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El complejo mancha de asfalto (CMA) del maíz (Zea mays L.), inducido por los hongos Phyllachora maydis Maubl., y Monographella maydis Müller & Samuels, es una enfermedad de importancia económica, debido a que provoca severas pérdidas en el rendimiento y deteriora la calidad del forraje. El mejoramiento genético de la resistencia del hospedante a través de la generación de genotipos resistentes representa la medida de control más eficiente para la enfermedad. Se conoce poco respecto a la base genética de la resistencia al CMA, por lo cual se determinaron las aptitudes combinatoria general (ACG) y específica (ACE) de 18 líneas endogámicas S7 mediante el Modelo I de frecuencias fijas de Griffing, bajo el Método II que incluyó las 18 líneas más sus 153 cruzas directas posibles. El diseño experimental fue bloques completos al azar, en 4 ambientes diferentes ubicados en los Estados de Veracruz, Guerrero, Puebla y Oaxaca. Tanto la ACG como la ACE tuvieron efecto significativo (P < 0.01), por lo que, tanto los efectos génicos de dominancia como los de aditividad son importantes en la resistencia a la enfermedad. Sin embargo, la ACG fue 45 veces más grande que la ACE, de modo que los efectos génicos aditivos son más importantes, por lo que diversos genes no alelicos están involucrados en resistencia al CMA en maíz, por lo tanto es posible acumular diversos genes en un solo genotipo mediante métodos de mejoramiento genético. Los híbridos más resistentes fueron los derivados de dos líneas con ACG y ACE negativa. Las mejores líneas para producir híbridos altamente resistentes fueron CML-329, CLRCW-105-B y [M37W/ZM607]. La selección recurrente podría ser el método de mejoramiento más útil para acumular e incrementar los niveles de resistencia a la enfermedad en poblaciones sintéticas o compuestas. Los efectos de dominancia fueron los más importantes en algunas cruzas específicas.
Tar spot complex (TSC) of maize (Zea mays L.), caused by the fungi Phyllachora maydis Maubl, and Monographella maydis Müller & Samuels, is a disease of economic importance, as it causes severe losses in yield and forage quality. Genetic improvement of host resistance through the generation of resistant genotypes is the most efficient strategy for managing disease. Little is known about the genetic basis of maize resistance to TSC, therefore general combining ability (GCA) and specific combining ability (SCA) of 18 inbred lines S7 was determined by the Model I of fixed frequency defined by Griffing, under Method II which included 18 lines plus all its 153 possible single crosses. The experimental was laid out as a randomized complete block design and conducted in 4 different environments in the States of Veracruz, Guerrero, Puebla and Oaxaca. Both GCA and SCA were significant (P < 0.01), indicating that both additive and dominant gene effects are important in determining resistance to TSC. However, the GCA was 45 times larger than the SCA, indicating that additive gene effects are most important in TSC resistance and that different non-allelic genes may be involved in conditioning resistance to TSC in maize. It is therefore possible to pyramid or stack different resistance genes in the same background by breeding methods. The most resistant hybrids were derived from two lines with high negative GCA and SCA. The best lines to produce highly resistant hybrids were CML-329, CLRCW-105-B and [M37W/ZM607], which had the best negative GCA effects. Recurrent selection may be the most useful method of improving to accumulate and increase levels of TSC resistance in synthetic or composite populations. Dominance effects were the most important in some crosses.
Tar spot complex (TSC) of maize (Zea mays L.), caused by the fungi Phyllachora maydis Maubl, and Monographella maydis Müller & Samuels, is a disease of economic importance, as it causes severe losses in yield and forage quality. Genetic improvement of host resistance through the generation of resistant genotypes is the most efficient strategy for managing disease. Little is known about the genetic basis of maize resistance to TSC, therefore general combining ability (GCA) and specific combining ability (SCA) of 18 inbred lines S7 was determined by the Model I of fixed frequency defined by Griffing, under Method II which included 18 lines plus all its 153 possible single crosses. The experimental was laid out as a randomized complete block design and conducted in 4 different environments in the States of Veracruz, Guerrero, Puebla and Oaxaca. Both GCA and SCA were significant (P < 0.01), indicating that both additive and dominant gene effects are important in determining resistance to TSC. However, the GCA was 45 times larger than the SCA, indicating that additive gene effects are most important in TSC resistance and that different non-allelic genes may be involved in conditioning resistance to TSC in maize. It is therefore possible to pyramid or stack different resistance genes in the same background by breeding methods. The most resistant hybrids were derived from two lines with high negative GCA and SCA. The best lines to produce highly resistant hybrids were CML-329, CLRCW-105-B and [M37W/ZM607], which had the best negative GCA effects. Recurrent selection may be the most useful method of improving to accumulate and increase levels of TSC resistance in synthetic or composite populations. Dominance effects were the most important in some crosses.
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Journal
Revista Fitotecnia Mexicana
Journal volume
38
Journal issue
1
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Place of Publication
Mexico
Publisher
Sociedad Mexicana de Fitogenetica