Reação de genótipos de meloeiro ao oídio das cucurbitáceas, métodos para identificação de raças e progresso de doença
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Data
2017-01-18
Autores
Rabelo, Hudson de Oliveira [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O uso de resistência genética é considerado uma das melhores estratégias de manejo do oídio das cucurbitáceas (Podosphaera xanthii). Nesse sentido, a identificação de genótipos resistentes faz-se necessária a fim de fornecer aos programas de melhoramento novas fontes de variabilidade. Entretanto, ocorrência de raças do patógeno e a falta de padronização nos métodos de identificação têm dificultado a identificação acurada de raças do patógeno, como também a utilização de resistência genética contra o oídio das cucurbitáceas. A falta de métodos adequados tem dificultado a avaliação de incidência de oídio de modo quantitativo. O método Tripleto-Septeto visa à internacionalização da identificação de raças de oídio pelo uso de 21 linhagens diferenciadoras. O método “Area Under Disease Progress Stairs” (AUDPS) é um método essencialmente derivado do “Area Under Disease Progress Curve” (AUDPC), e ambos têm sido utilizados na avaliação de progressos de doença em outras espécies, ajudando na identificação de genes de efeito menor para resistência. O presente trabalho teve por objetivo identificar uma raça de P. xanthii em casa de vegetação, na UNESP-FCAV, bem como a reação de genótipos de meloeiro a essa raça, e identificar uma raça de oídio das cucurbitáceas em casa de vegetação, por meio do método Tripleto-Septeto, e estimar o progresso do oídio das cucurbitáceas em 21 linhagens diferenciadoras, via AUDPC e AUDPS. No primeiro experimento, foram avaliados 61 acessos de melão, duas cultivares comerciais de melão rendilhado, Louis e Fantasy, seis linhagens-elite de melão rendilhado e a cucurbitácea Benincasa hispida quanto às suas reações a uma população de oídio de ocorrência natural em casa de vegetação, em Jaboticabal-SP. Dos 61 acessos de germoplasma, sete são diferenciadoras de oídio: PI 414723, ‘PMR 45’, ‘PMR 5’, ‘WMR 29’, ‘Edisto 47’, ‘Nantais Oblong’ e ‘Védrantais’. A terceira folha verdadeira de cada planta foi inoculada, sete dias após o transplantio, com fragmentos de micélio coletados em plantas suscetíveis. A severidade da doença foi avaliada aos 42 dias após a inoculação, baseando-se em escala diagramática. O segundo experimento abordando o método Tripleto-Septeto e progressos de doenças foi conduzido em uma casa de vegetação com uma população de oídio de ocorrência natural, em Salinas, Califórnia. A severidade de oídio foi avaliada nas 21 diferenciadoras, aos 15, 22, 32 e 41 dias após a inoculação (DAI), com base em escala diagramática. A identificação da raça considerou somente a última avaliação, enquanto AUDPC e AUDPS, além de suas padronizações, consideraram as quatro avaliações. Foi identificada a raça 4 de P. xanthii em meloeiro, no estado de São Paulo, pela primeira vez. Os genótipos A19, A32, Solarking, PI 124111, PI 414723, A30, JAB-11, JAB-20, JAB-3, B. hispida, JAB-7, C384, C67, ‘Edisto 47’, ‘PMR 5’, JAB-9 e JAB-18 foram resistentes à raça 4 de P. xanthii. A diferenciadora ‘Nantais Oblong’ é suscetível à raça 4 de P. xanthii. Foi identificada a raça anteriormente denominada S, agora designada como 127.127.126 pelo Tripleto-Septeto. AUDPS identificou maiores índices de doença que AUDPC, bem como seus resultados corroboraram aqueles obtidos pelo método convencional de identificação. AUDPS pode ser utilizada para avaliação de progresso de doença do oídio das cucurbitáceas.
