Calcium accumulation in developing fruits of raspberry and blackberry

A. Dias Da Silva, S. Orr, M. Kraft, M. Hardigan, B. Maupin, R. Pio, D.R. Bryla, L.W. DeVetter
Calcium (Ca) is an essential macronutrient associated with fruit quality across many horticultural crops. Growers frequently apply Ca to promote fruit quality, but there are no studies reporting the best stages for Ca fertilizer application in caneberry. The objective of this study was to determine the timing and peak uptake periods of Ca in the fruits of raspberry (Rubus idaeus) and blackberry (Rubus sp.) to inform fertilizer application strategies. Fruits were collected at seven stages of development from three floricane-fruiting raspberry (‘Meeker’, ‘WakeField’, and ‘WakeHaven’) and three trailing blackberry (‘Marion’, ‘Black Diamond’, and ‘Columbia Star’) cultivars in 2022. Fruit samples were analyzed for Ca using an inductively coupled plasma optical emission spectrometer. Scanning electron microscopy (SEM) was also performed on a subset of ‘Meeker’ raspberries to explore micro-surface morphology that could influence Ca uptake dynamics. The peak period of Ca uptake was from stage S4 (half developed/“immature green”) to S6 (immature fruit/“white fruit”) across the raspberry cultivars and from stage S4 to S5 (mature green) in ‘Black Diamond’ and S4 to S6 in ‘Columbia Star’ and ‘Marion’ trailing blackberry. Little to no uptake of Ca was observed in the fruit or receptacle tissues before these stages. Fruit Ca uptake appeared greatest in ‘Meeker’ through S6, but ‘WakeHaven’ retained more Ca than ‘Meeker’ or ‘WakeField’ at S7 (“ripe fruit”). Unlike raspberries, blackberries continued to accumulate Ca between stages S6 and S7, which was attributed to retention of the receptacle in ripe fruit. SEM micrographs revealed a greater density of filamentous, epidermal hairs at S5 when compared to S6 and S7, which may impact Ca uptake via foliar fertilizers. Overall, findings from this study suggest that Ca fertilizer applications should be targeted between stages S4 to S6 to coincide with peak periods of plant uptake.
Dias Da Silva, A., Orr, S., Kraft, M., Hardigan, M., Maupin, B., Pio, R., Bryla, D.R. and DeVetter, L.W. (2024). Calcium accumulation in developing fruits of raspberry and blackberry. Acta Hortic. 1388, 339-346
DOI: 10.17660/ActaHortic.2024.1388.49
Rubus, plant nutrition, tissue analysis, foliar feeding, accumulation of nutrients, march of nutrient absorption, dry matter accumulation

Acta Horticulturae