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Foram realizadas comparacões morfológicas auxanográficas e patogênicas entre Colletotrichum gossypii e Colletotrichum gossypii var. Cephalosporioides. No aspecto morfológico foram estudados: o número de núcleos nos conídios, a morfologia de apressórios e o tamanho dos conídios. Quanto à auxanográfia foram estudados os requerimentos nutricionais. A patogenicidade foi avaliada em maçãs destacadas e em plântulas de dois cultivares de algodoeiro: Nu-15 (suscetível a ramulose) e IAC-17 (mais resistente a ramulose), através da inoculação dos fungos. Ambos fungos apresentam conídios uninucleados e apressórios morfologicamente semelhantes. Quanto ao tamanho de conídios os fungos são diferentes. O agente da ramulose pode apresentar conídios de comprimento maior que 16 µm enquanto que todos os conídios do agente da antracnose são menores que 16 µm. Também auxanograficamente os dois fungos são diferentes: o colletotrichum causador da ramulose e deficiente em asparagina ou ácido aspártico, enquanto que o causador da antracnose e auxoautotrófico para fatores de crescimento. Quanto a patogenicidade em maçãs destacadas de IAC-17 e em plântulas de Nu-15 e IAC-17 os fungos comportaram-se de maneira semelhante. Em maçãs destacadas do cultivar Nu-15 o fungo causador da antracnose foi mais patogênico que o causador da ramuloseComparaisons among Colletotrichum gossypii and Colletotrichum gossypii var. cephalosporioides cultures in the morphological, auxanographic and pathogenic aspects were perfomed. The number of nuclei in the conidia, the morphology of the apressoria and the size of the conidia were evaluated in the morphological aspect. Nutritional requirements were studied in the auxanographic aspect. The pathogenicity was evaluated on detached bolls and seedlings of two cultivars of cotton plant: Nu-15 and IAC-17. Conidia of both fungi are uninucleated and the morphology of their appressoria is similar. Regarding the size of the conidia the fungi are different. The fungus responsible for the ramulosis can have conidia with a lenght larger than 16 µm while all the others conidia from the agent that produces anthracnosis are smoller than 16 µm. Auxanographically the two fungi are also different: The fungus responsible for the ramulosis is deficient in asparagin or aspartic acid, while the responsible for the anthracnosis is auxoautotrophic for gowth factors. The fungi were similar in pathogenicity in detached bolls of the IAC-17 and seedlings of Nu-15 and IAC-17 of cotton. The fungi were different in pathogenecity in detached bolls of Nu-15. The fungus responsible for the anthracnosis was more pathogenic than the responsible for the ramulosis in this cultiva

Diallel crosses among maize lines with emphasis on resistance to foliar diseases

Ten elite maize (Zea mays L.) lines were crossed in a complete diallel scheme and the single-cross hybrids obtained were assessed at four experimental stations of the Agronomic Institute of Campinas, in São Paulo State, Brazil. The experiments were set up in a randomized complete block design with three replications, including four commercial checks. The experimental plots consisted of two 5-m rows spaced at 0.9 m, with a total of 50 plants. The traits assessed included: days to mid-tassel pollen shed (DPS), plant height (PH), ear height (EH), grain yield, corrected for a 50-plant stand and 14% moisture (GY corr.), and resistance to Phaeosphaeria maydis and Puccinia polysora. General and specific combining ability effects (GCA and SCA) were determined. There was extensive genetic variability among hybrids with the best hybrids (HS 04 x 10 and HS 10 x 11) not differing from the commercial checks. The lines with the greatest potential for hybrid synthesis included: L 10, L 11 and L 13, because they had higher GCA for yield, moderate resistance to P. maydis and reduced EH. The greatest contribution to reduction of the Phaeosphaeria stain was obtained with L 5. The magnitude of the GCA relative to the total variation indicated that additive effects predominated for resistance to P. maydis and P. polysora. Significant SCA (P < 0.01) was also found, indicating dominance effects as well

Maize cultivars reaction to Phaeosphaeria leaf spot in São Paulo State, Brazil

Trinta cultivares de milho foram avaliadas quanto à severidade da mancha de Phaeosphaeria, em três locais do Estado de São Paulo, em condições de infecção natural. O delineamento experimental utilizado foi o de blocos ao acaso, com três repetições. Foram avaliadas dez plantas por parcela, 90 a 100 dias após o plantio. Foi utilizada uma escala de notas de 1 a 9, correspondendo às porcentagens de área foliar afetada de 0 e >75%, respectivamente. Em Campinas e Capão Bonito houve baixa intensidade da doença (notas de 1,0 a 3,0), e em Vargem Grande do Sul foi observada alta severidade de Phaeosphaeria, com notas variando de 2,0 a 6,0. A partir dos resultados de Vargem Grande do Sul, foram consideradas resistentes (com nota ≤ 3,0): CO 42, IAC Taiúba, P 3041, AGM 2007, C 805, P 3051, C 425, Dina 70, C 701, Dina 170 e XL 380, e mais suscetíveis (notas 6,0): G 85 e AG 612. O coeficiente de correlação linear entre notas e peso de grãos apresentou valores altos, negativos e significativos, mostrando que de maneira geral a mancha de Phaeosphaeria afetou negativamente a produção das cultivares estudadas. Os valores de temperatura e precipitação durante o ciclo da cultura indicaram que a uniformidade de precipitação foi o fator preponderante no desenvolvimento da doença.Thirty maize cultivars were evaluated for Phaeospharia leaf spot severity, in three locations in the State of São Paulo, under natural infection. The experiment included three replications of a randomized block design. Ten plants per plot were evaluated from 90 to 100 days after sowing through a scale of notes varying from 1 to 9, being 1 for 0% and 9 for more than 75% foliar area affected. In Campinas and Capão Bonito there was low disease severity (notes from 1 to 3), while in Vargem Grande do Sul high severity of Phaeosphaeria was observed, with notes from 2.0 to 6.0. From the results of Vargem Grande do Sul, SP, CO 42, IAC Taiúba, P 3041, AGM 2007, C 805, P 3051, C 425, Dina 70, C 701, Dina 170 and XL 380 were considered resistant (notes ≤ 3.0), and G 85 and AG 612 more susceptible (note 6.0). The linear correlation coefficient among notes and grain weight presented high values, negative and significant, showing that generally the Phaeosphaeria leaf spot negatively affected the yield of the evaluated cultivars. The values of temperatures and precipitation during the culture cicle indicated that the uniformity of precipitation was the most important factor in the disease development