Metodologia de inoculação de Didymella bryoniae e retrocruzamentos visando introgressão da resistência em meloeiro rendilhado
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Data
2022-06-14
Autores
Virtuoso, Marcos Cláudio da Silva
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Universidade Estadual Paulista (Unesp)
Resumo
Dos muitos grupos de melão produzidos no Brasil, os melões nobres, como o melão rendilhado tem ganhado destaque por seu alto valor agregado e pela preferência internacional, tornando seu cultivo atrativo. A desvantagem do cultivo do melão rendilhado, é que na maioria das vezes são necessárias técnicas mais refinadas, como cultivo em casa de vegetação, principalmente, se o local de produção não oferece condições climáticas favoráveis. É o caso das regiões sul e sudeste que apresentam pouca expressão na produção de melão, porém, com o emprego da produção em casa de vegetação e o cultivo na entressafra de outras regiões, o melão pode se tornar competitivo e ser vantajoso para o produtor. O grande desafio da produção nesses locais é o aparecimento de doenças como o crestamento gomoso do caule (CGC) causado pelo fungo Didymella bryoniae, trazendo grandes prejuízos aos produtores. Pensando nisso, objetivou obter linhagens de meloeiro rendilhado resistentes ao crestamento gomoso do caule introduzindo-se genes de resistência via retrocruzamento. Para isso o trabalho foi divido em: (1) identificar a melhor condição para esporulação de D. bryoniae in vitro; (2) avaliar como diferentes condições de triagem influenciam a classificação de resistência e a ocorrência de efeitos ambientais em genótipos de meloeiro com locus de resistência monogênico dominante a D. bryoniae; (3) caracterizar e analisar a divergência genética de genótipos de meloeiro; (4) introduzir genes de resistência em linhagens elite de melão rendilhado por meio do retrocruzamento. Na primeira etapa, foram combinados diferentes espectros de luz (luz UV-A ou UV-B, luz branca e escuro contínuo) com distintos meios de cultura (BDA, V8, FM e BDAR). Em conclusão, a luz UV-B é essencial para a esporulação de D. bryoniae in vitro. Além disso, a composição do meio de cultura influencia o tipo de estrutura fúngica produzida, bem como o tamanho e a quantidade dos esporos. Nas condições de triagem, quatro experimentos em blocos casualizados foram utilizados para avaliar a reação de sete genótipos de melão, a saber, os acessos resistentes PI140471, PI420145 e PI157082, e seus respectivos cruzamentos. Esses genótipos foram inoculados por disco ou esporos de micélio-ágar e submetidos a duas condições ambientais (casa de vegetação ou ambiente controlado). Constatou-se que a seleção de genótipos de melão deve ser realizada considerando a ocorrência de interações genótipo-ambiente. Embora as condições oferecidas em casa de vegetação reflitam o ambiente natural, a avaliação e identificação de genótipos resistentes a D. bryoniae deve ser realizada em ambiente controlado com inoculação por esporos. Na etapa três, um experimento com delineamento em blocos casualizados, com quatro repetições, foi utilizado para caracterizar cinco genótipos do meloeiro, sendo eles o PI140471, PI420145, PI157082, Jab-11 e Jab-20. Durante o crescimento e desenvolvimento das plantas foi realizada a caracterização morfológica dispondo de 49 descritores. A análise resultou em três grupos distintos, obtidos pelo agrupamento hierárquico dos genótipos pelo método de UPGMA. Assim conclui-se que a caracterização e a análise de divergência genética foram eficientes para a discriminação dos grupos, demonstrando que a análise simultânea de dados qualitativos e quantitativos é viável e pode permitir maior eficiência no conhecimento da divergência entre genótipos em bancos de germoplasma. E por fim, na última etapa, foram utilizadas como parental doador duas linhagens, o PI420145 e o PI140471 contendo os genes de resistência Gsb-6 e o Gsb-1 respectivamente, para serem introduzidos cada um em uma linhagem elite (Jab-11 e Jab-20). Desta forma, foram conduzidos dois retrocruzamentos em paralelo separadamente. Foram conduzidos dois ciclos de retrocruzamento, em cada ciclo foram feitas duas etapas, sendo a primeira, a seleção das plantas para a resistência ao CGC e a segunda etapa, consistiu na avaliação das características morfoagronômicas das plantas resistentes em casa de vegetação. Com os dados fenotípicos em mãos foi feita uma análise de similaridade genética com base no algoritmo de Gower para verificar quais plantas apresentavam maior recuperação do parental recorrente para seguirem para a próxima geração. O estudo levou a seleção de plantas que são resistentes ao CGC e que apresentam maior recuperação do parental recorrente no retrocruzamento por meio do uso da análise de distância genética.
