Pratylenchus Brachyurus Research Articles

Pratylenchus brachyurus parasitism on soybean: effects on productivity, vegetative and nematological parameters and chemical properties

The aim of this work was to evaluate the effect of Pratylenchus brachyurus parasitism on the vegetative and nematological parameters of soybean, as well as on the productivity, composition, isoflavone profile and antioxidant capacity of the grains. A completely randomized design with four nematode inoculum levels (0, 500, 1000 and 2000) was used. Plants without P. brachyurus presented higher productivity and lower values for vegetative parameters. Maximum reproduction of P. brachyurus (17,493 nematodes) was observed with the initial population of 1444 nematodes. With increasing inoculum level, the moisture, fiber, lipid and stachyose contents were reduced, while ashes, fructose, and sucrose levels were increased. The total phenolic compounds, total flavonoids and antioxidant capacity increased until an inoculum level of 1000 nematodes was reached. The highest concentration of isoflavones, namely, daidzein, genistin, genistein, glicitin, and acetyl-glicitin was detected at the inoculum level of 2000 nematodes. Therefore, the inoculum levels of P. brachyurus affected soybean development, as well as, the chemical composition of the grains.

Penetration and development of Pratylenchus brachyurus in maize roots treated with acibenzolar-S-methyl

The aim of this study was to evaluate the application of acibenzolar-S-methyl (ASM) in the penetration, development, and multiplication of P. brachyurus in maize. For this, maize seedlings cv. AL Bandeirantes, after 10 days of germination, were inoculated with 800 nematodes. Part of the plants were treated with ASM sprayed at the dose 0.25 g a.i. L−1, while another part were inoculated but not treated. Every five (experiment 1) and two (experiment 2) days after treatment (DAT), the plants were removed, the roots washed and stained with acid fuchsin for counting nematodes. The nematodes were also quantified at 30 and 60 DAT, and their length measured using an eyepiece graticule coupled to the optical microscope, in which the nematodes were classified in three groups: 0.10 to 0.29, 0.30 to 0.49 and 0.50 to 0.69 mm. ASM reduced the final nematode population in maize roots at 30 and 60 DAT, and the number of juveniles, adults and eggs in the plant root system at 8 and 10 DAT. In relation to the nematode development, an increase in the proportion of nematodes at an early stage (0.10 to 0.29 mm) and a lower proportion of nematodes presenting between 0.50 and 0.65 mm of length were observed in plants treated with ASM compared to control. Therefore, results suggest that the product studied may affect the development and reproduction of the nematode.

Nodal vine cutting technique for assessing nematode resistance in yams

Identifying resistance to plant-parasitic nematodes in yams is a major challenge in yam breeding programmes due partly to insufficient planting material (tubers) for evaluation. Susceptible yam cultivar, TDr 93-31 was inoculated with 0 (control), 200, 500, 1000 and 2000 eggs/individuals each of Meloidogyne incognita, Scutellonema bradys and Pratylenchus brachyurus. Vine cuttings of two cultivars each of Dioscorea rotundata, D. alata and D. dumetorum were compared to conventional minisett method in a second experiment. Planted vines and minisetts were inoculated with 500 and 5000 eggs/individuals respectively. Data were collected on percentage vine survival, fresh root and tuber weight, number of tubers and nematode population and damage. Vine survival was not significantly different between control and inoculated vines. Maximum damage rating (>60%) was observed with initial inoculum of 1000 eggs of M. incognita and 200 individuals of S. bradys and P. brachyurus. The two cultivars of D. alata and D. rotundata developed visible symptoms and supported nematode reproduction while the D. dumetorum cultivars did not. The reaction of yam cultivars planted as vines was consistent with results from conventional minisett method. The lowest inoculum of 200 egg/juveniles was sufficient to elicit a reaction from vines in the vertical sack system.

Morphological and molecular characterization of Pratylenchus species from Yam (Dioscorea spp.) in West Africa.

