Abstract The present study aimed to investigate the response of soybean cultivars with different susceptibility levels to the root-knot nematode Meloidogyne javanica at varied time intervals by analyzing the initial plant–nematode interaction using antioxidant enzymes as oxidative stress markers. A 4 × 4 × 2 factorial method with 5 repetitions was used to analyze 4 soybean cultivars at 4 different collection times—6, 12, 24, and 48 h—with and without M. javanica inoculation. The parameters evaluated were the activities of antioxidant enzymes phenol peroxidase (POX) and ascorbate peroxidase (APX); the concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA); and the number of M. javanica juveniles penetrated into each plant. H2O2 concentration varied among the cultivars with and without inoculation and at different collection times as indicated by MDA concentration and POX and APX activities, demonstrating a rapid response of the host to an infection by M. javanica. Oxidative stress caused by M. javanica did not vary among the soybean cultivars regardless of their susceptibility level; however, the antioxidant enzymes POX and APX responded according to the susceptibility level of the cultivars. rootknot root knot plantnematode plant markers times6, times6 6, 6 times—6 12 24 hwith h M (POX (APX) HO H O (H2O2 (MDA) H2O however times— 1 (APX (H2O (MDA

No período de março de 2004 a janeiro de 2005 foi avaliada a resistência de 48 cultivares comerciais de soja a Colletotrichum truncatum. Plântulas de soja foram inoculadas no estádio V1/V2 e, após as inoculações, foram mantidas em casa de vegetação, sob condições de umidade relativa do ar acima de 95%, durante 10 dias. Após esse período, as plântulas foram avaliadas para determinar a reação das cultivares. A severidade dos sintomas foi obtida pela avaliação das lesões nas folhas, determinando-se os graus de resistência das plântulas através de uma escala de notas de severidade, com valores de 1 a 9. Somente as cultivares Tabarana, Cometa e EMGOPA 316 foram suscetíveis a Colletotrichum truncatum.

During the period between March, 2004 and January 2005, the reaction of 48 commercial cultivars of soybean to Colletotrichum truncatum was evaluated in the greenhouse facilities of the Universidade Federal de Santa Maria. The seedlings were inoculated in the stadium V1/V2 . After inoculation, plants were kept in the greenhouse under a relative humidity of 95% for 10 days, before evaluation. After that period, the seedlings were evaluated to determine the reaction of cultivars. Seedlings were evaluated for disease reaction according to a scale with values from 1 to 9. Only the cultivars Tabarana, Cometa and Emgopa 316 showed to be susceptible to Colletotrichum truncatum.

Nos anos de 2003 e 2004, na Universidade Federal de Santa Maria, foram avaliados 60 genótipos de Feijoeiro Comum (Phaseolus vulgaris), de origem andina e meso-americana, com o objetivo de caracterizar sua estrutura genética quanto à resistência a 12 raças fisiológicas de Colletotrichum lindemuthianum, no estádio juvenil (V1/V2). As reações de cada genótipo foram avaliadas com base em uma escala de notas com valores de 1 a 9 a partir das quais foram calculados dois índices de resistência para cada genótipo avaliado e um índice de virulência para cada raça inoculada. A análise fenética dos dados de virulência foi obtida a partir da construção de uma matriz, considerando as reações incompatíveis e compatíveis. Maior variabilidade genética em relação à resistência a Colletotrichum lindemuthianum foi observada no germoplasma Andino do que aquela apresentada pelo germoplasma Meso-americano. Níveis de resistência que podem não ser do tipo raça-específica também foram observados.

Sixty genotypes of common bean (Phaseolus vulgaris) from the Meso-American and Andean gene pool were evaluated in 2003 and 2004 at Universidade Federal de Santa Maria, State of Rio Grande do Sul, Brazil. Host genetic structure was evaluated based on the reaction of the sixty genotypes, in the juvenile state (V1/V2) to 12 physiological races of Colletotrichum lindemuthianum. The phenetic analysis was generated from virulence data considering incompatible and compatible reactions. Lower resistance index was observed. However, complex resistance was found in some genotypes. Higher genetic variability for resistance to Colletotrichum lindemuthianum was observed in the Andean than the Meso-American germplasm.