Cristiano Bellé

Determination of photosynthetic pigments in fleabane biotypes susceptible and resistant to the Herbicide Glyphosate

Chlorophylls and carotenoids are the main photosynthetic pigment in plants. In the weeds, the greatest amount of photosynthetic pigments can result in high competitiveness of the species. The aim of this study was to quantify the content of photosynthetic pigments in biotypes of fleabane (Conyza bonariensis) susceptible and resistant to glyphosate, by two different methods, as well as a correlation between chlorophyll content obtained by portable and classical methodology (extractable chlorophyll). An experiment was conducted in greenhouse and laboratory, 2 x 5 factorial scheme, where factor A was equivalent to biotypes of fleabane (resistant and susceptible to glyphosate) and factor B to developmental stages plants (rosette vegetative I, II and III and reproduction). At all stages of development, fleabane plants were evaluated with the portable determiner (chlorophyll content) and then the same leaves were subjected to classical methodology laboratory (extractable pigments). The resistant biotype of fleabane showed higher contents of chlorophyll a, b, and total carotenoids, inferring a greater competitive potential regarding the susceptible population to the herbicide. The portable determiner of chlorophyll showed high correlation with the classical method of determination of photosynthetic pigments, and can thus be used to accurately assess this, saving time and reagents.

First Report of Meloidogyne ethiopica Parasitizing Sugarcane in Brazil

C. Bellé , Doutorando em Fitossanidade, Universidade Federal de Pelotas, 96010-900, Pelotas, RS, Brazil; S. M. Kulczynski, Universidade Federal de Santa Maria, Frederico Westphalen, 98400-000, RS, Brazil; P. R. Kuhn, EPAGRI, 89893-000, Mondaí, SC, Brazil; R. M. D. G. Carneiro, Embrapa Recursos Genéticos e Biotecnologia, 70770-91, Brasília, DF, Brazil; and I. Lima-Medina and C. B. Gomes, Embrapa Clima Temperado, 96010971, Pelotas, RS, Brazil.

Pó-de-basalto no desenvolvimento de plantas de alface e na dinâmica populacional de insetos

The aim of this work was to evaluate effect of the application of basalt powders from three different origins via soil (incorporation) and aerial (spraying) application in the performance of lettuce plants and in the population dynamics of phytophagous insects, respectively. Lettuce seedlings cv. Veronica at 8 days after emergence were transplanted to raised beds after the incorporation of the basalt powders. The effects on plant development were evaluated 50 days after transplantation and the parameters assessed were: plant height, growth of root system, dry mass, insertion diameter, volume of the root system and chlorophyll and carotenoid contents. Insect population dynamics was performed after the application of 100 g of basalt powder diluted in two liters of water (2 L ha) through four sprayings with intervals of 10 days between each. Sampling was performed daily and the insects collected were separated and identified. There was a significant increase in the variables plant height, growth of root system and dry mass in the treatments with the incorporation of basalt powder in the soil when compared to the control treatment. There was also a significant increase of 36% and 20% in the chlorophyll and carotenoid contents in lettuce leaves, respectively. There was no significant difference in the volume of the root system and insertion diameter between the treatments. The aerial spraying on lettuce plants with different basalt powders directly influenced the insect population dynamics with a significant decrease in the number of insects collected in all treatments.

Desempenho de sementes de soja tratadas com bioestimulante sob diferentes condições de potencial osmótico

O trabalho teve como objetivo verificar a influencia do tratamento de sementes com bioestimulante sob condicoes de diferentes potenciais osmoticos e seu efeito sobre o potencial fisiologico da semente e o desenvolvimento inicial da cultura da soja. Os tratamentos foram arranjados em esquema fatorial 2 x 5, sendo, presenca ou ausencia do bioestimulante, e cinco potenciais osmoticos (0,0; -0,3; -0,6; -0,9; -1,2 MPa), com quatro repeticoes. A qualidade fisiologica das sementes foi determinada atraves dos testes de germinacao - primeira contagem da germinacao; classificacao do vigor das plântulas; comprimento e materia seca da parte aerea e das raizes das plântulas. De acordo com os testes realizados, verificou-se que o decrescimo no potencial osmotico, induzido por solucao de NaCl, reduz a germinacao e o vigor de sementes de soja, e que o tratamento de sementes com bioestimulante proporciona aumento no desempenho de plântulas de soja e induz resistencia a condicoes de estresse hidrico.

First Report of Sclerotium rolfsii Causing Stem Rot of Luffa cylindrica in Brazil

