri districts. In India an average, a national loss of Rs. 21,068.73 millions has been estimated due to plant parasitic nematodes. An overall average annual yield loss in major horticultural crops due to nematodes goes upto 60% under protected cultivation. Protected cultivation is an emerging technology for raising vegetable and flower crops under controlled environmental condition and continuous growing of crops. Plant parasitic nematodes has emerged as a major problem, causing enormous yield loss. The maximum population of Pratylenchus spp in soil and root (300.54 and 275.50) were recorded in Veerasolapurammadur village, Kallakurichi block in sugarcane eco system and maximum lesion index 5.0 was recorded in same location and no incidence for root knot nematode was recorded. In Vaedharanyam block, The maximum population of Melodogyne graminicola in soil and root (300.25 and 325.65) were recorded in Neivellakku village, Vedharanyam block in rice eco system and maximum root knot index 5.0 was recorded in same location and no incidence for Aphelenchoides besseyi was recorded. In Barugur block ,The maximum population of lesion nematode, Radopholus similis in soil and root (450.20 and 410.25) were recorded in Santhur village, burgur block in banana eco system and maximum root lesion index 5.0 was recorded in same location and minimum population of root knot nematode (110.20 and 120.54) was recorded in Errapatty village of Burgur block.

Assessment on population of root knot nematode, Meloidogyne incognita and yield in brinjal using various bio agents under pot culture conditions

Brinjal (Solanum melongena) is one of the most important vegetables which has a great economic importance and also has a high processing value. Brinjals are susceptible to root-knot nematode (Meloidogyne incognita) leading to a great economic loss. The life cycle of root-knot nematode takes about 25 days to complete. Second stage juveniles J2 initiate infection in the host.Root-knot nematodes constitute a major group of plant-parasitic nematodes causing extensive economic damage to nearly all crop plants of economic importance in both tropical and subtropical crop production regions all over the world (Sikora and Fernandez 2005). The efficacy of different bioagents like Trichoderma viride, Bacillus subtilis, Pochoniac, hlamydosporia, Purpureocillium lilacinum against Meloidogyne incognita was estimated under four replications and assessment of plant morpho metric characters and root knot index under pot culture conditions has been recorded. All the four bio agents were tested in vitro to study their efficacy against Meloidogyne incognita. Among all the bioagents tested, Purpureocillium lilacinum treatment showed significant increase in root length and shoot length (35.11cm and 59.11cm, respectively) and the untreated control plants recorded the least root length and shoot length (12.02 cm and 15.12cm). All the treatments were found to reduce nematode population in roots and highest reduction was noticed in Purpureocillium lilacinum treated plants (161.11 and 138.10) soil (250g) and root (5g), respectively. The untreated plants recorded the highest nematode population of 1129.11 and 1259.20 in soil (250g) and root (5g) respectively. Singnificant reductionin root knot index (1.0) were observed in the treatment Purpureocillium lilacinum and Carbofuran which recorded (2.2 ) per cent. The untreated control plant roots showed a root knot index of 5.00 percent.

Assessment on population of root knot nematode, Meloidogyne incognita and yield in brinjal using various bio agents under pot culture conditions

Brinjal (Solanum melongena) is one of the most important vegetables which has a great economic importance and also has a high processing value. Brinjals are susceptible to root-knot nematode (Meloidogyne incognita) leading to a great economic loss. The life cycle of root-knot nematode takes about 25 days to complete. Second stage juveniles J2 initiate infection in the host.Root-knot nematodes constitute a major group of plant-parasitic nematodes causing extensive economic damage to nearly all crop plants of economic importance in both tropical and subtropical crop production regions all over the world (Sikora and Fernandez 2005). The efficacy of different bioagents like Trichoderma viride, Bacillus subtilis, Pochoniac, hlamydosporia, Purpureocillium lilacinum against Meloidogyne incognita was estimated under four replications and assessment of plant morpho metric characters and root knot index under pot culture conditions has been recorded. All the four bio agents were tested in vitro to study their efficacy against Meloidogyne incognita. Among all the bioagents tested, Purpureocillium lilacinum treatment showed significant increase in root length and shoot length (35.11cm and 59.11cm, respectively) and the untreated control plants recorded the least root length and shoot length (12.02 cm and 15.12cm). All the treatments were found to reduce nematode population in roots and highest reduction was noticed in Purpureocillium lilacinum treated plants (161.11 and 138.10) soil (250g) and root (5g), respectively. The untreated plants recorded the highest nematode population of 1129.11 and 1259.20 in soil (250g) and root (5g) respectively. Singnificant reductionin root knot index (1.0) were observed in the treatment Purpureocillium lilacinum and Carbofuran which recorded (2.2 ) per cent. The untreated control plant roots showed a root knot index of 5.00 per cent.