The root-lesion nematodes (RLN), Pratylenchus spp., are among the major plant-parasitic nematodes affecting yam (Dioscorea spp.) production in West Africa. The distribution and diversity of RLN species associated with yam was investigated through a soil and tuber survey of the main producing areas in Nigeria and Ghana. Pratylenchus spp. were detected in the yam rhizosphere in 59% of 81 soil samples from Ghana and 39% of 114 soil samples from Nigeria. Pratylenchus spp. were detected in 24 of 400 tubers examined, in combination with root-knot nematodes (Meloidogyne spp.) and their associated damage of galls and crazy roots (79%), and with yam nematode (Scutellonema bradys) and their associated damage of dry rot (17%), although no specific additional symptoms were observed for Pratylenchus spp. Species of Pratylenchus were identified by their morphological features and by sequences of the D2-D3 region of the 28 S rDNA gene and the mitochondrial cytochrome oxidase I gene (COI). Pratylenchus brachyurus was the most frequent RLN species in both the rhizosphere and tubers of yam. Pratylenchus hexincisus was recovered from one tuber collected in Nigeria. While further investigations are required to establish the host status of yam for this nematode, this appears to be the first record of P. hexincisus on yam. The present taxonomical status of P. scribneri and P. hexincisus is discussed.

Crotalaria species in succession to soybean for the management of Pratylenchus brachyurus

ABSTRACT: Soybean is the main agricultural crop in the State of Mato Grosso do Sul, Brazil. It is primarily cultivated in a crop succession system, in wich soybean is grown in spring/summer, followed by corn or graminaceous pastures in autumn/winter as a second crop. Due to the intensive cultivation, new phytosanitary problems have arisen, among them the root-lesion nematode, Pratylenchus brachyurus, which besides causing damage to plant roots, can be important gateway for other soil pathogens. The recent occurrence of high nematode population densities has brought great concern due to the limited resistant soybean genotypes available. Besides, the use of nematicides only reduces nematodes populations temporarily. A viable alternative for the control of soil nematodes could be the use of Crotalaria spp. in succession or rotation with soybean. Crotalaria is immune or a bad host to the nematode, besides having high capacity of biological nitrogen fixation. Thus, the objective of the present research was to define the best way of insertion of this legume as a second crop in soybean production systems to reduce the population density of the root-lesion nematode. Two experiments were carried out: one in the field, in an infested area, and other in a greenhouse. In both experiments, the treatments were: 1) Zea mays, 2) Brachiaria brizantha cv. Xaraés,, 3) Z. mays + Crotalaria spectabilis, 4) Z. mays + C. ochroleuca, 5) B. brizantha cv. Xaraés + C. spectabilis, 6) B. brizantha cv. Xaraés + C. ochroleuca, 7) C. spectabilis, and 8) C. ochroleuca. The effect of the treatments was evaluated by estimating the number of nematodes in the roots of autumn/winter crops, as well as in the roots of the soybean cultivated in the sequence. The cultivation of both Crotalaria species provided suppression of the nematode population. However, when intercropped with corn or Xaraés palisade grass, the suppressive effect of Crotalaria was supplanted by corn and Xaraés palisadegrass susceptibility to the root-lesion nematode.

Plant-parasitic nematodes associated with the root zone of hop cultivars planted in a Florida field soil.

In early 2016, hop plants were introduced into Florida. By late 2016, the hop plants were showing stunted growth and were heavily parasitized by Meloidogyne javanica. In this study, we determined host susceptibility of 14 hop cultivars to M. javanica in a greenhouse experiment and monitored population development of plant-parasitic nematode species in the root zone of 17 hop cultivars planted in three newly established hop yards in Florida. Plant-parasitic nematodes in the rooting zone soil of field grown hop plants included M. javanica, Pratylenchus brachyurus, Paratrichodorus minor, Belonolaimus longicaudatus, Xiphinema setariae/vulgare complex, Mesocriconema xenoplax, and Helicotylenchus dihystera; however, soil population densities of P. minor, B. longicaudatus, X. setariae/vulgare complex, M. xenoplax, and H. dihystera remained low through the study. Root galling, M. javanica egg production, and soil population densities of M. javanica were consistently large on the ‘Canadian Red Vine’, ‘Centennial’, ‘Chinook’, and ‘Comet’ cultivars, and small on the ‘Galena’ and ‘Triple Perle’ cultivars. No differences were observed in soil population densities of P. brachyurus among hop cultivars. Overall, our study provides the first report of plant-parasitic nematode population development in the root zone on hop cultivars planted in Florida.

