Patometria, parâmetros genéticos e reação de progênies de mamoeiro à pinta-preta

Abstract

ResumoA resistência genética constitui-se em alternativa sustentável para o controle de doenças em culturas agrícolas, sendo esta, no entanto, dependente da avaliação de populações naturais ou tradicionais visando à ampliação da base genética. Este trabalho relata a avaliação fenotípica de 24 progênies de mamoeiro, oriundas de genótipos crioulos, cultivados por pequenos agricultores no sul do Estado do Espírito Santo. Avaliaram-se características associadas à resistência à pinta-preta, importante doença desta cultura, causada pelo fungo Asperisporium caricae. Para fins comparativos, foram incluídas uma variedade resistente ('Maradol') e uma suscetível ('Golden') à pinta-preta. Pelos parâmetros genéticos estimados, concluiu-se que na população estudada há variabilidade genética quanto à resistência à pinta-preta suficiente para indicar a seleção recorrente como método de melhoramento.Palavras-chave: Asperisporium caricae, Carica papaya, herdabilidade, resistência genética, variabilidade genética. Pathometry, genetic parameters and papaya progenies reaction to black-spot disease AbstractGenetic resistance is a sustainable alternative to control diseases in crops, being indispensable the enlargement of the genetic base to introduce new resistance genes on developing cultivars. This study reports the phenotypic evaluation of 24 papaya progenies, originated of landraces cultivated for small farmers in south of the Espírito Santo State, Brazil. Characteristics related to the resistance to black-spot disease, induced by the fungi Asperisporium caricae were evaluated. For comparison one genotype resistant ('Maradol') and one susceptible ('Golden') to black-spot disease were included on the study. Based on the genetic parameters estimated, the studied population has genetic variability for resistance to black spot diseases appropriates for use of recurrent selection as crop breeding method.

Prediction of genetic gain from selection indices for disease resistance in papaya hybrids

“…Ide et al (2001) and Vivas et al (2012) reported the genotype 'Maradol' as resistant to black spot. Dianese et al (2007) reported that genotype 'Sekati' showed the lowest severity of black spot on leaves.…”

“…However, the complete resistance has not been observed in commercial genotypes of the species that have already gone through cycles of selection (Vivas et al, 2010(Vivas et al, , 2012. There is, however, the possibility of crosses generate hybrids that provide higher levels of resistance to fungal diseases.…”

Efficiency of circulant diallels via mixed models in the selection of papaya genotypes resistant to foliar fungal diseases

“…The chosen plants were analyzed for the severity of phoma spot, powdery mildew and black spot on leaves using a diagrammatic scale (Santos et al, 2011;Vivas et al, 2010Vivas et al, , 2012c. The severity of phoma spot on leaves was estimated on a leaf located below the axil of the petiole and attached to a newly opened flower.…”

“…Barreto). Because no genotype is resistant to these diseases (Dianese et al, 2007;Vivas et al, 2010Vivas et al, , 2012c, spraying with fungicides has become the primary control measure. However, pesticide residues create an obstacle for papaya export from Brazil.…”

Evaluation of new papaya hybrids

“…A feasible approach for increasing the number of commercial varieties and hybrids is to expand the genetic base of papaya by exploiting the variability existing in germplasm banks (Quintal et al, 2012;Vivas et al, 2015;Silva et al, 2017) and creating new hybrids in breeding programs (Pereira et al, 2002). Efforts should be made to broaden the genetic base and develop cultivars that meet the requirements of domestic and foreign markets and are less susceptible to pests and diseases and more resistant to biotic and abiotic stresses (Vivas et al, 2012(Vivas et al, , 2014(Vivas et al, , 2015.…”