Population of root knot nematode, Meloidogyne incognita and yield in tomato using various \bio agents under pot culture conditions

Tomato (Solanum lycopersicum) is one of the most important vegetable which has a great economic importance and also has a high processing value. Tomatoes are susceptible to root-knot nematode (Meloidogyne incognita) leading to a great economic loss. The life cycle of root-knot nematode takes about 25 days to complete. Second stage juveniles J2 initiate infection in the host. Root-knot nematodes constitute a major group of plant-parasitic nematodes causing extensive economic damage ton early all crop plants of economic importance in both tropical and sub-tropical crop production regions all over the world (Sikora and Fernandez, 2005). The efficacy of different bioagents like Trichoderma viride, Bacillus subtilis, Pochoniachlamy disporia, Purpureocillium lilacinum against Meloidogyn eincognita was estimated under four replications and assessment of plant morphometric characters and root knot index under pot culture conditions has been recorded. All the four bioagents were tested in vitro to study their efficacy against Meloidogyne incognita. Among all the bioagents tested, Purpureocillium lilacinum treatment showed significant increase in root length and shoot length (40.20cm and 76.20cm, respectively) and the untreated control plants recorded the least roo tlength and shoot length (19.11cm and 21.30cm). All the treatments were found to reduce nematode population in roots and highest reduction was noticed in Purpureocillium lilacinum treated plants (178.50 and 141.20) soil (250g) and root (5g), respectively. The untreated plants recorded the highest nematode population of 1314.14 and 1411.20 in soil (250g) and root (5g), respectively. Significant reduction in root knot index (1.2) were observed in the treatment Purpureocillium lilacinum and Carbofuran which recorded (2.0 ) per cent. The untreated control plant roots showed root knot index of 5.00 per cent.

Differential Responses of Antioxidant Enzymes and Lignin Metabolism in Susceptible and Resistant Sweetpotato Cultivars during Root-Knot Nematode Infection.

Root-knot nematodes (RKN) cause significant damage to sweetpotato plants and cause significant losses in yield and quality. Reactive oxygen species (ROS) play an important role in plant defenses, with levels of ROS-detoxifying antioxidant enzymes tightly regulated during pathogen infection. In this study, ROS metabolism was examined in three RKN-resistant and three RKN-susceptible sweetpotato cultivars. The antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were assessed, as was lignin-related metabolism. In RKN-infected roots, both resistant and susceptible cultivars increased SOD activity to produce higher levels of hydrogen peroxide (H2O2). However, H2O2 removal by CAT activity differed between cultivars, with susceptible cultivars having higher CAT activity and lower overall H2O2 levels. In addition, the expression of phenylpropanoid-related phenylalanine ammonia-lyase and cinnamyl alcohol dehydrogenase genes, which encode enzymes involved in lignin metabolism, were higher in resistant cultivars, as were total phenolic and lignin contents. Enzyme activities and H2O2 levels were examined during the early (7 days) and late (28 days) phases of infection in representative susceptible and resistant cultivars, revealing contrasting changes in ROS levels and antioxidant responses in the different stages of infection. This study suggests that differences in antioxidant enzyme activities and ROS regulation in resistant and susceptible cultivars might explain reduced RKN infection in resistant cultivars, resulting in smaller RKN populations and overall higher resistance to infection and infestation by RKNs.

Effects of Planting Date, Cultivar and Vernalization Using Gibberellic Acid on the Severity of Root-Knot Nematode Damage to Globe Artichoke in Subtropical Sandy Soil.

Globe artichoke (Cynara cardunculus var. scolymus L.) is a new alternative crop in Florida. This long-season crop poses a very high risk of root-knot nematode (RKN) damage, the most important nematode problem in vegetable production in Florida. This study aimed to examine the impact of RKN damage on artichoke production in the subtropical climate of Florida. Treatments consisted of four cultivars ('Green Globe Improved', 'Green Queen', 'Imperial Star', and 'Opal') planted on three different dates (October 5, October 19, and November 2) in Experiment 1, and three cultivars ('Green Globe Improved', 'Green Queen', and 'Imperial Star') grown with or without vernalization using gibberellic acid (GA3) in Experiment 2. Both field experiments were conducted on sandy soil in west-central Florida during the 2020-2021 and 2021-2022 growing seasons. We collected RKN population density and gall index (GI) data to assess RKN damage. In Experiment 1, all tested cultivars showed moderate to high RKN infection in the 2021-2022 season, with 43% to 75% of roots galled. There was no effect of planting dates on RKN damage in the 2020-2021 season. However, delaying the planting date from October 5 to November 2 reduced the RKN damage while increasing the RKN population densities in the 2021-2022 season. In Experiment 2, all tested cultivars showed high RKN infestation, with more than 80% of roots galled. Vernalization by GA3 did not affect the severity of RKN damage. Our results suggest that all tested artichoke cultivars are highly susceptible to RKN in subtropical environments of Florida, raising an alarm on the risk of RKN damage to commercial artichoke production and increasing awareness about the need for RKN management.

Discerning host plant resistance sources in common bean (Phaseolus vulgaris) against root-knot nematode (Meloidogyne javanica) infection

From this study we could conclude that, resistant cultivars are the single effective solution to the management of root-knot nematode population to avoid crop losses. Also, it is essential to use resistant cultivars in situations where nematodes are present and when control is advantageous to yields. However, the reported moderately resistant cultivars, viz. Gujarat Rajmash, Amber (IPR 96-4) and HUR15 belong to secondary gene pool with cross-compatibility to cultivated common bean. Therefore, it may be further used in the pre- breeding programme for developing resistant common bean cultivars against root knot nematodes.