Biological Control Associated With Plant Nutrition for Meloidogyne javanica and Pratylenchus brachyurus Management in Soybean

Meloidogyne javanica and Pratylenchus brachyurus stand out among the main nematodes in soybean crops. Research on integrated management are often conducted, due to the low efficiency of the main control methods when they are applied alone. Thus, the aim of the present study was to assess the potential of biological control and plant nutrition products to control these nematodes in soybean. The effect of each product alone on nematode hatching and mortality was also assessed. A greenhouse experiment was also carried out, evaluating five doses of the product for biological control based on Bacillus and Trichoderma, with and without the presence of the product for nutrition, inoculated with 2000 eggs and juveniles for the gall nematode or 1000 specimens for the nematode lesions. After 30 days of multiplication, the aerial part was removed and the soil was revolved to receive the new sowing of the soybean with the respective treatments mentioned above. After 60 days, the experiments were evaluated for nematological parameters. Both products reduced hatching and increased nematode mortality. Treatments with biological control were efficient in reducing M. javanica and P. brachyurus, mainly when applied at doses close to 5 and 8 kg ha-1, respectively. The nutrition product negatively influences the biological control.

Resistance to Pratylenchus brachyurus in Vitis species population through multivariate approaches and mixed models

ABSTRACT: Genetically diverse interspecific hybrids of Vitis were selected for resistance to Pratylenchus brachyurus. Three segregating populations with 57 hybrid crosses were evaluated. The parents included Vitis romanetiiC166-043 × 07355-075, 06354-047 × Cereza and 06354-047 × Nocera, selected from the germplasm bank at the University of California, Davis, the United States. The experiment was arranged in a randomized block design, with three replications and three plants per plot. Root mass, nematodes per gram of root and reproduction factor were determined and used as quantitative variables; 16 multi categoric descriptors were also evaluated. The traits were analyzed using the Ward-Modified Location Model procedure (Ward-MLM) for the composition of genotype groups. Genetic parameters and prediction of genetic values by Restricted Maximum Likelihood / Best Linear Unbiased Prediction (REML / BLUP) were assessed. The Ward-MLM classification strategy supported the formation of three homogeneous groups. Group I comprised 13 hybrids; Group II, 26 hybrids; and Group III, 18 hybrids. Groups II and III contained hybrids resistant to P. brachyurus. High broad sense heritability values were found for root mass, reproduction factor and nematodes per gram of root, which provided genetic gain and allowed selection of resistant genotypes available for cloning, since the total genetic variance occurred due to the dominance effects. Of the 57 genotypes assessed, those with the lowest genotypic values for reproduction factor were selected as resistant, including: CH3.2, CH3.23, CH3.8, CH3.37, CH3.38, CH3.41, CH3.36, CH2.1, CH2.7, CH1.1, CH1.3 and CH1.2.

Agentes de biocontrole no manejo de Pratylenchus brachyurus na cultura da soja

The root-lesion-nematode, Pratylenchus brachyurus, is considered one of the main pathogens of soybean crop in the Brazilian Cerrado. The objective of this work was to evaluate the potential of different fungi species in the management of P. brachyurus in soybean. A completely randomized design, in a factorial scheme (4 x 4 + 2), consisting of four species of fungi: Beauveria bassiana, Trichoderma harzianum, Metarhizium anisopliae and Paecilomyces lilacinus, with four forms of application (in seed, furrow, seed + furrow and cover) and two additional controls (water and nematicide), with five replicates was used. Soybean plants cv. Soy Tech 820 RR were inoculated with 50000 eggs and second stage juveniles (J2) of P. brachyurus. After 60 days of application of the treatments, parasitism and agronomic evaluations were performed on soybean. The fungi used in the control, influenced positively in almost all the vegetative characteristics of the plants, promoted by the marked reduction of the number of juveniles in the root and in the soil and, mainly, by the decrease in the number of eggs in the roots. The forms of application did not directly influence the action of the biocontrol agents and all microorganisms behaved in a protective way, making it impossible or slowing the nematodes parasitism on the roots of the plants.

