Resistance sources to Valsa canker (Valsa ceratosperma) in a germplasm collection of diverse Malus species

Abstract

Although Valsa canker caused by Valsa ceratosperma (Tode ex Fr.) Maire is one of the most destructive diseases in apple (Malus · domestica Borkh.) especially in eastern Asia, information available to help with breeding against Valsa canker in apples is limited. In this work, 53 accessions of diverse Malus species and their interspecific hybrids were tested for resistance to V. ceratosperma, using an excised shoot assay. Dormant shoots and succulent growing shoots from each accession were inoculated with a virulent isolate AVC-12 of V. ceratosperma, and the length of necrosis was measured at 10 days post-inoculation for the dormant shoots and at 7 days post-inoculation for the growing shoots. The lesion length relative to the susceptible control ÔFuji' in dormant shoots (RL D ) and to that in growing shoots (RL G ) were simple but useful parameters to differentiate between resistant and susceptible accessions. Fourteen accessions from M. baccata, M. florentina, M. halliana, M. micromalus, M. pratii, M. sieboldii, M. yunnanensis, M. · floribunda and M. · platycarpa gave low RL D and RL G values of less than 0.6 and were evaluated as resistant regardless of the difference in the stage of growth. The highest level of resistance was found in M. sieboldii. This high level of resistance in M. sieboldii was effective against different isolates of V. ceratosperma.

Gα proteins Gvm2 and Gvm3 regulate vegetative growth, asexual development, and pathogenicityon apple in Valsa mali

“…Since the pathogen penetrates extensively into the host phloem and xylem [25], chemical treatment cannot effectively cure or control Valsa canker [23]. Once inside the host tissue the fungus can induce tissue maceration and cell death.…”

Genetic studies on resistance to Valsa canker in apple: genetic variance and breeding values estimated from intra- and inter-specific hybrid progeny populations

“…On the basis of the RL value of 0.6 as the cut off to separate the resistant (R) and remaining offspring (Abe et al 2007), R offspring were obtained with varying frequencies in the families derived from M. sieboldii as a parent; the overall frequency of R offspring in the families having M. sieboldii as a parent was 0.17, whereas no R offspring was produced in the families made by the intra-specific crosses of M. domestica (Table 1). …”

“…2 The relationship between mid-parental general combining ability (GCA) and specific combining ability (SCA) predictions among 23 full-sib families for resistance to Valsa ceratosperma the best parents for transmitting resistance to V. ceratosperma were M. sieboldii "Sanashi 63" (−7.768) and "Hayanarisanashi 1" (−6.411). Among the parents belonging to M. domestica, "Megumi" (−2.402) and "Golden Delicious" (−2.035) seemed to be good parents, while "Starking Delicious" (8.415), which was regarded as highly susceptible to V. ceratosperma (Abe et al 2007;Bessho et al 1994), was the poorest. Together with the data on the phenotypic values of the parental genotypes, a significant correlation (r=0.622) was observed between the normalized phenotypic values of parents and the BVs estimated by sib analysis.…”

“…The isolates were multiplied for 14 days on a PDA medium at 25°C in darkness. The preparation of the inoculum and method of inoculation followed the method developed by Suzaki et al (1997) with minor modifications based on Abe et al (2007). After a 14-day incubation, fungal mycelium was added to a 100 ml volume of sterilized water and then mildly homogenized for about 30 s. The mixture after homogenization was used as an inoculum for the excised shoot assay.…”

A Novel Indole-diterpenoid, JBIR-03 with Anti-MRSA Activity from Dichotomomyces cejpii var. cejpii NBRC 103559

“…In northern Japan, the disease is especially severe with more than 35% of orchards affected to some degree. However, information available to help with breeding against Valsa canker in apples is limited [4]. In our course of screening for anti-MRSA activity, we isolated a new indole-diterpenoid designated as JBIR-03 (1) from mycelium of Dichotomomyces cejpii var.…”