Luffa cylindrica (L.) Roem. (Cucurbitaceae) is an Asian vine widely known as the source of loofah (Purseglove 1968). In Brazil (local name bucha), it is cultivated by small-scale producers as a cash crop. In February 2017, L. cylindrica plants with rotted and girdled stem bases were found in a commercial field (27°22′S; 53°25′W) in Frederico Westphalen, Rio Grande do Sul, Brazil. Disease symptoms later led to a collapse of stems. Necrotic areas were covered with white cotton mycelium as well as abundant spherical sclerotia. The fungus was isolated in pure culture by direct transfer of sclerotia in aseptic plates with potato dextrose agar (PDA). After 7 days, cottony white colonies started to appear, often forming fans, primary hyphae 2.0 to 5.0 μm in diameter, and bearing clamp connections; sclerotia formed after 10 days, initially white and becoming dark brown with age, and 0.65 to 2.15 mm in diameter. A specimen was deposited in the herbarium (Federal University of Pelotas Herbarium, Rio Grande do Sul State, Brazil) under accession no. LPS0025. Molecular characterization was performed by amplifying and sequencing the internal transcribed spacer (ITS) region using ITS1 and ITS4 primers (White et al. 1990) and the translation elongation factor (TEF-1α) gene region using primers EF595F and EF1160R (Wendland and Kothe 1997). Sequences of the studied DNA regions were submitted to GenBank (ITS: MF425542; and TEF-1α: MF434828). BLAST searches in GenBank showed 99 to 100% identity with the existing sequences of Athelia rolfsii (Curzi) C. C. Tu & Kimbr (anamorph: Sclerotium rolfsii Sacc.) (ITS: KU128903, KX139196, DQ059578, and GU080230; and TEF-1α: KM521767, JF267808, JF267798, and JF267798). To fulfill Koch’s postulates, 10 healthy, 20-day-old L. cylindrica seedlings were inoculated with sclerotia obtained from a 15-day-old culture. Dry sclerotia were placed directly at the base of the plant (four sclerotia per plant). Ten uninoculated L. cylindrica seedlings were used as the control treatment. The inoculated and uninoculated plants were incubated in a humid growth at 26°C for 24 h and then maintained in a greenhouse. Seven days later, pathogen-inoculated plants showed typical symptoms similar to those observed under natural conditions, but no symptoms were seen on the control plants. The pathogenicity tests were carried out three times. The fungus was reisolated from the artificially inoculated plants. According to morphological and molecular characteristic combinations, the isolate was confirmed as S. rolfsii. S. rolfsii has been reported on Citrullus lanatus, Cucumis sativus, Cucurbita pepo, and other species in the Cucurbitaceae family in Brazil (Queiroz et al. 2002), but not on Luffa cylindrica. To our knowledge, this is the first report of S. rolfsii causing disease on L. cylindrica in Brazil.

Detection of Meloidogyne arenaria in cucumber in Rio Grande do Sul state, Brazil

Diseased cucumber plants with symptoms of decline and root knots were collected from a crop in the municipality of Faxinal do Soturno, Rio Grande do Sul state, Brazil. Morphological (perineal patterns), biochemical (esterase phenotypes) and molecular (D2–D3 region) studies allowed to identify parasitizing nematodes, such as Meloidogyne arenaria. To our knowledge, this is the first report of Meloidogyne arenaria on Cucumber in Rio Grande do Sul State, Brazil.

REAÇÃO DE GENÓTIPOS DE CANA-DE-AÇÚCAR AO PARASITISMO DE Meloidogyne javanica E Pratylenchus zeae

The objective of this work was to evaluate the response of sugarcane genotypes to Meloidogyne javanica and Pratylenchus zeae. Sugarcane seedlings of the genotypes RB985944, RB987932, RB877935, RB855156, RB935744, RB996961, RB925345, RB935581 and RB966928 obtained from tissue cultures and maintained in pots with sterilized soil in a greenhouse were inoculated with 5,000 eggs + secondstage juveniles of M. javanica or 1,600 of P. zeae per plant, using six replicates per treatment. Tomato (Rutgers) and sorghum (BRS506) plants were used as control and proof of viability of the inoculum for the M. javanica and P. zeae, respectively. The number of root-knot in the plants inoculated with M. javanica, final nematode population and reproduction factor (RF) of both nematodes were evaluated at 120 days after inoculation. The averages of the different variables were compared by the Scott-Knotts clustering test at 5%. The nematodes M. javanica and P. zeae showed RF>1.00 in all sugarcane genotypes assessed, however, different levels of susceptibility were found. The lowest reproduction of the nematodes was found in the genotypes RB008347, RB877935, RB975944 and RB987932 (M. javanica) and RB987932 and RB966928 (P. zeae).

Control of wheat stink bugs (Hemiptera: Pentatomidae) in southern Brazil using the fungus Metarhizium anisopliae

Stink bugs of the species Nezara viridula and Dichelops melacanthus are considered as some of the main insect pests associated with wheat production in Brazil. The use of the entomopathogenic fungus Metarhizium anisopliae might be an alternative for the management of these insects with chemical insecticides. Thus, the aim of this study was to evaluate and ascertain the pathogenicity of different isolates of M. anisopliae on N. viridula and D. melacanthus adults under laboratory and greenhouse conditions. In the laboratory, the fungal isolates 05RA, 11RA, 08RA, and 02RA, which were collected in the field from adults of N. viridula and D. melacanthus infected with M. anisopliae, were highly pathogenic, leading to 100% mortality in adults of N. viridula and D. melacanthus at 8 days after application (DAA). However, the isolate 08RA presented higher pathogenicity in a shorter period of time for N. viridula (mean mortality time “MMT” = 2.8 days) and D. melacanthus (MMT = 4.0 days) than the remaining isolates. At the greenhouse, the isolate 08RA led to a mortality of 44.9% (N. viridula) and 35.7% (D. melacanthus) at eight DAA; however, the mortality was 100% for both species at 14 DAA, with an MMT of 8 and 10 days for N. viridula and D. melacanthus, respectively. The fungus M. anisopliae constitutes a promising alternative agent to control the growth of adult populations of N. viridula and D. melacanthus in wheat cultures.

Meloidogyne ethiopica and Meloidogyne arenaria parasitizing Oxalis corniculata in Brazil

Meloidogyne ethiopica and Meloidogyne arenaria were identified morphologically and via isozyme profiles of female nematodes extracted from Oxalis corniculata root samples collected from plantations in the municipality of Caiçara, Rio Grande do Sul State, Brazil. To the best of our knowledge, this is the first report of M. ethiopica and M. arenaria parasitizing O. corniculata in Brazil.