This presentation reviews some of the principals of how canopy microenvironment affects bud fruitfulness, and how these concepts can inform canopy management of dry-on-vine (DOV) raisin production on an open-gable trellis.
4. Reproductive cycle
• Two-year process
• Year 1: Flower clusters are initiated and partially
developed on microscopic shoots within buds on
green growing shoots.
• Year 2: The pre-formed microscopic shoots emerge
from dormant buds, flowers fully develop, and
bloom, fruit set, berry growth and maturation occur.
5. YEAR 1
YEAR 2
- in the developing primary bud
- on the shoot
Cluster
initiation
Rachis
elongation,
flower
initiation
Flower part
differentiation
Bloom
Pollination
&
fertilization
Berry
set
Berry softening
Harvest
11. Lateral (prompt) buds grow out the
year they are formed, resulting in
lateral shoots
12. The dormant bud arises from the most basal node of a lateral
shoot. Within the dormant node, anlage develops into shoot,
tendril or cluster primordia in the spring.
16. Sunlight promotes cluster initiation and
development and bud survival
• The number and potential size of clusters on
preformed shoots is positively correlated with
temperature, light, and carbohydrate availability in
early summer, when clusters are initiated.
• Shading reduces cluster number and potential size,
and promotes bud necrosis (death).
• Pruning: sun canes vs shade canes
22. Clusters initiated last
spring will complete
their growth this
spring, as the
preformed shoots
emerge from the
dormant nodes and
growth to full size.
During this time
cluster development
can be directly
affected by
weather, insects, nutri
tion, and other
factors.
29. The number of berries/cluster and berry size will
depend in part on pollination success. Grapes do
not require insect pollination, but poor weather and
nutrition can substantially affect set.
39. “These vigorous Thompson Seedless
Vines are crowned too low—
30 to 36 inches below the cross arm.
Much of the next year’s fruiting wood
Was totally or partially shaded during
Fruit bud initiation”.
L.P. Christensen, 1979.
40. Light levels at cordon diminish
as distance between trellis top and
cordon increases
Distance between cordon and top of trellis
14 16 18 20 22 24 26 28
Percentfullsun
0
2
4
6
8
10
12
14
16
41. Light levels at nodes 4 to 6
diminish as distance between
trellis top and cordon increases
Distance from trellis top to cordon (inches)
14 16 18 20 22 24 26 28
Percentoffullsun
0
2
4
6
8
10
12
14
16
42. Light levels at nodes 8 to 10
diminish as distance between
trellis top and cordon increases
Distance from trellis top to cordon (inches)
14 16 18 20 22 24 26 28
Percentfullsun
0
10
20
30
40
50
43.
44.
45. Conclusions
• Renewal shoots need good light exposure in spring
and summer to optimize fruitfulness in the following
season.
• Pruning is very important, but trellis design and
other canopy management practices can significantly
affect light levels in renewal zone
• Nutrition and irrigation can directly and indirectly
affect production
46. • Funding from the California Raisin
Marketing Board
• L. Peter Christensen, Mike Moriyama,
Steve Vasquez, several private growers
Acknowledgements
Hinweis der Redaktion
Cane starch content is positively correlated with bud fruitfulness. Iodine stain showing starch stored in xylem ray cells.
Determining how many nodes to keep, and which nodes (basal or apical; cane or spur, etc) can have a great impact on the number of clusters per vine, cluster size, and fruit quality. We will return to this topic shortly, with data from our recent study.
After pruning, the potential number of clusters per vine for the upcoming season has been set. However, the remaining yield components, the number of berries per cluster, berry weight and, in the case of raisins, sugar content per berry, can continue to be affected by the environment and cultural practices.
The number of flowers per cluster, and the time of flowering, will depend, in part, on environmental conditions between budbreak and bloom.
The number of berries per cluster and, to some extent, berry size, will depend in part on pollination success. Grapes do not require bees or other insects for pollination, but poor weather can reduce set.
Bud break (percent nodes with shoots) generally increases from the base of the cane towards the tip, and is higher for shorter canes compared to longer canes at most node positions. A = DOVine, B = Fiesta, C = Selma Pete, D = Thompson Seedless.
The number of clusters per node generally increases to a maximum near the middle of the cane. A = DOVine, B = Fiesta, C = Selma Pete, D = Thompson Seedless.
Average cluster weight generally increases with node position. A = DOVine, B = Fiesta, C = Selma Pete, D = Thompson Seedless.
Grape sugar levels generally decrease with node position. A = DOVine, B = Fiesta, C = Selma Pete, D = Thompson Seedless.
Selma Pete seems to have longer internodes than Thompson Seedless or other DOV raisin varieties. Make sure your pruners are actually leaving the number of nodes you expect them to.