Selection for papaya resistance to multiple diseases in a base population of recurrent selection

Abstract

Selection for papaya resistance to multiple diseases in a base population of recurrent selectionABSTRACT: Papaya has a narrow genetic base concerning disease resistance, with few genetically distinct cultivars for planting in the world. Losses in crop production caused by fungal and viral diseases, added to the absence of resistant cultivars available to producers, have reduced the competitiveness of crops. Therefore, this study aimed to estimate the direct and combined genetic gains in the base population of the recurrent papaya selection and to indicate promising individuals for resistance to phoma spot and black spot. The population used in this study originated from the crossing of dioecious, female individuals and holders of a gene pool for resistance to phoma spot and black spot.These were crossed with elite individuals with a gene pool for production traits and fruit quality. The experiment was carried out without an experimental design, containing one plant per plot. Three measurements were taken on 255 individuals for five traits of disease resistance, being: four associated with black spot (incidence and severity on the leaf and fruit) and one associated with phoma spot (severity on the leaf). With the observations obtained, the REML/BLUP procedure was performed to estimate the temporary and permanent environmental effects. Such values were used to know the genetic parameters of the population and to elaborate a combined selection index, as well as to compare the gains with the direct selection. The results indicate low repeatability for the traits and that the gains obtained from the use of the combined selection index better rank the genotypes in comparison to the gains obtained by direct selection.

Influence of Weather Parameters on Incidence of Black Spot of Papaya Caused by Asperisporium caricae

“…This disease was first observed in the variety "Honey dew" at Chettali, Karnataka later it was observed in variety CO 1 in Palani hills, Tamil Nadu during cooler months was reported by Ullasa et al [4]. The symptoms appear on the upper surface of leaves as small water-soaked spots, later these spots become greyish white in colour and the corresponding lower surface of the leaves develop black velvety conidial mass around the lesions [5]. Severely affected leaves shrivel, develop larger necrotic lesions which become brittle and finally die.…”