Michelly Ragazzi Cardoso

Resistance inducers in the control of root lesion nematodes in resistant and susceptible cultivars of maize

Pratylenchus brachyurus stands out among the major importance nematodes for the national agriculture, due your difficulty of control. Thus, the study aimed to evaluate the efficiency of resistance inductors in the nematode management in resistant and susceptible maize. It was studied the inductors acibenzolar-S-metil, Ecolife™ and manganese phosphite. The experiment was conducted in a factorial arrangement (2 × 4) composed for two maize genotypes (resistant and susceptible to nematode). Each inductor was applied, singly, seven days and one day before inoculation and seven days after inoculation to nematode. Untreated plants were used as control. The inductor Acibenzolar-S-metil was efficient to reduce the nematode population in both genotypes. Ecolife™ promoted the nematode reduction in susceptible genotype while the results were variable for manganese phosphite. In general, the inductors showed no significant effect on plant development and the same factor mainly affected by genotype.

Acibenzolar-S-methyl on Meloidogyne javanica control in lettuce

ABSTRACT Nematodes are among the main limiting factors of the vegetables productivity, especially due to management restriction this crop to obtain an efficient control of pathogen. Resistance induction using acibenzolar-S-methyl (ASM) has presented promising results in the management of diseases, but to plant-parasitic nematodes the time required to activate latent defense mechanisms is a limiting factor, which can be prevented with the treatment of seedlings in trays. Thus, the present study aimed to assess different times of ASM application to Meloidogyne javanica control in lettuce. Lettuce seedlings were produced in trays, transplanted to pots 25 days after germination and inoculated with 2000 eggs of the nematode. The seedlings were pulverized on shoots with ASM 10 or 5 days before of transplant (DBT), on the day of transplant (DT), 5 or 10 days after transplant (5 or 10 DAT), 10 DBT + DT and 10 DBT + 5 DAT. The untreated plants formed the control group. Fifty days later, these plants were collected and evaluated the nematological and vegetative parameters. The treatments promoted a decrease in M. javanica population higher than 60% when applied until 5 DAT and generally did not interfere with the vegetative parameters of lettuce, and ASM can be adopted as an alternative for the root-knot nematodes management.

Acibenzolar-S-methyl doses and application methods to Pratylenchus brachyurus control in maize

ABSTRACT Pratylenchus brachyurus is one of the main limiting factors of agricultural yield in annual crops, particularly due its difficult management. Methods to reduce populations are constantly sought, and the use of resistance inducers deserves attention. Thus, the study aimed to assess the effect of acibenzolar-S-methyl (ASM) application in different doses to P. brachyurus control in maize. Initially, 1000 specimens of P. brachyurus were inoculated in maize for the multiplication. After 60 days, the aerial part (AP) was discarded and maize was sown under the treatments: seed treatment (ST), application in the AP and ST + AP, in the doses of 0.125, 0.25, 0.5 and 1.0 g i.a./L. Vegetative and nematological parameters were assessed 60 days later. ASM did not affect plant growth, but reduced nematode population in all the treatments. The treatment methods did not differ and reduced the number of nematodes/g root by 64.25 to 80.14% compared to the control. The doses of 0.6, 0.51 and 0.65 g i.a./L promoted the most reductions in the number of nematodes/g root when applied in ST, AP and ST + AP, respectively. Thus, we recommend the use of ASM applied on shoot in a dose of 0.50 g i.a./L.

Host status and phenotypic diversity of rice genotypes in relation to Pratylenchus brachyurus resistance

The aim of this study was to assess the susceptibility of rice genotypes to Pratylenchus brachyurus and investigate the inheritance of resistance in the crop. Two experiments were conducted under controlled conditions, using naturally infested soil. Twenty-six rice genotypes were assessed, with maize used to show the susceptibility pattern. The maize was cultivated for 90 days and the initial nematode population was determined. Then, rice genotypes were cultivated, and the final nematode population and the reproduction factor (RF) were estimated 90 days after germination. All genotypes were susceptible to P. brachyurus in the two experiments but only one showed statistical differences, indicating variation in susceptibility, and genotypes Linhagem L03-107 and Cateto Amarelo scored higher than the control genotype, with RF of 8.80 and 9.48, respectively. Inheritance of resistance was poorly influenced by genotype genetics. Cluster analysis allowed the identification of five different groups of genotypes but there was low genetic variability among the genotypes.

Penetration of Pratylenchus zeae in antagonistic plants

Pratylenchus zeae Graham is one of the most important nematode species found in sugarcane and has been reported in the main sugarcane-producing regions of Brazil, especially in areas of commercial production in the state of São Paulo (Novaretti et al., 1998, Dinardo-Miranda et al., 2003), in the northeast region (Moura et al., 2000) and in Paraná (Severino et al., 2010). Due to the scarcity of plants resistant to root-lesion nematode and limitations regarding the use of chemical control, crop rotation is becoming increasingly important. Thus, the use of leguminous plants as a green manure is crucial as it promotes, among other benefits, improvements in the physical and chemical conditions of the soil (McSorley & Gallaher, 1994). An experiment was conducted in a glasshouse at Universidade Estadual de Maringá, campus Regional de Umuarama (State University of Maringa, Umuarama Regional Campus) in January 2014, with minimum and maximum temperatures of 20.2 and 32.4°C, respectively. The species assessed in this experiment were crotalaria (Crotalaria spectabilis), dwarf pigeon pea (Cajanus cajan), velvet bean (Mucuna aterrima), jack bean (Canavalia ensiformis) and stylosanthes (Stylosanthes capitata + S. macrocephala), with maize (Zea mays) cv. IPR 114 as control. The seedlings, produced in the same manner, were transplanted into 500 ml plastic containers of the