Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Temporal yield variability in subtropical table grape production Kishor C. Dahal a, ⁎ , Surya P. Bhattarai a , David J. Midmore a , David R. Oag b , Kerry B. Walsh a a Institute for Future Farming Systems, Central Queensland University, Australia b Department of Agriculture and Fisheries, QLD Government, Australia ARTICLE INFO Keywords: Alternate bearing Biennial bearing Irregular bearing Vineyard Grapevine ABSTRACT Inconsistent yield between seasons for table grape cultivars grown in subtropical climates in Australia presents a challenge to the industry in terms of marketing and economic sustainability. The pattern of this yield incon- sistency has not been described. Marketable fruit yields of three cultivars (Red Globe (RG), Menindee Seedless (MS) and Flame Seedless (FS)) were acquired over 14 seasons, and individual vine yields of MS were collected for a four-season period from a vineyard in the Central Highlands of Queensland, Australia. Cultivars FS and RG did not show an alternate bearing pattern. Yields of MS varied up to four-fold in consecutive seasons. An al- ternate yielding pattern as measured by the indicators of an alternate bearing index (I) and associated prob- ability calculated using a resampling process was evident in 7 (2009–2015) of the 14 monitored seasons. Individual vine yield over the four-season period 2014–2017 was irregular and 90% variation in vine yields was due to the variation in the number of bunches per vine. The seasonal yield variation of MS was partly explained (R 2 = 0.31, P < 0.05) by the mean monthly temperature in October of the year preceding harvest. This result is ascribed to the effect of high temperature during inflorescence initiation and early development which occurs in October in the Central Highlands of Queensland. 1. Introduction Temporal (inter-annual) variation in crop yield has been described for a number of fruit crops, with these patterns broadly defined as al- ternate (biennial) or irregular. For example, an alternate bearing pat- tern (‘on year’ with heavy yield followed by ‘off year’ with little or no yield) has been reported in mango, pistachio, pecan, avocados, apple, olive and citrus (Monselise and Goldschmidt, 1982). The extent of bi- enniality can be influenced by many factors, including tree age (Smith et al., 2004), rootstock (Cantuarias-Avilés et al., 2011), variety (e.g., for mango (Shivashankara and Mathai, 1995)), and extent of pruning (Andersen et al., 1996). Alternate bearing is commonly ascribed to ei- ther a growth regulator effect (e.g., high GA 3 levels associated with a heavy crop may inhibit inflorescence primordium (IP) development, and thus reduce yield in the following season), or a carbohydrate competition effect (with a heavy fruit crop competing for resources with IP) (Goldschmidt and Golomb, 1982; Lavee, 1989). In the carbo- hydrate competition explanation for alternate bearing, storage reserves of carbohydrates are exhausted during the ‘on year’ of high yield, af- fecting IP development and thus following season yield (Monselise and Goldschmidt, 1982). An area wide perturbation can result in synchro- nisation between trees in terms of alternate bearing. Rosenstock et al. (2010) reported that 58% of trees in a pistachio orchard of 4288 trees demonstrated synchrony in alternate bearing over a six-year period. Grapevine (V. vinifera L.) has not been reported as an alternate/ irregular crop; however, seasonal yield variations are commonly re- ported in different growing regions. For example, in an analysis of yield stability of 16 crops in selected European countries over 75 years, Chloupek et al. (2004) reported the highest variation between years for wine grapes (33%) and the lowest for cereals (10%). Various long-term records from vineyards of cooler climates of south-east Australia in- dicate a tendency toward alternate bearing but these patterns are not pronounced (Clingeleffer et al., 2001). Inter-seasonal yield variation (and a gradual decrease) in wine grape varieties has also been reported in New Zealand (Trought and Bramley, 2011). A table grape crop can yield 20 t ha -1 , or approximately 3 kg dry weight per vine from a vine of total dry weight reported at 10–12 kg (Oag, 2007). This level of production may implicate exhaustion of storage reserves, setting the vine up for a subsequent ‘off year’. Tem- poral yield variation in grapevine has been associated with pruning and crop load management practices that impact carbohydrate availability. In muscadine grapevine (V. rotundifolia), Andersen et al. (1996) re- ported that an additional level of pruning in alternate years resulted in alternate yields of heavy and light crops. In contrast, Keller et al. (2004) https://doi.org/10.1016/j.scienta.2018.11.063 Received 28 May 2018; Received in revised form 20 November 2018; Accepted 21 November 2018 ⁎ Corresponding author at: Building 361 CQUniversity, Rockhampton, QLD, 4701, Australia. E-mail addresses: k.dahal@cqu.edu.au, k.dahal@iaas.edu.np (K.C. Dahal). Scientia Horticulturae 246 (2019) 951–956 0304-4238/ © 2018 Elsevier B.V. All rights reserved. T