Comparison of the establishment efficiency of well-grown seedlings at the early growth stage from reciprocal crosses between diploid and triploid apple [Malus pumila] cultivars, and the possibility of these cultivars cross breeding
2007
Sato, M.(Akita Prefectural Coll. of Agriculture, Ohgata (Japan)) | Kanbe, K.
This study investigated the possibility of performing cross breeding between diploid (2x) and triploid (3x) apple cultivars. Well-grown king flowers of 2x were hand-pollinated with an abundance of pollen grains from the 3x; thinning for open-pollinated fruitlets on the experimental trees was carried out twice for the 2x x 3x, 3x x 2x and 2x x 2x crosses. Thereafter, the three types of crosses were compared for fruit set, seed formation, seedling growth at the early growth stage, and the number of well-grown seedlings established from 100 flowers crossed. Fruit set 60 days after pollination was 71.1 to 81.6% and 92.9 to 98.0% for 3x x 2x and 2x x 2x, respectively. For 2x x 3x, however, fruit set ranged from only 16.5 to 36.5%. Rate of normal seed formation was 76.5 to 77.5% for 2x x 2x, but only 16.5 to 42.6% for 2x x 3x and 9.4 to 33.6% for 3x x 2x. Rate of wellgrown seedlings 1 year after sowing ranged from 47.3 to 54.0% and 2.4 to 7.2% for 2x x 3x and 3x x 2x, respectively, and 72.4 to 94.1% for 2x x 2x. Number of well-grown seedlings established from 100 flowers crossed was 456 to 772 for 2x x 2x, 24 to 93 for 2x x 3x and 1 to 13 for 3x x 2x; it was found that more well-grown seedlings can be obtained for 2x x 3x than for 3x x 2x, using the techniques of pollinating and fruit thinning described above. These findings show that cross breeding for a new apple cultivar will be successful for 2x x 3x, though the cross is less efficient for breeding than the 2x x 2x. Breeding from a 3x x 2x cross will have little success.
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