Filter Pie in the Control of the Nematoid of Root Lesions in the Soybean and Corn

The efficiency of waste from industrial processing has been increasingly studied in the control of phytonematoids, especially filter cake, coffee husks and sugar cane bagasse. The objective of this study was to evaluate the effect of organic residues through the use of filter cake to reduce the population density of Pratylenchus brachyurus (Tylenchida: Pratylenchidae). The first experiment was conducted in a greenhouse in the completely randomized design in the 2 × 4 factorial scheme (soybean genotypes vs. filter cake doses) with four replications using soybean genotypes AS 3810 IPRO and LG60163 IPRO and the second experiment was carried out under the same conditions, with maize AG 1051 with four doses of filter cake with 7 replications. In both experiments, the planting was carried out in an area located in the city of Goianésia, Goiás, Brazil. The results showed that the population density of Pratylenchus brachyurus in the maize crop to grow AG 1051 did not show statistically significant difference by applying the different doses of filter cake. In soybean genotypes AS 3810 IPRO and LG60163 IPRO were affected in ways contrary to phytonematoid infestation, in which AS 3810 IPRO showed a population increase according to the increase of the applied amounts of filter cake, whereas in the cultivar LG60163 IPRO there was a decrease for doses of 10 tonnes/ha-1 and 30 tonnes/ha-1, with an increase of only 20 tonnes/ha-1.

Phytonematodes in Integrated Crop-livestock Systems of Tropical Regions

The integrated crop-livestock system (ICLS) is a model of sustainable cultivation that allows the recovery of degraded pastures and the intensification in pasture and grain production. However, the presence of pathogens in the production fields has hampered the employment of these systems. In order to minimize or eradicate the phytonematodes in the production fields and the seeds used in CLIS, it is necessary to know the nematofauna. Based on this, this work aimed to perform a literature review describing the main forages and agricultural crops used in integrated crop-livestock systems in tropical regions, the major phytonematodes associated with these crops and their control measures. This work was based on a literature review from the Scielo, Scopus and Google Scholar databases, with data from 1999 to 2019. The initially used keywords were "tropical weeds"; "Agricultural crops"; and "ICLS" and their respective terms in the Portuguese language. From the initial results, we used the keywords "Brachiaria syn. Urochloa sp. "; "Phytonematodes"; "Millet"; "Maize"; "Panicum sp."; "Soy"; "Sorghum", and "ICLS" and their respective terms in the Portuguese language. Publications that did not meet the criteria of this study (analyzed by titles and abstract) were considered as exclusion criteria, as well as repeated works in the databases. Based on the literature, the cultivation of forages belonging to the genera Brachiaria syn. Urochloa sp. and Panicum sp., along with and soybean, maize, sorghum and millet are predominant in the ICL system of tropical regions. The phytonematodes Meloidogyne sp., Pratylenchus brachyurus, Heterodera glycines, Rotylenculus reniformis, Aphelenchoides sp., Ditylenchus sp. and Filenchus sp. cause greater severity of damage to the main cultures used in ICL. No control method can eradicate the phytonematodes. The most effective control for the studied phytonematodes is through integrated pest and disease management.

New innovations in ‘Queen’ pineapple production in South Africa

Pineapple cultivation in South Africa has been growing to an industry where 95% of the local fresh market is supplied by the ‘Queen’ pineapple growers. Increasing production costs and relatively low consumer consumption (less than 1.6 kg fruit capita‑1 year(‑1)) have forced the farmers to farm smarter and maximize production inputs. Close collaboration with pineapple researchers has led to improved as well as new practices. The collaboration involved the diagnostic service project of the Hluhluwe Research Station, the bi-annual block competition amongst farmers and the pineapple growers study group. The diagnostic services offered by the Hluhluwe Research Station is an initiative to improve ‘Queen’ pineapple production by identifying problem areas. Results of the service are used to understand the population dynamics of the pests subjected to the cultivation practices applied by each grower. Nematodes, and in particular the lesion nematode (Pratylenchus brachyurus), and mealybug (Dismycoccus brevipes) are considered major pests in ‘Queen’ pineapple production. The effect of the factors influencing pest control strategies are evaluated for each farmer and control strategies are optimized. The most important aim of the bi-annual block competition is to stimulate innovation by exploring new concepts on a specific aspect of cultivation. These innovative ideas are then refined in a research project or certain research aspects will be tested in a project and can then be optimized in a block competition. By multiplying specific trial concepts on the farms of the study group members, results can be compared and the influence of factors such as soil type, crop history and topography can be established in a relatively short period.

