Phytophthora root and stem rot has developed in commercial soybean fields since 2006 in Brazil, and cultivars with resistance to this disease have not been targeted for this region. Thus, the Phytophthora sojae pathotypes are expected to have virulence to few if any of the Rps genes. The objectives of this study were to characterize the pathotype diversity of P. sojae in Brazil, determine the distribution of the pathogen and predict which Rps genes will be effective and should be used in breeding programs. Isolates were collected in six states (Rio Grande do Sul, Santa Catarina, Paraná, Mato Grosso do Sul, Minas Gerais, and Goiás). The virulence formulae were based on the response of a differential set with 14 Rps genes (1a, 1b, 1c, 1d, 1k, 2, 3a, 3b, 3c, 4, 5, 6, 7, and 8). None of the 17 pathotypes found was reported previously. The most common virulence formulas were: 1d, 2, 3c, 4, 5, 6, 7 (octal code 05471, representing 24 % of the occurrences); 1d, 2, 3b, 3c, 4, 5, 6, 7 (05671, 13 %); 1b, 1d, 2, 3a, 3c, 4, 5, 6, 7 (25571, 8 %); and 1d, 3a, 5, 7, 8 (01123, 8 %). Percentages of isolates with a susceptible interaction with each Rps gene was Rps1a (3 %), Rps1b (11 %), Rps1c (3 %), Rps1d (100 %), Rps1k (3 %), Rps2 (86 %), Rps3a (32 %), Rps3b (19 %), Rps3c (73 %), Rps4 (70 %), Rps5 (89 %), Rps6 (59 %), Rps7 (100 %), and Rps8 (22 %). There was apparently no relationship between pathotypes and origin. Stacking resistance genes Rps1a, Rps1b, Rps1c, and Rps1k with Rps3b or Rps8 would be highly effective for soybean cultivars targeted for Brazil.

Different oxidative stress parameters of four Brazilian varieties of Phaseolus vulgaris exposed to toxic O 3 concentrations were compared with the well-established bioindicator variety Pinto 111. Analysis of catalase (CAT) activity, lipoperoxidation and non-enzymatic antioxidant levels demonstrated that the varieties presented different susceptibilities to O 3 toxicity. Results indicated that Fepagro 26 and Guapo Brilhante increased the levels of lipoperoxidation in response to O 3 while catalase activity was not changed. On the opposite Iraı, Macotac¸o and Pinto 111 presented different pattern of lipoperoxidation and CAT activation indicating a relationship between CAT activation and resistance to lipoperoxidation. Analysis of the total non-enzymatic antioxidant defense levels demonstrated that although O 3 exposure decreased the non-enzymatic antioxidant defense in Iraı, lipoperoxidation levels was not enhanced in this variety as observed with Fepagro 26. Our results suggest that analysis of the oxidative stress parameters of varieties with known variations of susceptibility to O 3 may provide more precise protocols for early detection of O 3 toxicity.

Bean seedlings of Fepagro 26, Guapo Brilhante, Iraí, Macotaço and US Pinto 111 cultivars were submitted to treatments with or without addition of ozone to the ambient air, in order to evaluate the effects of exposure on photosynthesis, relative electrolyte leakage, foliar abscission and biomass of the seedlings. Exposure to ozone caused significant decreases in the net assimilation of all cultivars except Iraí. It also caused a significant increase in electrolyte leakage from the Pinto cultivar, but only when AOT 40 was the highest. It also produced significant anticipation in the time of foliar abscission in the Pinto, Fepagro and Guapo cultivars. The variability observed in the biomass measurements reflected the limitations to perform long-term controlled-environment studies, one of the major challengers yet to be overcome in order to obtain more conclusive data on damages induced on crop species resulting from tropospheric ozone enrichment.Key words: photosynthesis, relative electrolyte leakage, foliar abscission, biomass. resuMo Distúrbios fisiológicos promovidos pelo ozônio em cinco cultivares de Phaseolus vulgaris l. Plântulas de feijão das cultivares Fepagro 26, Guapo Brilhante, Iraí, Macotaço e US pinto 111 foram submetidas aos tratamentos com e sem adição de ozônio ao ar ambiente, com o objetivo de avaliar os efeitos da exposição sobre a fotossíntese, permeabilidade relativa a eletrólitos, abscisão foliar e biomassa das plântulas. A exposição ao ozônio causou decréscimos significativos na assimilação líquida de todas as cultivares, exceto na Iraí. Causou também um aumento significativo na permeabilidade relativa a eletrólitos da cultivar Pinto, mas apenas quando a AOT 40 foi a mais elevada. Além disso, produziu uma antecipação significativa no tempo de abscisão foliar nas cultivares Pinto, Fepagro e Guapo. A variabilidade observada nas medidas de biomassa total, refletiu as limitações para se executar estudos de longo prazo em condições ambientais controladas, um dos principais desafios ainda por ser superado antes que se possa obter dados mais conclusivos sobre os danos em espécies cultivadas resultantes do enriquecimento do ozônio toposférico.

The use of resistant wheat cultivars is a fundamental strategy to minimize the damages caused by blast, a disease caused by the fungus Pyricularia oryzae Triticum (PoT). The objective of this study was to evaluate (a) the reaction to blast of Brazilian wheat cultivars and (b) to determine whether there is correlation between severity of symptoms on wheat spikes and “rate of sporulation of PoT conidia on wheat spike rachis” (Rscon). Plants of 16 wheat cultivars were grown in greenhouse until flowering (Zadoks stage 65), when their spikes were inoculated with a suspension formed by mixing the conidia of three PoT isolates. The evaluated variables were blast severity on spikes at 5, 7 and 11 days after inoculation (dai) and Rscon. Rachis were evaluated individually to determine the Rscon. Correlation analyzes were carried out between blast severity means on spikes of cultivars at 5, 7 and 11 dai and the log of Rscon. The cultivars ORS Feroz, ORS Destak, CD 116, ORS 1403, ORS 1401, TBIO Aton and TBIO Mestre stood out for being classified in the statistical groups with the highest resistance to blast for the four variables considered in the study. There was a correlation between blast severity on spikes at 5, 7 and 11 dai and Rscon.