Of the many groups of melons produced in Brazil, noble melons, such as the lace melon, have gained prominence due to their high added value and international preference, making their cultivation attractive. The disadvantage of growing lace melon is that most of the time, more refined techniques are needed, such as cultivation in a greenhouse, especially if the place of production does not offer favorable climatic conditions. This is the case of the south and southeast regions, which have little expression in melon production, however, with the use of production in a greenhouse and cultivation in the off-season in other regions, melon can become competitive and be advantageous for the producer. The great challenge of production in these places is the appearance of diseases such as gummy stem blight (GSB) caused by the fungus Didymella bryoniae, causing great losses to producers. The objective was to obtain tracery melon strains resistant to gummy stem blight by introducing resistance genes via backcross. For this, the work was divided into: (1) identifying the best condition for in vitro sporulation of D. bryoniae; (2) to evaluate how different screening conditions influence the classification of resistance and the occurrence of environmental effects in melon genotypes with a dominant monogenic locus of resistance to D. bryoniae; (3) to characterize and analyze the genetic divergence of melon genotypes; (4) to introduce resistance genes into elite lines of netted melon by means of backcrossing. In the first step, different light spectra (UV-A or UV-B light, white light and continuous dark) were combined with different culture media (PDA, V8, ML and PDAB). In conclusion, UV-B light is essential for sporulation of D. bryoniae in vitro. In addition, the composition of the culture medium influences the type of fungal structure produced, as well as the size and quantity of spores. Under the screening conditions, four experiments in randomized blocks were used to evaluate the reaction of seven melon genotypes, namely, the resistant accessions PI 140471, PI 420145 and PI 157082, and their respective crosses. These genotypes were inoculated by disc or mycelium-agar spores and submitted to two environmental conditions (greenhouse or controlled environment). It was found that the selection of melon genotypes should be performed considering the occurrence of genotypeenvironment interactions. Although the conditions offered in the greenhouse reflect the natural environment, the evaluation and identification of genotypes resistant to D. bryoniae must be carried out in a controlled environment with spore inoculation. In step three, an experiment with a randomized block design, with four replications, was used to characterize five melon genotypes, namely PI140471, PI420145, PI157082, Jab-11 and Jab-20. During plant growth and development, morphological characterization was performed using 49 descriptors. The analysis resulted in three distinct groups, obtained by hierarchical grouping of genotypes using the UPGMA method. Thus, it is concluded that the characterization and analysis of genetic divergence were efficient for the discrimination of groups, demonstrating that the simultaneous analysis of qualitative vi and quantitative data is feasible and can allow greater efficiency in the knowledge of the divergence between genotypes in germplasm banks. Finally, in the last step, two strains were used as parental donors, PI420145 and PI140471 containing the resistance genes Gsb-6 and Gsb-1 respectively, to be introduced each one into an elite strain (Jab-11 and Jab-20). In this way, two backcrosses were carried out in parallel separately. Two backcrossing cycles were carried out, in each cycle two stages were carried out, the first being the selection of plants for resistance to GSB and the second stage consisting of the evaluation of the morphoagronomic characteristics of the resistant plants in a greenhouse. With the phenotypic data in hand, a genetic similarity analysis was performed based on the Gower algorithm to verify which plants showed greater recovery of the recurrent parent to move on to the next generation. The study led to the selection of plants that are resistant to GSB and that show greater recovery of the recurrent parent in backcross through the use of genetic distance analysis.
