Founding Clones, Inbreeding, Coancestry, and Status Number of Modern Apple Cultivars

Abstract

<jats:p>Pedigrees of apple (<jats:italic>Malus</jats:italic> ×<jats:italic>domestica</jats:italic> Borkh.) cultivars were used to study worldwide genetic diversity among clones used in modern apple breeding. The most frequent founding clones were `Cox's Orange Pippin', `Golden Delicious', `Red Delicious', `Jonathan', and `McIntosh'. Coefficients of coancestry between 50 mainstream cultivars and these clones averaged 0.03, 0.12, 0.07, 0.06, and 0.02, respectively, but they were frequently as high as 0.25 with certain pairings. Among a group of 27 cultivars carrying the <jats:italic>Vf</jats:italic> gene for scab resistance, coefficients of coancestry with the five founding clones were of the same order. Although few of the cultivars sampled were substantially inbred, inbreeding could reach serious levels in their future offspring if current breeding practices are continued. The status effective number was 8 for the mainstream group and 7 for the <jats:italic>Vf</jats:italic>-carrier clones. This indicates clearly that apple breeders are operating with a population of greatly reduced genetic diversity. Careful consideration of pedigrees and increased size of the genetic base are needed in future apple breeding strategies.</jats:p>

Towards genomic selection in apple (Malus × domestica Borkh.) breeding programmes: Prospects, challenges and strategies

“…Most apple-breeding programmes worldwide are based on a narrow genetic pool; thus, the accuracy of GEBVs for selection candidates may be high because of additive-genetic relationships with the training data. Using historical pedigree records of apple cultivars, Noiton and Alspach (1996) estimated the 'status number' (which is also interpreted as the effective population size: N e ; see Lindgren and Mullin 1998) of the top-50 mainstream cultivars to be 8. These top cultivars are frequently used as parents in elite populations to develop new cultivars.…”

Characterisation of Mal d 1-related genes in Malus

“…cultivars and six additional Malus species growing at the Havelock North Research Orchard, New Zealand, were selected for analysis. The apple cultivars were selected for their close relationship to the cultivars 'Golden Delicious' or 'Granny Smith'-both of which have been shown to have high levels of Mal d 1-like proteins and to cause strong allergic responses in some people 'Jonagold' and 'Sir Prize' have 'Jonathan' in their parentage, 'Goldsmith' and 'Baujade' have 'Granny Smith' in their ancestry, and 'Royal Gala', 'Jonagold', 'Sir Prize', 'Goldsmith', 'Baujade' and 'Pink Lady' have 'Golden Delicious' in their ancestry (see Noiton and Alspach, 1996) …”

“…These studies gave no clear definitions of ripeness and harvest parameters so it has been difficult to interpret their data with respect to apple metabolic processes. We, therefore, used sixteen cultivars of Malus  domestica and 6 other species of apple, namely the putative ancestral apple species M. baccata, M. sieversii and M. sylvestris (Noiton and Alspach, 1996;Oraguzie et al, 2001) as well as M. hupehensis, M. ioensis and M. niedzwetzkyana, to compare Mal d 1-related expression during fruit ripening at both the mRNA and protein level (using a Mab that recognises an allergenic epitope in apple) to assess how much impact ripeness might have when comparing different genotypes for allergenicity and how many of the isoforms might be involved in ripening processes.…”

Development of a recurrent apple breeding programme in New Zealand: a synthesis of results, and a proposed revised breeding strategy

“…This trend toward genetic uniformity in commercial apple orchards is further accentuated by the release of additional mutants of popular cultivars (Brooks and Olmo 1994). A handful of cultivars, namely 'Cox's Orange Pippin', 'Red Delicious', 'McIntosh', 'Golden Delicious', and 'Jonathan' have frequently been used in the parentage of a large number of modern cultivars (Noiton and Alspach 1996).…”