Rvi4 and Rvi15 are the same apple scab resistance genes

Abstract

The apple (Malus x domestica) scab (Venturia inaequalis) resistance genes Rvi4 and Rvi15 were mapped to a similar region on the top of linkage group 2 and both resistance genes elicit the same type of resistance reaction, i.e., a hypersensitive response; hence, it is suspected that the two genes may be the same. As the two resistance genes Rvi4 and Rvi15 are currently used in apple breeding, it is important to clarify whether the two resistance genes are the same or not. Several approaches were used to make this determination. First, the pedigree of the genotype GMAL 2473, the source of Rvi15, was reconstructed. GMAL 2473 was found to be an F1 of ‘Russian seedling’, the genotype, which is known to also be the source of Rvi4. Next, it was further demonstrated that ‘Regia’, a cultivar known to carry Rvi4 (and Rvi2), carries the same gene (Vr2-C), which was demonstrated to be the gene inducing Rvi15 resistance. Finally, it was shown that transgenic lines carrying Vr2-C are compatible with race 4 apple scab isolates. Taken all together, these results definitively demonstrate that Rvi4 and Rvi15 are the same resistance gene. For future studies, we suggest referring to this resistance with the first name that was assigned to this gene, namely Rvi4.

Screening of Apple Cultivars for Scab Resistance in Kazakhstan

“…To identify carriers of the Rvi2 + Rvi8 gene, PCR analysis of apple genotypes was carried out using the SCAR marker OPL19 (Table 6), which had an expected PCR product size of 433 bp. The presence of the OPL19-SCAR marker in the genomes of the cultivars 'Prima' and 'Modi' was previously confirmed by other researchers [21,22,49,50]. We showed that 24 apple cultivars are carriers of this gene: 'Ainur', 'Aigul', 'Kamila', 'Diana', 'Saltanat', 'Korey', 'Mutsu', 'Landsberger Renette', 'Star Crimson', 'Stark's Earliest', 'Talgarskoye', 'Williams Pride', 'Gala', 'Idared', 'Pink Lady', 'Braeburn', 'Jeromine', 'SuperChief', SQ159 (Natyra), 'Fuji', 'Pinova', 'Modi', 'Voskhod', and 'Prima'.…”

“…Two closely associated markers were identified: CH02c02a and CH02f06 [36,47]. This is the most promising resistance gene that can be incorporated relatively quickly into a new cultivar in combination with other scab resistance genes for durable resistance [49]. It should be noted that depending on the parent forms, some seedlings that do not carry known resistance genes may be resistant to the pathogen due to the presence of other genetic determinants of resistance.…”

A non‐invasive method for phenotyping scab‐tolerant apple plants using volatile organic compounds

“…Several other scab-resistant genes (Rvi1 to Rvi17) have been isolated and mapped from apple cultivars around the world (Bus et al, 2011). So far, only the Rvi4, Rvi11, and Rvi15 genes have been proven to provide durable scab resistance (Peil et al, 2023).…”

“…Various apple breeding programs are underway around the world to develop apple cultivars that are resistant to scab and have good aesthetic qualities as well (Höfer et al, 2021). As of now, genebased detection is mainly used to assess a new breeding line's ability to resist scab disease (Peil et al, 2023). The problem with genebased detection is that it is time-consuming and destructive.…”