A Study on Cross Breeding between Triploid and Diploid Apple Cultivars

在苹果的杂交育种中，迄今很少采用三倍体品种（3x）作为育种材料。即，在二倍体品种（2x）之间进行杂交已成为一种实践。在这种情况下，本研究旨在建立苹果三倍体与二倍体品种杂交育种的方法。因此，将三倍体与二倍体品种进行互交育苗，并对其生长、开花、结果、性状等进行比较。在幼树生长方面，2x * 3x杂交的幼苗优于3x * 2x杂交的幼苗。在2x * 3x幼苗中，与2x * 2x幼苗生长旺盛的占39% ~ 54%。2 × 3 × 3幼苗有相当多的矮化现象。将2x * 3x的幼苗嫁接到补足砧木苹果上，根据树干周长指数评价，约50%的幼苗矮化。因此，可以清楚地认识到，嫁接到生长型砧木上，也会出现2x * 3x的矮化杂交苗。3 .在开花结果方面，2x * 3x杂交苗不如2x * 2x杂交苗，但明显优于3x * 2x杂交苗。播后7年，杂交苗的果实性状随杂交组合的不同而有所差异，但2x * 3x与2x * 2x杂交苗之间无明显差异。然而，这些幼苗刚刚达到生育年龄，因此调查应继续深入。这些结果表明，以二倍体品种为种亲本，以三倍体品种为花粉亲本，可以很好地进行杂交育种，并且产生矮化品种的可能性很大。

In cross breeding of apple, triploid cultivars (3x) have been scarcely employed hitherto as the breeding materials. Namely, it has been a practice to perform intercrosses among diploid cultivars (2x). Under these circumstances, this study aims at establishing a method of cross breeding between triploid and diploid apple cultivars. Thus, seedlings were grown from reciprocal crosses between triploid and diploid cultivars and comparison was made on the tree growth, flowering, bearing, fruit characteristics, etc.1. Regarding the growth of young trees, seedlings of 2x * 3x crosses were superior to 3x * 2x seedlings. Among the 2x * 3x seedlings, those showing vigorous growth comparable to 2x * 2x seedlings amounted to 39 to 54%. A considerably large number of the 2x * 3x seedlings showed dwarfness.2. When the 2x * 3x seedlings were grafted on vigorating rootstocks, Malus prunifolia, about 50% of the seedlings showed dwarfness evaluated on the basis of trunk circumference index. Thus, it was clearly recognized that dwarf cross seedlings of 2x * 3x also showed when grafted onto vigorating rootstocks.3. In flowering and fruiting, the cross seedlings of 2x * 3x were inferior to the 2x * 2x seedlings but clearly superior to the 3x * 2x ones.4. Seven years after sowing, the cross seedlings showed difference in fruit characteristics depending on cross combination, though no clear difference was observed between the 2x * 3x seedlings and the 2x * 2x ones. However, these seedlings have just attained the bearing age and therefore the investigation should be continued further.These results indicate that cross breeding can be well performed by using a diploid cultivar as the seed parent and a triploid cultivar as the pollen parent, and that there is a high possibility of creating a dwarf cultivar.