Peanut Root-knot Nematode Research Articles

Resistance to Tomato spotted wilt virus and Root‐Knot Nematode in Peanut Interspecific Breeding Lines

The peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] and Tomato spotted wilt virus (TSWV), genus Tospovirus, are economically significant pathogens of peanut (Arachis hypogaea L.) in the USA. Peanut cultivars are available that have resistance to either the peanut root‐knot nematode (PRN) or TSWV, but no cultivars are available that have resistance to both pathogens. The objective of this research was to identify peanut breeding lines that have resistance to both pathogens. We crossed interspecific peanut germplasm with two cultivars that are susceptible to both PRN and TSWV. Progenies were examined in a greenhouse screening system to measure resistance to PRN. Subsequently, this material was evaluated for resistance to TSWV in field plots. Ten breeding lines were identified which exhibited a reduction in nematode reproduction in comparison to the nematode susceptible check ‘Georgia Green’. These breeding lines also exhibited a reduction in incidence of TSWV in comparison to the TSWV susceptible check ‘COAN’. When grown in a field with pressure from both pathogens, these breeding lines had higher yield than cultivars with resistance to only one pathogen. This is the first report of peanut germplasm with resistance to both TSWV and the peanut root‐knot nematode and the first report of resistance to TSWV in interspecific peanut germplasm.

Management of the Peanut Root-knot Nematode, Meloidogyne arenaria, with Host Resistance

Management of the common peanut root-knot nematode has traditionally relied on treatment of infested fields with nematicides, as well as rotations with other crops. The availability of nematod-eresistant cultivars gives growers another option and will reduce the growers reliance on nematicides. The nematode-resistant peanut cultivars COAN and NemaTAM can be grown in nematode infested fields without having to rely on nematicide applications to achieve the genetic yield potential of the crop. Accepted for publication 28 October 2002. Published 21 November 2002.

Geographical Distribution of Genetic Diversity in Arachis hypogaea

Abstract The U.S. maintains a large (> 8000 accessions) and genetically diverse collection of peanut (Arachis hypogaea L.) germplasm. It is costly to screen all accessions within this collection for traits that could be useful in cultivar development. The objective of this research was to identify countries of origin that are rich sources of resistance to important peanut diseases. This would allow peanut breeders to focus their efforts on smaller subsets of the germplasm collection. Accessions in the peanut core collection were evaluated for resistance to late (Cercosporidium personatum Berk. & M. A. Curtis) and early (Cercospora arachidicola Hori) leaf spot, tomato spotted wilt Tospovirus (TSWV), the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1], and Cylindrocladium black rot (CBR)[Cylindrocladium crotalarie (Loos) Bell & Sobers]. These data then were examined to determine if genes for resistance clustered geographically. Several geographical areas that appear to be rich sources for disease-resistant genes were identified. China had a relatively large number of accessions with resistance to the peanut root-knot nematode. Peru appeared to be a rich source of material with resistance to CBR. Resistance to late leaf spot was more frequent than expected in accessions from Bolivia and Ecuador. Bolivia was also a valuable source of resistance to early leaf spot. Early leaf spot resistance also was more prevalent than expected in accessions from India, Nigeria, and Sudan. India, Israel, and Sudan were valuable origins for material with resistance to TSWV. Accessions with multiple disease resistance were most common in India, Mozambique, and Senegal. This information should enable plant breeders to utilize more efficiently the genes for disease resistance that are available in the U.S. germplasm collection.

Status of the Arachis Germplasm Collection in the United States

Abstract An extensive working collection of Arachis germplasm is maintained by the USDA at the Southern Regional Plant Introduction Sta. in Griffin, GA. Much of this collection is maintained also under long-term seed storage at the Nat. Seed Storage Lab. in Ft. Collins, CO. The working collection consists of 9027 accessions of A. hypogaea and 684 accessions of Arachis species. About half of the A. hypogaea accessions are unimproved landraces collected in the crop's centers of diversity in South America. The other half is comprised of germplasm obtained from countries outside of South America. The U.S. germplasm collection of peanut was the first major germplasm collection to have a working core collection. Research has verified that this core collection can be used to improve the efficiency of germplasm utilization. This has stimulated a great amount of germplasm evaluation work and has resulted in the identification of numerous sources of resistance to several economically significant pathogens. Considerable efforts in the U.S. also have been devoted to the use of wild species of Arachis for sources of resistance to pathogens. Programs are ongoing to introgress high levels of resistance or immunity to early (Cercospora arachidicola Hori) and late (Cercosporidium personatum Berk. & M.A. Curtis) leaf spots, nematodes, and viruses. Genetic resources have been particularly useful in adding disease resistance to peanut cultivars. This has had a significant economic impact on U.S. peanut farmers. The largest impacts have been from the development of cultivars with resistance to Sclerotinia blight (Sclerotinia minor Jagger), the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1], and tomato spotted wilt Tospovirus. Use of these resistant cultivars has an estimated economic impact of more that $200 million annually for U.S. peanut producers.

