Inheritance of resistance to dieback disease in mango (Mangifera indica)

Abstract

The fungi 'Lasiodiplodia theobromae' and 'Neofusicoccum parvum' are pathogens responsible for causing dieback disease in mangoes. Studies on the inheritance of resistance to these fungal diseases in mango are quite limited. The objective of the present study was to evaluate the inheritance of resistance to dieback disease in three pseudo-F2 progenies to assist in mango breeding programs. Young branches containing young leaves were selected, and suspension of 103 conidia/mL of 'L. theobromae' or 'N. parvum' was sprayed separately. After inoculation, leaves were protected in a plastic wet chamber for 48 hours. The infection was estimated by taking the branches without symptoms/total number of inoculated branches. Plants without disease symptoms in more than 90% of the branches, in three different inoculation periods, were considered as resistant. Keitt, Haden, and Espada cultivars were resistant to both fungi, while 'Tommy Atkins' was susceptible to both pathogens. Monogenic resistance, conferred by recessive alleles, was observed for 'L. theobromae' for the three crossings evaluated, despite the 13:3 segregation detected for 'Keitt' x 'Tommy Atkins'. For 'N. parvum', recessive resistance with 3:1 monogenic segregation was observed in the crossing 'Keitt' x 'Tommy Atkins', and 9:7 epistatic segregation was reported in the crossing 'Haden' x 'Tommy Atkins' and 'Espada x 'Tommy Atkins'. The mono or digenic inheritance observed in the present study indicates the possibility of selection in the F2 generation and identification of plants with double resistance to 'L. theobromae' and 'N. parvum' in mango trees.