Of the many groups of melons produced in Brazil, noble melons, such as the lace melon, have gained prominence due to their high added value and international preference, making their cultivation attractive. The disadvantage of growing lace melon is that most of the time, more refined techniques are needed, such as cultivation in a greenhouse, especially if the place of production does not offer favorable climatic conditions. This is the case of the south and southeast regions, which have little expression in melon production, however, with the use of production in a greenhouse and cultivation in the off-season in other regions, melon can become competitive and be advantageous for the producer. The great challenge of production in these places is the appearance of diseases such as gummy stem blight (GSB) caused by the fungus Didymella bryoniae, causing great losses to producers. The objective was to obtain tracery melon strains resistant to gummy stem blight by introducing resistance genes via backcross. For this, the work was divided into: (1) identifying the best condition for in vitro sporulation of D. bryoniae; (2) to evaluate how different screening conditions influence the classification of resistance and the occurrence of environmental effects in melon genotypes with a dominant monogenic locus of resistance to D. bryoniae; (3) to characterize and analyze the genetic divergence of melon genotypes; (4) to introduce resistance genes into elite lines of netted melon by means of backcrossing. In the first step, different light spectra (UV-A or UV-B light, white light and continuous dark) were combined with different culture media (PDA, V8, ML and PDAB). In conclusion, UV-B light is essential for sporulation of D. bryoniae in vitro. In addition, the composition of the culture medium influences the type of fungal structure produced, as well as the size and quantity of spores. Under the screening conditions, four experiments in randomized blocks were used to evaluate the reaction of seven melon genotypes, namely, the resistant accessions PI 140471, PI 420145 and PI 157082, and their respective crosses. These genotypes were inoculated by disc or mycelium-agar spores and submitted to two environmental conditions (greenhouse or controlled environment). It was found that the selection of melon genotypes should be performed considering the occurrence of genotypeenvironment interactions. Although the conditions offered in the greenhouse reflect the natural environment, the evaluation and identification of genotypes resistant to D. bryoniae must be carried out in a controlled environment with spore inoculation. In step three, an experiment with a randomized block design, with four replications, was used to characterize five melon genotypes, namely PI140471, PI420145, PI157082, Jab-11 and Jab-20. During plant growth and development, morphological characterization was performed using 49 descriptors. The analysis resulted in three distinct groups, obtained by hierarchical grouping of genotypes using the UPGMA method. Thus, it is concluded that the characterization and analysis of genetic divergence were efficient for the discrimination of groups, demonstrating that the simultaneous analysis of qualitative vi and quantitative data is feasible and can allow greater efficiency in the knowledge of the divergence between genotypes in germplasm banks. Finally, in the last step, two strains were used as parental donors, PI420145 and PI140471 containing the resistance genes Gsb-6 and Gsb-1 respectively, to be introduced each one into an elite strain (Jab-11 and Jab-20). In this way, two backcrosses were carried out in parallel separately. Two backcrossing cycles were carried out, in each cycle two stages were carried out, the first being the selection of plants for resistance to GSB and the second stage consisting of the evaluation of the morphoagronomic characteristics of the resistant plants in a greenhouse. With the phenotypic data in hand, a genetic similarity analysis was performed based on the Gower algorithm to verify which plants showed greater recovery of the recurrent parent to move on to the next generation. The study led to the selection of plants that are resistant to GSB and that show greater recovery of the recurrent parent in backcross through the use of genetic distance analysis.
Descrição
Palavras-chave
Crestamento gomoso do caule, Caracterização, Interação GxA, Seleção, Melão, Horticultura