Timing of Aldicarb Applications to Control Meloidogyne arenaria in Peanut1

Abstract Four fieldtrialswere conductedin northwest Florida to determine the efficacyofaldicarb appliedat varyingtime intervals after planting on peanut (Arachis hypogaea) to manage the peanut root-knot nematode, Meloidogyne arenaria. Initial treatments with aldicarb (Temik 15G), fenamiphos (Nemacur 15G), and phorate (Thimet 15G) were made at planting of peanut cv. Southern Runner. The chemicals were applied as 20-cm-wide bands over the open seed furrow using a tractor-mounted Gandy applicator. Post-plant treatments were made with a Gandy applicator at time intervals from 28 to 104 dafter planting as 36-cm-wide bands over the row centers. Post-harvest M. arenaria population densities were affected little by any chemical treatment compared to the control. The efficacy of the chemical treatments was variable and averaged onlya 295-kglha yield increase for the single at-plant applications of aldicarb compared to the control. Allat-plant + post-plant aldicarb treatments increased yield over the control by an average of712 kg¡ ha. Results from these trials did not establish a single optimal time for post-plant application of aldicarb on peanut. Data from these tests, however, indicated that a post-plant aldicarb treatment can be applied latter than previously recommended in Florida.

Inheritance of Resistance to the Peanut Root-knot Nematode in Capsicum chinense

Greenhouse experiments determined the inheritance of resistance to the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] in Capsicum chinense Jacq. germplasm lines PA-353 and PA-426. Evaluation of parental, F1, F2, and backcross populations of the crosses PA-353 × PA-350 and PA-426 × PA-350 (PA-350 is a susceptible cultigen) indicated that resistance in both C. chinense germplasm lines was conditioned by a single dominant gene. Evaluation of the F1 × resistant parent backcross populations in the cytoplasm of their respective resistant and susceptible parents indicated that the cytoplasm of the resistant parent is not needed for full expression of resistance. Allelism tests indicated that the dominant resistance gene in both PA-353 and PA-426 is allelic to a resistance gene in C. annuum L. `Carolina Cayenne'. However, these allelism tests did not demonstrate conclusively that the M. arenaria race 1 resistance gene in C. chinense is the N gene that conditions resistance to the southern root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] in C. annuum. The ease and reliability of evaluating plants for resistance to root-knot nematodes and the availability of simply inherited sources of resistance makes breeding for peanut root-knot nematode resistance a viable objective in C. chinense breeding programs.

Expression of Nematode Resistance in Plant Introductions of Arachis hypogaea

Abstract The peanut root-knot nematode (Meloidogyne arenaria, race 1) is a world-wide pest of peanut (Arachis hypogaea L.). Several moderately resistant genotypes have been identified in the cultivated peanut species. Our objective was to determine the expression of resistance for six of these genotypes. We examined four potential expressions of resistance—(a) fewer second-stage juveniles (J2) penetrate the roots, (b) fewer J2 establish functional feeding sites, (c) slower maturation, and (d) reduced fecundity (eggs per female). Seedlings of the susceptible cultivar Florunner and the resistant genotypes were inoculated with J2 of M. arenaria, and transplanted 3 d later to synchronize nematode development. Penetration was assessed at 3 and 10 d; development at 10 (or 12), 17, 22, and 27 d; and fecundity at 60 d after inoculation. The experiments were conducted in a greenhouse or growth chamber. The number of J2 within the roots was similar in resistant and susceptible peanut after 3 d; however, numbers were lower in two of the resistant genotypes than in Florunner after 10 d. A greater percentage of J2 failed to develop in all of the resistant genotypes (72 to 79%) than in Florunner (50%) after 17 d. Of the J2 that did begin to develop, the rate of maturation and fecundity was similar in resistant and susceptible genotypes. A lack of development indicates that the J2 failed to establish a feeding site. Therefore, the primary expression of resistance in the six peanut genotypes appears to be a reduction in the percentage of J2 that establish a functional feeding site. The decline in J2 after infection may be related to the failure to establish a feeding site.

