SPUR TYPE GROWTH HABIT IN APPLES
After several year's evaluation of a variety collection of 645 original varieties at Holovousy made it possible to distinguish 31 spur and semi spur varieties (e.i. 4.8 %), 6 of them being distinct spur types similar to the best mutants (like 'Mac Spur'). As concerning the hybridization programme so far only crosses were evaluated that were not crossed with the aim to obtaim spur type varieties. From the whole lot of 9 221 seedlings 603 ones (6,5 %) shows a spur type character, from which 41 (0.4 %) could be of distinct dwarf (sturdy) spur types. The highest proportion of the desirable growth types segregates in the crosses of spur type varieties, then after selfing of some varieties or in the case of sib crosses. That confirms a recessive type of heritability. During the 15 year's programme of mutation breeding a serie of perspective spur type mutants has been obtained from 6 varieties, while it has not been successful with another 4 varieties. Further more than 20 spur type mutants of foreign origin is being evaluated. The spur types show a rather great variability concerning the degree of spurring and dwarfing. The evaluation of growth habit can be influenced by a rootstock, climatic conditions and planting density.
Blazek, J. (1985). SPUR TYPE GROWTH HABIT IN APPLES. Acta Hortic. 159, 69-76