Growth habit, the effect of shading and soil moisture content on primocane growth of Rubus spp. native to the Tohoku Region in Japan.

摘要

Many Rubus species are native to Japan, but no cultivars have been bred from them. To evaluate these native Rubus species for genetic resources, two experiments were carried out. Experiment 1 was a qualitative study, four native Rubus spp. were compared with each other as well as with six cultivars of commercial relevance, which were introduced from foreign countries. The native Japanese Rubus spp. were: R. crataegifolius, R. palmatus, R. parvifolius and R. phenicolasius. The imported cultivars were: Brandywine, Boysen, Schoenemann, Hanover, Trailblazer and Burbank Thornless. These four species and the six cultivars were planted in a field, 4 m apart on 10 April 2002. Parameters such as growth habit and primocane length were investigated when primocane growth had been completed in 2003. In experiment 2, suckers derived from one individual each of R. crataegifolius and R. palmatus were planted in 20 plastic pots on 12 April, 2004. Five pots were placed in four different conditions on 12 June in 2004: two light levels (100 and 22% relative illumination) and two soil moisture content levels (standard watering and excessive watering), resulting in four treatments with five replicate plants per species. Primocane length and chlorophyll content of the leaves were investigated on five occasions between 21 June and 21 August 2004. The results of experiment 1 show that growth habit was erect for R. crataegifolius and R. palmatus, intermediate for R. phoenicolasius and spreading for R. parvifolius. The length of primocane in R. crataegifolius, R. parvifolius and R. phoenicolasius was comparable to the six cultivars. Compared to the cultivars the diameter of the cane at 10 cm from soil level in R. crataegifolius and R. phoenicolasius was larger, and in R. palmatus and R. parvifolius was smaller. The number of suckers in R. crataegifolius was higher than those found in the cultivars, whereas the number of suckers in the other three native species was the same as those produced by the cultivars. In experiment 2, the chlorophyll content of leaves was higher and the primocane growth was improved in the shade treatment compared to those in full light in R. crataegifolius and R. palmatus. Tolerance to excessive watering is thought to be stronger in R. palmatus than in R. crataegifolius. Plant growth under excessive watering in the full light treatment was markedly suppressed in both species. Judging from the growth habit, R. crataegifolius, R. parvifolius and R. phoenicolasius are the most promising species for genetic resources. The environmental experiment (2) revealed that light level was the key factor, although adequate soil moisture was also found to be vital for the successful cultivation of the Rubus species investigated here. The difference in stress tolerance between species should be considered at cultivation and could be used for the selection of genetic resources.