Genetic Analysis of Meloidogyne arenaria Race 1 Resistance in Tobacco

Inheritance of resistance to the peanut root-knot nematode (Meloidogyne arenaria (Neal) Chitwood race 1) was investigated in the flue-cured tobacco cv. Speight G 28 and the breeding lines 81-RL-2K and SA 1214. The genetic relationship of this resistance in Speight G 28 to the resistance of the same cultivar to races 1 and 3 of M. incognita was also studied. Crosses were made between the root-knot nematode-susceptible flue-cured tobacco cv. NC 2326 and the three resistant genotypes. Parental, F1, F2 and backcross generations (BC1P1, BC1P2) were grown for each cross in randomized complete block designs with five replications in the greenhouse. Data indicated that resistance to M. arenaria race 1 in the three resistance sources is conditioned by a single dominant gene, but this resistance is partial compared to that for M. incognita races 1 and 3. Further, resistance to races 1 and 3 of M. incognita and resistance to M. arenaria race 1 in cv. Speight G 28 appear to be controlled by the same gene. These results, combined with the absence of segregation in the F2 populations of the crosses between resistant parents 81-RL-2K × SA 1214, 81-RL-2K × Speight G 28, and SA 1214 × Speight G 28, suggest allelism of resistance among these genotypes.

Optimal rotation of peanuts and cotton to manage soil-borne organisms

Damage from the root-knot nematode ( Meloidogyne arenaria) and Southern blight (white mold) fungus ( Sclerotium rolfsii) are principal yield-limiting factors in the production of peanuts ( Arachis hypogaea) in the USA. Both are widespread in the southeastern USA and yield losses caused by them can be severe. Both organisms can be suppressed by pesticides, but both can also be suppressed by rotation with cotton and certain other crops. This article presents a stochastic dynamic programming model that maximizes the expected present value of profit over a multi-year planning horizon with production of peanuts and cotton, accounting for: (1) the stochastic population dynamics of the peanut root-knot nematode, Southern blight fungus, and beneficial microbivorous nematodes; (2) the stochastic market prices for cotton and peanuts; and (3) land use in each of the previous 2 years. Expected profit from this seven-state variable dynamic programming model is compared to expected profit for monoculture peanuts, monoculture cotton, three fixed rotations, and a myopic, but flexible, rotation. Comparison of expected returns for these decision models indicates that an information-based strategy—the optimal dynamic strategy or the myopic strategy—is better than any of the fixed rotations. The myopic strategy results in expected profits almost as high as the optimal strategy for this particular problem. Since a myopic strategy is much more easily computed and more easily explained to producers, it has much more promise for adoption than difficult-to-understand results from a stochastic dynamic programming model.

027 Genetic Analysis of Resistance to the Peanut Root-knot Nematode Exhibited by the Capsicum chinense Germplasm Line PA-353

The peanut root-knot nematode (Meloidogyne arenaria race 1) is potentially a major pest of pepper cultivars belonging to the species Capsicum chinense. Greenhouse tests were conducted to: 1) compare the level of resistance to the peanut root-knot nematode exhibited by the recently released C. chinense germplasm line PA-353 to that exhibited by the C. annuum cv. Carolina Cayenne; 2) to determine the inheritance of the resistance in the C. chinense germplasm line PA-353; and 3) to determine the genetic relationship between the resistance exhibited by the C. chinense germplasm line PA-353 and that exhibited by the C. annuum cv. Carolina Cayenne. The level of resistance exhibited by the C. chinense germplasm line PA-353 was equal to the high level of resistance of the C. annuum cv. Carolina Cayenne. Evaluation of parental, F1, F2, and backcross populations of the cross between the resistant C. chinense germplasm line PA-353 and the susceptible C. chinense accession PA-350 indicated that the resistance in C. chinense is conditioned by a single dominant gene. The F2 population of the interspecific cross between the resistant C. chinense germplasm line PA-353 and the resistant C. annuum cv. Carolina Cayenne did not segregate for resistance, indicating that the dominant resistance gene in C. chinense is likely allelic to or closely linked to a gene conditioning resistance in C. annuum. The availability of a simply inherited source of outstanding resistance makes breeding for peanut root-knot nematode resistance a viable objective in C. chinense breeding programs.

