Inheritance of resistance to powdery mildew in the watermelon and development of a molecular marker for selecting resistant plants

Abstract

The race of watermelon powdery mildew (PM) present in South Korea was confirmed, and genetic inheritance of resistance to this race was determined from a cultivars 'Arka Manik'. Bioassay tested on a set of melon differential genotypes indicated that the race of P. xathii predominating in South Korea was either belonged to race 1W or another race different from race 2W. Inheritance of PM resistance was studied from F-2, F-2:3, and reciprocal backcross generations derived from 'Arka Manik' (resistant cultivar) x HS3355 (susceptible line). The segregation ratios indicated that resistance to PM in 'Arka Manik' is conditioned by a single incompletely dominant gene (Pm1.1). Bulked segregant analysis (BSA) of F2 plants using random amplification of polymorphic DNA (RAPD) identified one polymorphic polymerase chain reaction (PCR) band (OP-R483) and a close linkage (3.6 cM) was observed between resistance and OP-483. The marker OP-483 was converted to cleaved amplified polymorphic sequence (CAPS-G/C) and a single nucleotide polymorphism (SNP) marker (MCA-A/G) using melting curve analysis. MCA-A/G marker genotyping of a wide range of susceptible breeding lines revealed that the marker allele of 'Arka Manik' was unique in breeding populations.