Inheritance of resistance to systemic symptom expression of Melon necrotic spot virus (MNSV) in Cucumis melo L. `Doublon'

In melon (Cucumis melo L.) a resistance mechanism to Melon necrotic spot virus (MNSV) controlled by a single recessive gene called nsv has been reported. We found that following mechanical inoculation of the virus C. melo cv. ‘Doublon’ shows only local reaction, but it does not develop any systemic symptom and the virus only can be recovered from the local lesions. This reaction could be considered as a new source of resistance to MNSV. In this work,the genetic control of this behaviour in the progenies from the cross ‘Doublon’ × ‘ANC-42’ (a susceptible line) is studied. We report two complete dominant genes, which we propose to call Melon necrotic resistance 1 (Mnr1) andMelon necrotic resistance 2 (Mnr2), controlling this character. The genetic linkage between one of these genes and nsv in the populations derived from the cross between ‘Doublon’ and ‘PMR-5’ (a resistant line) is also reported. The map distance between these two loci was estimated to be 19 cm. This revised version was published online in July 2006 with corrections to the Cover Date.