Distribuição espacial de Pratylenchus brachyurus em área de soja no Leste do Maranhão

The root-lesion nematode, Pratylenchus brachyurus, is native to the Brazilian Cerrado region. Although soybean is not a natural host of this nematode, its advance on Cerrado areas has made this species become an important pathogen for the crop. This study aimed to assess the spatial distribution of P. brachyurus and its influence on soybean crop productivity in eastern Maranhao. For this, a sampling was conducted in 142 georeferenced points distributed in an area of 180 × 180 m. Plant and soil samples were collected, being the nematodes extracted and counted. Spatial patterns were estimated using geostatistical analysis. Anisotropic exponential models were adjusted for all studied variables with higher ranges in the direction of soil tillage and planting (135°). The increase in nematode population, as well as its spatial pattern, was related to the presence of roots of the host plant in the soil. The direction of soil tillage and planting influenced the distribution of nematodes in the area, being the main controlling factor of their spatial patterns.

Molecular genetic diversity in segregates of Vitis: implications for the breeding of grapevine aiming at resistance to Pratylenchus brachyurus

This study presents a grapevine breeding project that examines technologies for the development of new cultivars with a view to combining nematode resistance with desirable agronomic traits. The objectives of this study were to undertake a genetic-molecular characterization of a segregating population with resistance to the nematode P. brachyurus, resulting from hybridizations between different selections of Vitis, and to indicate superior segregants for future crosses. Seventy-four interspecific hybrids, seven parents, and variety Niagra were used. The genomic DNA of each individual was extracted by the CTAB method, and 10 microsatellite markers were employed. The number of fragments per primer ranged from 2 to 4. Mean observed heterozygosity (0.52) was higher than expected heterozygosity (0.42), and the fixation index averaged − 0.230. These values indicate broad genetic variability and are within the expected limits for grapevine, considering that the best performances are obtained with heterozygous individuals maintained through vegetative propagation. The genetic distance calculated by the weighted index and represented by dendrogram based UPGMA method resulted in the formation of five groups. Groups IV and V stood out with the highest number of individuals. Group IV had approximately 6% of its individuals with greater genetic similarity to the parents of V. vinifera origin. The largest group (Group V) had approximately 82% of its individuals with greater similarity to the parents of V. vinifera origin. Interspecific hybrids resistant to P. brachyurus and genetically closer to one of the parents of Vitis vinifera origin will be selected for future crosses, enabling the continuity of the grapevine breeding program.

Management Alternatives for Pratylenchus brachyurusin the Soybean Crop

In the Maranhão cerrado, Pratylenchus brachyurus phytonematoid is present in soybean plantation areas, occurring significant losses. At this aspect, the aim was to evaluate the effect of crop succession in the reduction of population and damage of P. brachyurus on soybean. Treatments consisted of soybean cultivation on soybean (T1, control) and soybean cultivated in succession on the “straw” of Crotalaria ochroleuca (T2), C. spectabilis + millet ‘ADR 300’ (T3), millet ‘ADR 300’ T4), Brachiaria ruziziensis (T5), maize ‘GNZ 2005’ + B. ruziziensis (T6) and maize ‘GNZ 2005’ (T7). The following characteristics were evaluated: P. brachyurus infestation in soil and plant height, plant height, productivity, number of plants per plot, number of pods per m², number of pods per plant, number of grains per plant, number of grains per pod, mass of a thousand grains, total mass and dry matter The highest populations of P. brachyurus have been found in conventional soybean cultivation on soybean, or when grown on maize straw ‘GNZ 2005’, B. ruziziensis and maize ‘GNZ 2005’ + B. ruziziensis. In turn, small populations of phytonematoid occurred in the succession of the soybean with C. ochroleuca, millet ‘ADR 300’ and systems consortium of these two cultures. In order to improve soybean yield in the Maranhão cerrado, it is recommended to use C. spectabilis during the off-season, as an option to reduce the population of P. brachyurus, as well as in the intercropped intercrop with ‘ADR 300’ millet and on its single crop.

