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Master's Dissertation
DOI
https://doi.org/10.11606/D.11.1995.tde-20220208-011230
Document
Author
Full name
Paulo Sergio Koch
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 1995
Supervisor
Title in Portuguese
Análise genética de um cruzamento dialélico em abobrinha (Cucurbita pepo L.)
Keywords in Portuguese
ABOBRINHA
ANÁLISE GENÉTICA
CRUZAMENTO DIALÉLICO
Abstract in Portuguese
O presente trabalho teve como objetivos obter estimativas de heterose, coeficientes de correlação e capacidade de combinação para caracteres de produção, através de um sistema de cruzamento dialélico completo sem recíprocos 7 x 7. Utilizaram-se sete linhagens parentais endogâmicas extraídas a partir de um único cruzamento biparental. Obtiveram-se os 21 híbridos F1 possíveis entre elas. Os 29 tratamentos, constituídos pelos 7 parentais, 21 híbridos e o híbrido original, foram testados no delineamento em blocos atualizados completos, com 4 repetições e 7 plantas por parcela, na Estação Experimental de Bragança Paulista, da Agroflora S/A, localizada em Bragança Paulista, SP. Foram avaliados os caracteres: número de flores femininas por planta até o 31º nó (NFF); número de frutos por planta em colheita precoce (NFP) e em colheita total (NFT). Realizaram-se 22 colheitas, sendo consideradas como colheita precoce as primeiras 11 colheitas. Os frutos foram colhidos no ponto comercial para o mercado de São Paulo com peso de fruto em torno de 200-250 g. As análises estatístico-genéticas foram procedidas segundo a metodologia de análise dialélica de GRIFFING (método 2, modelo misto B). As correlações entre caracteres foram medidas pelo coeficiente de PEARSON. As heteroses foram calculadas em relação à média dos parentais (Hmp), ao parental superior (Hps) e ao híbrido original (Hcp). Obtiveram-se 2 linhagens parentais e 6 híbridos F1 superiores ao híbrido original, para os três caracteres avaliados. Verificaram-se expressivos valores positivos de heterose para produção total e produção precoce nas combinações híbridas, ao passo que para o caráter número de flores femininas, os valores dos híbridos não diferiram dos parentais. Há predominância de efeitos gênicos aditivos (CGC) na expressão dos caracteres estudados. O coeficiente de correlação entre número de flores femininas e produção foi bastante alto (r = 0,8). Selecionaram-se os híbridos P1 x P2 (padrão cilíndrico) e P2 x P5 (padrão bojudo), como potencialmente competitivos, sob o ponto de vista comercial.
Title in English
Genetic analysis of a diallel cross in summer squash (Cucurbita pepo L.)
Abstract in English
The objectíves of the present work were to obtain estimates of heterosis, correlations and combining ability for yield traits, in a seven-parent partial diallel crosssystem. Seven inbred lines were obtained from an original biparental cross. Crosses were made in alI possible combinations to obtain 21 F1 hybrids, except the reciprocals. Twentynine entries (7 parents, 21 F1 hybrids and the original hybrid) were grown in a randomized complete block design with four replications, 7 plants per plot, at Bragança Paulista Research Station, Agroflora S/A, in Bragança Paulista, SP, Brazil, in 1993. The following traits were evaluated: number of female flowers per plant (NFF); number of fruits per plant in early harvest (NFP) and in total harvest (NFT). Twenty two harvests were made and the first 11 of them were considered early harvest. Fruits were harvested at marketable size (200 - 250 g/fruit). The data for each trait were first subjected to the analysis of variance. GRIFFINGs method 2, mixed model B was then used to estimate the general (CGA) and specific combining abilities (SCA). Correlations were measured using PEARSONS coefficient. Heterosis were described as midparent heterosis (Hmp), high parente heterosis (Hps) and relative check performance (Hcp).Two parental lines and six F1 hybrids were superior to the original F1 hybrid for all traits that were evaluated. Heterotic effects were positive for NFP and NFT in the hybrid combinations. On the other hand, number of female flowers per plant did not differ among the genotypes.The additive gene effects were more important than non-additive gene effects for all traits that were evaluated. PEARSONs coefficiente between number of female flowers and yield was high (r = 0,8). The hybrids P1 x P2 (cilindric fruit shape) and P2 x P5 (conic fruit shape) were selected as pontencially competitive in the market.
 
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