Neck shrivel in European plum: Mechanisms and causes
Final Report Abstract
The results obtained may be summarized as follows: • Neck shrivel is a physiological disorder of European plum. Radial cuticular microcracking occurs in the neck regions of susceptible cultivars, but not in non-susceptible ones. Radial microcracking results in excessive transpiration and shrivel. • Allometric growth analysis revealed two categories of growth patterns: The first category, the ‘narrow-neck’ cultivars, showed hypoallometric growth in the neck region (i.e., slower growth than in the region of maximum diameter) during early development (stages I+II). Then later (during stage III) the neck region was ‘filled out’ by hyperallometric growth (i.e., faster than in the region of maximum diameter). This filling occurs during stage III when cuticle deposition has ceased. The second category, the ‘broad-neck’ cultivars, had more symmetrical, allometric growth (all regions grew equally fast) throughout development. • The narrow-neck cultivars exhibited extensive radial microcracking in the neck, but little microcracking in the stylar region. In contrast, broad-neck cultivars exhibited little microcracking overall without difference between neck and stylar regions. • Across all cultivars, a positive relationship was obtained for the level of microcracking in the neck region and the difference in allometric growth ratios between stage III and stages I+II, but not for the stylar region. Accelerated stage III neck growth in the narrow-neck plum cultivars was associated with more microcracking and shrivel. • During stage II (but not during stage III), the rates of xylem flow and transpiration were variable and closely related to atmospheric vapor pressure deficit. The relative contribution of xylem inflow to total sap inflow averaged 79% during stage II, decreasing to 25% during stage III. In contrast, phloem sap inflow averaged 21% of total sap inflow during stage II, increasing to 75% in stage III. • Feeding acid fuchsin to developing fruit revealed a progressive decline in dye distribution. The decline progressed basipetally, from the stylar end towards the stem end. At the mature stage III, only the pedicel/fruit junction was stained. • From results of the LDVT, the potometry and the dye infusion studies, there is no evidence for a role of vascular continuity in neck shrivel. • The Ψp values (22 ± 3 kPa) were negligibly low compared to the very negative values of ΨΠ in the stylar end (-3188 ± 73 kPa) and stem end (-3060 ± 74 kPa). • Marked differences in ΨΠ and its distribution were measured across 17 cultivars. In the majority (14), ΨΠ was more negative at the stylar end than at the stem end. In most cultivars, ΨΠ in the stylar end is more negative than in the stem end. • The absence of an axial gradient in Ψp and the small differences in ΨΠ between the stem and stylar end make both factors unlikely candidates for explaining neck shrivel.
Publications
-
Progressive Decline in Xylem Inflow into Developing Plums. HortScience, 56(10), 1263-1268.
Khanal, Bishnu P.; Acharya, Indu & Knoche, Moritz
-
Xylem, phloem and transpiration flows in developing European plums. PLOS ONE, 16(5), e0252085.
Winkler, Andreas & Knoche, Moritz
-
Water Potential, Osmotic Potential, and Cell Turgor in Developing European Plums. HortScience, 57(12), 1572-1575.
Knoche, Moritz & Grimm, Eckhard
-
Neck shrivel in European plum is caused by cuticular microcracks, resulting from rapid lateral expansion of the neck late in development. Planta, 258(3).
Khanal, Bishnu P.; Bhattarai, Anil; Aryal, Divya & Knoche, Moritz