BIOLOGICAL MANAGEMENT OF Pratylenchus brachyurus IN SOYBEAN CROPS

ABSTRACT The efficiency of biological products combined with biological fertilization for controlling Pratylenchus brachyurus in soybean crops, and effects of these treatments on soybean crops were evaluate. A greenhouse experiment was conducted at the Mato Grosso State University, in Brazil, using a randomized block design with a 10×2 factorial arrangement, and four replications. The treatments consisted of Trichoderma asperellum, B. subtilis, Purpureocillium lilacinum, B. subtilis + T. asperellum, B. subtilis + P. lilacinum, T. asperellum + P. lilacinum, B. subtilis + T. asperellum + P. lilacinum and abamectin, and Controls with, and without nematodes. Nematode population, plant height, stem base diameter, and soil microbiological characteristics (at 60 and 120 days after sowing - DAS), shoot dry weight (60 DAS), and number of pods per plant, and grain yield (120 DAS) were evaluated. The treatments were efficient for the control of phytonematodes at 60 DAS; the efficiency of treatments with biological products increased when combined with biological fertilization. The biological products were more efficient for controlling the nematodes than abamectin at 120 DAS; and the percentage of control were higher when they were combined with biological fertilization, in both growing periods. The biological treatments resulted in better agronomic characteristics, and higher number of pods per plant, and grain yield, affecting the plants in the first growing period, and significant interaction with the biological fertilizer for these variables in the second growing period. The interaction between treatments and biological fertilization was significant for soil microbiological characteristics in the second growing period.

English

The root lesion nematode (Pratylenchus brachyurus) is one of the main phytosanitary problems of cotton plants in Brazil. Searching for alternatives that minimize the damages in the crop, several methods are performed aiming to manage these damages. Among them, is the use of vegetal extracts. In this sense, the aim of this study was to evaluate the potential of black angico extract (Anadenanthera macrocarpa) in the management of P. brachyurus in cotton crop. The experiment was conducted in a greenhouse at the Phytopathology Laboratory of the Federal University of Piauí in Bom Jesus-PI. The experimental design was completely randomized, in a factorial scheme (2×6), composed of two sources of extracts (leaf and bark) of black angico under six concentrations (0, 20, 40, 60, 80 and 100 g L-1), with five replications per treatment. The plants were inoculated with 1900 specimen/juveniles and eggs, 96 h after the transplanting. Sixty days after the application of extracts, some agronomic variables of the cotton and P. brachyurus were evaluated. The volume and fresh root mass showed considerable gains for all concentrations with the leaf extract. The plant height was negatively influenced by concentrations above 60.83 g L-1 for both extracts. Regarding the parasitism, all the extract concentrations, regardless of the source (leaf or bark), showed suppressiveness to P. brachyurus. Therefore, the aqueous extracts of black angico present nematicidal action and favor the development of cotton plants.   Key words: Gossypium hirsutum, root lesion nematode, alternative management. &nbsp

