Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 90

A cherimoya breeding programme was begun in the 1990s at the IHSM ‘La Mayora’ in Spain, where a germplasm collection of cherimoya cultivars with over 350 accessions is conserved. Advanced selections have been made to complement the main cultivar in the region, ‘Fino de Jete’. A new selection ‘Alboran’ that is under registration shows lower seed index than ‘Fino de Jete’ and excellent organoleptic properties during winter and spring months under Mediterranean conditions. This germplasm collection contains a spontaneous mutant of A. squamosa ‘Thai seedless’ that produces fully seedless, normal-size fruits. A genetic and molecular characterization of the ovule of ‘Thai seedless’ revealed the absence of the INNER NO OUTER (INO) gene, that is involved in the development of the outer integument of the ovule (Lora et al., 2011b). An ongoing breeding objective is to introduce this trait into cherimoya using ‘Thai seedless’ as the male parent and ‘Fino de Jete’ as the female parent. Several naturally occurring triploid and one tetraploid atemoyas have been obtained from the ‘Thai seedless’ × ‘Fino de Jete’ cross. Triploid individuals have also been obtained from backcrossings (A. cherimola × atemoya), self-crossings (atemoya × atemoya) and intraspecific crosses (A. cherimola × A. cherimola) (Martín et al., 2019). In those countries where cherimoya originated, despite the high genetic diversity, few breeding programmes have been established (Pinto et al., 2005). In those regions, the development of better management of this crop during flowering, postharvest and promotion could significantly improve the quality and production of cherimoya (Van Damme and Scheldeman, 1999; Vanhove and Van Damme, 2013). Several cultivars have also been selected in Italy (Pinto et al., 2005) and Madeira (Portugal) (Nunes, 1997).

Atemoya breeding programmes have been established in Australia, Florida (USA) and Brazil. In Australia interspecific hybrids using A. cherimola, A. squamosa, A. reticulata and A. diversifolia have been reported; some cultivars produce fruit with red skin colour and pink internal, symmetrical shape, flesh recovery and excellent flavour (George et al., 1999, 2002, 2005). Some triploid seedless selections were obtained after crossing tetraploid and diploid genotypes (George et al., 1999). In Florida, breeding of atemoya was initiated in the early 1900s (Wester, 1913) but the programme is no longer active. In Brazil the spontaneous seedless A. squamosa mutant ‘Thai seedless’ has been used for breeding (Mendes et al., 2012). In pawpaw, although the crop is still in the early stages of domestication, breeding and selection in Kentucky began in c.1900 and the programme at Kentucky State University that started in the 1990s has resulted in several advanced selections (Peterson, 2003; Pomper et al., 2008). Triploid mutants have been occasionally reported in A. triloba (Bowden, 1949).