New insights for estimating the genetic value of segregating apple progenies for irregular bearing during the first years of tree production

Abstract

Because irregular bearing generates major agronomic issues in fruit-tree species, particularly in apple, the selection of regular cultivars is desirable. Here, we aimed to define methods and descriptors allowing a diagnostic for bearing behaviour during the first years of tree maturity, when tree production is increasing. Flowering occurrences were collected at whole-tree and (annual) shoot scales on a segregating apple population. At both scales, the number of inflorescences over the years was modelled. Two descriptors were derived from model residuals: a new biennial bearing index, based on deviation around yield trend over years and an autoregressive coefficient, which represents dependency between consecutive yields. At the shoot scale, entropy was also considered to represent the within-tree flowering synchronicity. Clusters of genotypes with similar bearing behaviours were built. Both descriptors at the whole-tree and shoot scales were consistent for most genotypes and were used to discriminate regular from biennial and irregular genotypes. Quantitative trait loci were detected for the new biennial bearing index at both scales. Combining descriptors at a local scale with entropy showed that regular bearing at the tree scale may result from different strategies of synchronization in flowering at the local scale. The proposed methods and indices open an avenue to quantify bearing behaviour during the first years of tree maturity and to capture genetic variations. Their extension to other progenies and species, possible variants of descriptors, and their use in breeding programmes considering a limited number of years or fruit yields are discussed.

Precocity and a long-term cropping in apple progenies grown on M 9 rootstock

“…Our results concerning the effect of high and extremely high fruit set on biennial bearing occurrence are also in agreement with data in existing literature (Guitton et al 2012;Durand et al 2013;Celton et al 2014).…”

“…Two descriptors were proposed recently for the description of biennial bearing: a new biennial bearing index, based on the deviation around yield trend over years and an autoregressive coefficient, which represents dependency between consecutive yields (Durand et al 2013).…”

Development of a high-density cranberry SSR linkage map for comparative genetic analysis and trait detection

“…Biennial bearing is a complex problem which affects the economic livelihood of commercial orchards of a variety of fruit crops from diverse taxonomies such as apples, pears, oranges, and pistachios (Jonkers 1979;Smith et al 2004;Kallsen et al 2007). As a result, extensive research has been conducted in order to understand the environmental components affecting biennial bearing using BBI (Wilcox 1944;Jonkers 1979;Stevenson and Shackel 1998;Smith and Samach 2013) as well as identifying genotypic variation affecting biennial bearing tendencies using more complex adaptations of BBI (Guitton et al 2012;Durand et al 2013). Multiple putative QTL related to biennial bearing have been identified in apple (Guitton et al 2012).…”

Genetics and Genomics of Tree Architecture

“…Costes et al, 2014;Wilkie et al, 2008). At the tree level, the timing of floral induction may vary depending on the type of axis and its position (Costes et al, 2003;Costes et al, 2014), and complex patterns of synchronization versus resynchronization may be observed between shoots and branches within the tree (Durand et al, 2013;Monselise & Goldschmidt, 1982). Superabundance and synchronized fruit/seeds productions have also been reported in some noncultivated perennial species, and is known as 'masting' (Samach & Smith, 2013).…”

“…In apple tree, several propositions have been formulated for promoting either dwarfed spur types (Dickman, Gold, & Flore, 1994) or trees characterized by long and weeping branching (Type IV) which were considered prone to regular bearing (Laurens et al, 2000;Lespinasse, 1992). Recently, new indices able to estimate alternate bearing behaviour have been proposed which could be applicable on young trees during the early production period, when production per tree is still increasing over years (Durand et al, 2013). In all species, it must be underlined that breeding these ideotypes may be seriously limited by unfavourable correlations due to negative pleiotropic effects of the genes involved (Da Silva et al, 2014;Han et al, 2012;Wu, 1998).…”