DNA marker analysis of loci conferring resistance to peanut root-knot nematode in soybean

Peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood] (Ma) is a serious pathogen of soybean, Glycine max L. Merrill, in the southern USA. Breeding for root-knot nematode resistance is an important objective in many plant breeding programs. The inheritance of soybean resistance to Ma is quantitative and has a moderate-to-high variance-component heritability on a family mean basis. The objectives of the present study were to use restriction fragment length polymorphism (RFLP) markers to identify quantitative trait loci (QTLs) conferring resistance to Ma and to determine the genomic location and the relative contribution to resistance of each QTL. An F2 population from a cross between PI200538 (Ma resistant) and ‘CNS’ (Ma susceptible) was mapped with 130 RFLPs. The 130 markers converged on 20 linkage groups spanning a total of 1766 cM. One hundred and five F2:3 families were grown in the greenhouse and inoculated with Ma Race 2. Two QTLs conferring resistance to Ma were identified and PI200538 contributed the alleles for resistance at both QTLs. One QTL was mapped at 0-cM recombination with marker B212V-1 on linkage group-F (LG-F) of the USDA/ARS-Iowa State University RFLP map, and accounted for 32% of the variation in gall number. Another QTL was mapped in the interval from B212D-2 to A111H-2 on LG-E, and accounted for 16% of the variation in gall number. Gene action for the QTL located on LG-F was additive to partially dominant, whereas the gene action for the QTL on LG-E was dominant with respect to resistance. The two QTLs, when fixed on the framework map, accounted for 51% of the variation in gall number in a two-QTL model. The two QTLs for Ma resistance were found in duplicated regions of the soybean genome, and the major QTL for Ma resistance on LG-F is positioned within a cluster of eight diverse disease-resistance loci.

Crambe and rapeseed meal as soil amendments: nematicidal potential and phytotoxic effects

Rapeseed and crambe meals, when added to soil infested with eggs of Meloidogyne arenaria, reduced the number of galls on tomato (‘Rutgers’) roots. Both meals, however, were phytotoxic to tomato and reduced the height of celosia, dianthus, and rose periwinkle plants, and resulted in lower germination of periwinkle seed. When the planting of tomato was delayed for 3 weeks after addition of 1% meals the phytotoxicity and root injury were diminished, but not alleviated. The ED50 for rapeseed meal against peanut root-knot nematode was determined to be 0.64% v v when added to piedmont soil and planting occurred immediately, or 0.86% when planting was delayed 1 week.

Identification and Evaluation of Additional Sources of Resistance to Peanut Root-knot Nematode in Arachis hypogaea L.1

Abstract The root-knot nematode (Meloidogyne arenaria race 1) causes significant economic losses throughout the peanut (Arachis hypogaea) production areas of the southern U.S. Chemicals for control of this pest are becoming increasingly limited, and there are no peanut cultivars with resistance. Seven moderately resistant plant introductions have been identified; however, less than 25% of the germplasm collection has been examined for resistance based on nematode reproduction. The objectives of this work were to examine an additional 1000 plant introductions for resistance to the peanut root-knot nematode and to compare the most resistant introductions to previously reported sources of resistance. Preliminary greenhouse screening trials were conducted to rate severity of root galling and amount of egg mass production. Seventeen accessions were selected based on a mean egg mass rating of less than or equal to three. These selections were reevaluated in additional greenhouse and field experiments to quantify levels of resistance and to directly compare these sources of resistance to those previously reported. Eight accessions had a significantly higher level of resistance (lower egg mass rating) than Florunner; however, none had a significantly higher level of resistance than those previously reported. Results of this study identified additional sources of resistance which may provide unique genes for resistance. In addition, two of these new sources of resistance (PI 298848 and PI 311265) exhibited significantly higher yield than those previously identified when grown in soil heavily infested with M. arenaria.

