Detached shoot treatments cannot replace whole-tree assays when phenotyping for apple resistance to Neonectria ditissima

Scheper, R.W.A.; Fisher, B.M.; Taylor, Tara; Hedderley, Duncan

doi:10.30843/nzpp.2018.71.137

Cited by 10 publications

(10 citation statements)

References 11 publications

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“…The low heritability of the detached shoot experiment (H 2 = 0.16), compared to the other phenotyping methods, indicates a large degree of variation between replicates within this experiment. This is in concordance with previous studies using this type of phenotyping assay [ 28 , 29 ]. Data from the potted tree experiment only revealed one QTL with positive evidence and had a relatively low correlation to the other canker lesion phenotypes, despite reports that similar experiments could provide sufficient resolution to differentiate between susceptible and resistant varieties [ 28 , 30 ].One influencing factor could be the timing of inoculations, as the potted trees in our experiment were inoculated while actively growing, whereas the other studies inoculated closer to leaf-fall.…”

Section: Discussionsupporting

confidence: 93%

Identification of novel genetic regions associated with resistance to European canker in apple

et al. 2022

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Background European canker, caused by the fungal pathogen Neonectria ditissima, is an economically damaging disease in apple producing regions of the world – especially in areas with moderate temperatures and high rainfall. The pathogen has a wide host range of hardwood perennial species, causing trunk cankers, dieback and branch lesions in its hosts. Although apple scion germplasm carrying partial resistance to the disease has been described, little is still known of the genetic basis for this quantitative resistance. Results Resistance to Neonectria ditissima was studied in a multiparental population of apple scions using several phenotyping methods. The studied population consists of individuals from multiple families connected through a common pedigree. The degree of disease of each individual in the population was assessed in three experiments: artificial inoculations of detached dormant shoots, potted trees in a glasshouse and in a replicated field experiment. The genetic basis of the differences in disease was studied using a pedigree-based analysis (PBA). Three quantitative trait loci (QTL), on linkage groups (LG) 6, 8 and 10 were identified in more than one of the phenotyping strategies. An additional four QTL, on LG 2, 5, 15 and 16 were only identified in the field experiment. The QTL on LG2 and 16 were further validated in a biparental population. QTL effect sizes were small to moderate with 4.3 to 19% of variance explained by a single QTL. A subsequent analysis of QTL haplotypes revealed a dynamic response to this disease, in which the estimated effect of a haplotype varied over the field time-points. Conclusions This study describes the first identified QTL associated with resistance to N. ditissima in apple scion germplasm. The results from this study show that QTL present in germplasm commonly used in apple breeding have a low to medium effect on resistance to N. ditissima. Hence, multiple QTL will need to be considered to improve resistance through breeding.

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Section: Discussionsupporting

confidence: 93%

Identification of novel genetic regions associated with resistance to European canker in apple

et al. 2022

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“…The low heritability of the detached shoot experiment (H 2 =0.16), compared to the other phenotyping methods, indicates a large degree of variation between replicates within this experiment. This is in concordance with previous studies using this type of phenotyping assay (Garkava-Gustafsson et al, 2016;Scheper et al, 2018). Data from the potted tree experiment only revealed one QTL with positive evidence and had a relatively low correlation to the other canker lesion phenotypes, despite reports that similar experiments could provide sufficient resolution to differentiate between susceptible and resistant varieties (Garkava-Gustafsson et al, 2016;Wenneker et al, 2017).…”

Section: Phenotyping Methodssupporting

confidence: 91%

Identification of novel genetic regions associated with resistance to European canker in apple

Karlström

Gómez-Cortecero

Nellist

et al. 2021

Preprint

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Resistance to Neonectria ditissima, the fungus causing European canker in apple, was studied in a multiparental population of apple scions using several phenotyping methods. The studied population consists of individuals from multiple families connected through a common pedigree. The degree of disease of each individual in the population was assessed in three experiments: artificial inoculations of detached dormant shoots, potted trees in a glasshouse and in a replicated field experiment. The genetic basis of the differences in disease was studied using a pedigree-based analysis (PBA). Three quantitative trait loci (QTL), on linkage groups (LG) 6, 8 and 10 were identified in more than one of the phenotyping strategies. An additional four QTL, on LG 2, 5, 15 and 16 were only identified in the field experiment. The QTL on LG2 and 16 were further validated in a biparental population. QTL effect sizes were small to moderate with 4.3 to 19 % of variance explained by a single QTL. A subsequent analysis of QTL haplotypes revealed a dynamic response to this disease, in which the estimated effect of a haplotype varied over the field time-points. Two groups of QTL-haplotypes could be distinguished, one that displayed increased effect and one with a constant effect across time-points. These results suggest that there are different modes of control of N. ditissima in the early stages of infection compared to later time-points of disease development. It also shows that multiple QTL will need to be considered to improve resistance to European canker in apple breeding germplasm.

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“…Significant differences in lesion length among locations were observed only once, at 12 WAI. This confirms previous observations that lesion length is less reliable than disease incidence when comparing disease progress in different treatments (Scheper et al 2018;Bus et al 2019).…”

Section: Figuresupporting

confidence: 92%

Lesion development and conidial production of <i>Neonectria ditissima </i>on apple trees in four New Zealand regions

Scheper

Vorster

Turner

et al. 2019

NZPP

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This study examined incubation period, lesion length and conidial release in Neonectria ditissima (European canker) in four New Zealand regions in relation to climatic factors. Incubation period was studied on potted ‘Royal Gala’ trees inoculated with N. ditissima. One week after inoculation, symptomless trees were dispatched to Waikato, Hawke’s Bay, Tasman, Otago and positive controls remained in a glasshouse. Conidial release was studied in trees with lesions that were dispatched to the same regions. Rain traps were placed under each lesion and conidia quantified after each rain event. Disease progress and conidial production were examined in relation to weather. Lesions developed significantly slower in Otago and faster in Waikato and the glasshouse, compared with Tasman and Hawke’s Bay. Symptom development accelerated with increasing daily hours of 11–16°C and humidity (74.6–87.2% RH). The highest conidium counts occurred in Waikato and the lowest in Otago, while conidial production started earlier in Tasman than elsewhere. Temperature is the main driver for symptom development during the incubation period and rainfall is not required. Rainfall frequency drives conidial production.

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Detached shoot treatments cannot replace whole-tree assays when phenotyping for apple resistance to Neonectria ditissima

Cited by 10 publications

References 11 publications

Identification of novel genetic regions associated with resistance to European canker in apple

Identification of novel genetic regions associated with resistance to European canker in apple

Identification of novel genetic regions associated with resistance to European canker in apple

Lesion development and conidial production of <i>Neonectria ditissima </i>on apple trees in four New Zealand regions

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