Genetic resistance is considered one of the most suitable strategies to control cucurbit powdery mildew (CPM) incited by (Podosphaera xanthii). Accordantly, the identification of resistant genotypes is necessary to provide to breeding programs new sources of variability. However, the occurrence of races, and the lack of standardization of methods of identification have been hampered the use of genetic resistance against cucurbit powdery mildew. The lack of suitable methods has made difficult the assessment of CPM in quantitative ways. The method Triplet-Septet aims the internationalization of CPM identifications by using a set of 21 differentials. The method Area Under Disease Progress Stairs (AUDPS) is essentially derived from Area Under Disease Progress Curve (AUDPC), and both have been used to evaluate disease progresses on other crops, helping to identify minor genes for resistance. This thesis aimed to identify a P. xanthii race in a greenhouse at the UNESP-FCAV, as well the reaction of melon genotypes to that race; to identify a new cucurbit race in greenhouse via Triplet-Septet method; and to estimate the CPM disease progress on 21 race differentials, via AUDPC and AUDPS. The first experiment evaluated 61 melon germplasm accessions, two net melon cultivars (‘Louis’ and ‘Fantasy’), six net melon elite-inbred lines, and the winter melon (Benincasa hispida) regarding their reactions to a CPM population, naturally occurring in a greenhouse, in Jaboticabal, SP. Seven of the 61 germplasm accessions are known as CPM race differentials: PI 414723, ‘PMR 45’, ‘PMR 5’, ‘WMR 29’, ‘Edisto 47’, ‘Nantais Oblong’ and ‘Védrantais’. The third true leaf of each plant was inoculated with fragments of mycelia at seven-days after transplanting and evaluated 42-days after inoculation, based on visual scale. The second experiment, about the Triplet-Septet method and progress disease, was carried out in a greenhouse naturally infected with a CPM population, in Salinas, CA. Severity of CPM was measured on 21 differentials at 15, 22, 32, and 41 days after inoculation (DAI), based on a visual scale. Race identification was based on the final evaluation, whereas AUDPC and AUDPS, and their standardizations were based on all four evaluations. Podosphaera xanthii race 4 was identified for the first time in São Paulo state, Brazil. Genotypes A19, A32, ‘Solarking’, PI 124111, A30, JAB-11, JAB-20, JAB-3, winter melon, JAB-7, C384, C67, JAB-9, and JAB-18 were resistant to CPM race 4. The differential ‘Nantais Oblong’ is susceptible to race 4. Race S was identified based on the current race differentials, now designated as 127.127.126 by the Triplet-Septet method. AUDPS identified higher levels of disease than AUDPC, and its results agreed with those obtained by conventional race identification methods (current and Triplet-Septet). AUDPS can be used to evaluate the disease progress of cucurbit powdery mildew.
Genetic resistance is considered one of the most suitable strategies to control cucurbit powdery mildew (CPM) incited by (Podosphaera xanthii). Accordantly, the identification of resistant genotypes is necessary to provide to breeding programs new sources of variability. However, the occurrence of races, and the lack of standardization of methods of identification have been hampered the use of genetic resistance against cucurbit powdery mildew. The lack of suitable methods has made difficult the assessment of CPM in quantitative ways. The method Triplet-Septet aims the internationalization of CPM identifications by using a set of 21 differentials. The method Area Under Disease Progress Stairs (AUDPS) is essentially derived from Area Under Disease Progress Curve (AUDPC), and both have been used to evaluate disease progresses on other crops, helping to identify minor genes for resistance. This thesis aimed to identify a P. xanthii race in a greenhouse at the UNESP-FCAV, as well the reaction of melon genotypes to that race; to identify a new cucurbit race in greenhouse via Triplet-Septet method; and to estimate the CPM disease progress on 21 race differentials, via AUDPC and AUDPS. The first experiment evaluated 61 melon germplasm accessions, two net melon cultivars (‘Louis’ and ‘Fantasy’), six net melon elite-inbred lines, and the winter melon (Benincasa hispida) regarding their reactions to a CPM population, naturally occurring in a greenhouse, in Jaboticabal, SP. Seven of the 61 germplasm accessions are known as CPM race differentials: PI 414723, ‘PMR 45’, ‘PMR 5’, ‘WMR 29’, ‘Edisto 47’, ‘Nantais Oblong’ and ‘Védrantais’. The third true leaf of each plant was inoculated with fragments of mycelia at seven-days after transplanting and evaluated 42-days after inoculation, based on visual scale. The second experiment, about the Triplet-Septet method and progress disease, was carried out in a greenhouse naturally infected with a CPM population, in Salinas, CA. Severity of CPM was measured on 21 differentials at 15, 22, 32, and 41 days after inoculation (DAI), based on a visual scale. Race identification was based on the final evaluation, whereas AUDPC and AUDPS, and their standardizations were based on all four evaluations. Podosphaera xanthii race 4 was identified for the first time in São Paulo state, Brazil. Genotypes A19, A32, ‘Solarking’, PI 124111, A30, JAB-11, JAB-20, JAB-3, winter melon, JAB-7, C384, C67, JAB-9, and JAB-18 were resistant to CPM race 4. The differential ‘Nantais Oblong’ is susceptible to race 4. Race S was identified based on the current race differentials, now designated as 127.127.126 by the Triplet-Septet method. AUDPS identified higher levels of disease than AUDPC, and its results agreed with those obtained by conventional race identification methods (current and Triplet-Septet). AUDPS can be used to evaluate the disease progress of cucurbit powdery mildew.
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Palavras-chave
AUDPC, AUDPS, Cucumis melo L., Raças fisiológicas, Resistência genética, Podosphaera xanthii, Genetic resistance, Physiological races