Host suitability of grain sorghum and sudangrass for Pratylenchus brachyurus

ABSTRACT: Nowadays, the root-lesion nematode Pratylenchus brachyurus (Godfrey) is a major pest of soybean in Brazil, mainly in areas using double cropping with maize or cotton, which are suitable hosts for P. brachyurus. A great effort has been made to find cash crops for P. brachyurus management. Grain sorghum [Sorghum bicolor (L.)] was classified as a non-host for P. brachyurus but based on a single trial. It would be a valuable option as a culture for double cropping with soybean, as it is profitable and can be used in root-lesion nematode management. Sudangrass (S. bicolor var. sudanense) is not directly profitable, but Brazilian farmers favor it because it can produce pasture, green chop, silage, or hay under unfavorable hydric conditions. However, no information is available regarding the suitability of sudangrass for P. brachyurus. Thus, the current study aimed to assess the suitability of grain sorghum and sudangrass for P. brachyurus in two glasshouse trials. The first trial tested sudangrass and grain sorghum ‘DKB 510’, ‘Dow 740’, ‘Dow 822’, ‘DKB 599’, and ‘AG 1040’. The second trial retested sudangrass and grain sorghum ‘Dow 740’ and ‘DKB 599’. The results demonstrated that sudangrass and grain sorghum were suitable hosts for P. brachyurus. These results, in addition to those obtained for other types of sorghum, emphasize that S. bicolor and sudangrass should be avoided in fields infested with P. brachyurus, as they increase the nematode population.

Evaluation of soybean breeding lineages to new sources of root-knot nematode resistance

ABSTRACT In Brazil, as the soybean crop expands the losses caused by nematodes as well as its incidence in producing areas have increased. Therefore, this work aimed to develop a non-genetically modified soybean which combines desirable traits as the root-knot nematode resistance, early-maturity, high seed yielding, and high oil and protein contents. Consequently, seeds (F2) derived from the double-crossing between (Guarani x Sambaiba) x (M Soy 6101 x Conquista) were bulked to grow the F3 generation. Following generations were advanced by the SSD method of breeding until F6. Thus, plants showing superior characteristics were planted separately to perform progeny tests and then advanced breeding lines were thoroughly tested and compared to standards in representative environments across several locations in the Midwestern region in Brazil. As a result, we developed an early-soybean with cycle-length of 107 days; usually cycles range from 90 to 160 days. It presents desirable traits as high yield (3677 kg ha-1), Brazilian national average ranged between 2.5 and 3 thousand kg ha-1; broad adaptability, with 19% of oil, and 38.4% of protein on the seeds. Oil and protein standard contents are 20% and 40%, respectively. In addition, it is root-knot nematode (Pratylenchus brachyurus) resistance, not differing statistically (RF = 1.70) from the expected value given by Crotalaria spectabilis (RF = 1.14). Accordingly, we recommend this new cultivar to producers that intend to grow a second crop of either corn or cotton in the summer, or for crop producing areas with high incidence of P. brachyurus.

Endogenous soybean peptide overexpression: an alternative to protect plants against root-knot nematodes

Nematodes are pathogens of many important crops, including soybean. The main species found in Brazil are root-knot (Meloidogyne spp.), cyst (Heterodera glycines), root lesion (Pratylenchus brachyurus) and reniform (Rotylenculus reniformis) nematodes. Ureases are traditionally known for catalyzing the hydrolysis of urea to ammonia and carbon dioxide. Besides the main function, they present other independent biological roles, including toxic activities against insects, specially Coleoptera and Hemiptera, and fungi. In previous work, the DNA sequence encoding an insecticidal peptide - named Jaburetox - was identified in a Canavalia ensiformes urease gene. The recombinant Jaburetox exhibited toxicity against insects. Subsequently, the DNA sequence corresponding to Jaburetox was identified as part of the soybean Eu4 urease gene, with the resulting peptide named Soyuretox. In the present study, explants of soybean were transformed with Agrobacterium rhizogenes and ‘composite’ plants produced consisting of wild-type shoots and transgenic hairy roots overexpressing Soyuretox. Thereafter soybean plants overexpressing Soyuretox were obtained through bombardment transformation. Due to similarity between nematode and insect digestion mechanisms, we challenged composite and whole-transgenic plants with the nematode Meloidogyne javanica. Hairy roots overexpressing Soyuretox exhibited a significant reduction (48 %; p<0.05) in the average reproductive factor when compared with empty-vector transformed hairy roots. Transgenic plants overexpressing Soyuretox also exhibited significant reduction (37.5 %; p<0.05) in reproductive factor when compared with non-transformed plants. This study demonstrates the potential of Soyuretox in confering resistance against nematodes, representing a new alternative control method for nematodes in economically important crops.