Identification of Peanut Genotypes with Improved Drought Avoidance Traits1

Abstract Peanuts (Arachis hypogaea L.) are often subjected to drought during some period in the growing season. A large root system may improve the plant's ability to continue growth during a drought. During greenhouse and field screening trials for resistance to the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood, race 1], 16 peanut genotypes were observed to have very large root systems. Using these 16 genotypes plus cultivars Florunner, Southern Runner, and germplasm line Tifton 8 as checks, several studies were conducted to evaluate these genotypes for drought avoidance characteristics. In the first study, root and shoot development were observed at 15-d intervals on plants grown from seed in sand-filled pots. In a second 2-yr study, selections were grown in the field under portable rain-exclusion shelters that created controlled periods of stress. In addition, the genotypes were also planted and observed in unsheltered naturally drought stressed field plots. In the sand-filled pot study, plant inventory (PI) numbers 315628, 268885, 318740, 269106, and 314893 developed the largest root systems. In the field drought stress studies, low visual stress ratings were recorded for Southern Runner, Tifton 8, PI 295722, and PI 315628. Low canopy temperatures characterized PI 315628, Tifton 8, and PIs 295722, 259637, and 268885. When averaged over three tests, sheltered (1991 and 1992) and unsheltered (1991), Tifton 8, PI 318740, Florunner, PI 315622, and PI 315628 produced the highest yields. Two of these higher yielding genotypes (Tifton 8 and PI 315628) had low stress and temperature ratings and PI 315628 also had the largest root system measured in this study.

Activity of Fosthiazate against Meloidogyne arenaria, Frankliniella spp., and Sclerotium rolfsii in peanut1

Abstract The efficacy of fosthiazate, a new organophosphorus compound, against the peanut root-knot nematode (Meloidogyne arenaria (Neal) Chitwood), thrips (Frankliniella spp.), and southern stem rot (Sclerotium rolfsii Sacc.) in peanut (Arachis hypogaea L.) was studied for 2 years at Tifton, Georgia. Different rates and methods of applying granular and emulsifiable concentrate formulations of fosthiazate were compared with rates and methods of applying granular fenamiphos and aldicarb which were included as standard treatments. When compared with untreated controls, all treatments of all compounds increased peanut yield and reduced nematode galls on peanut roots, pods, and pegs and thrips damage to foliage significantly in both years. The treatments, however, varied in their effects on southern stem rot. Peanut yields from plots treated with equal rates of the granular and emulsifiable concentrate formulations of fosthiazate were similar. Yields of plots treated with fosthiazate at different rates compared favorably with those treated with comparable rates of fenamiphos and aldicarb. Fosthiazate increased peanut yield as much as 214% in 1990 and 64% in 1991, but yields varied with rates applied.

Resistance to the Peanut Root-Knot Nematode (Meloidogyne arenaria) in Arachis hypogaea1

Abstract The peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] causes significant economic losses throughout the peanut (Arachis hypogaea L.) production area of the southern United States. Chemicals for control of this pest are becoming increasingly limited, and there are no known sources of resistance within the U. S. A. hypogaea collection. The objectives of this research were to screen 1,321 plant introductions for resistance or hypersusceptibility based on egg-mass ratings in greenhouse tests and to conduct more intensive greenhouse studies of selected genotypes to evaluate this method for identifying resistance to the peanut root-knot nematode. Twenty-seven genotypes with low and eight genotypes with high egg-mass ratings were selected and reevaluated in a more intensive greenhouse experiment. Seventeen of the low selections supported fewer (P≤0.05) egg masses, and seven supported less egg production per gram of fresh root weight than Florunner. Three selections for high egg-mass ratings supported more nematode eggs per plant than the cultivar Florunner and had a greater host efficiency. One of these genotypes supported more nematode eggs per gram of fresh root weight than Florunner. These results show that resistance to M. arenaria exists in the cultivated peanut species and can be selected by rating egg-mass production on greenhouse-grown plants.

A Technique for Screening Peanut for Resistance toMeloidogyne arenaria

Two hundred ninety-three peanut accessions were screened for resistance to the peanut root-knot nematode using visual galling and egg-mass ratings. Staining with phloxine B greatly expedited the egg mass screening process. No high level of resistance was observed in any of the accessions evaluated

Effect of some nematicides for control of peanut root-knot nematode

Effect of some nematicides for control of peanut root-knot nematode