Heat Unit Requirements of "Flame Seedless" Table Grape: A Tool to Predict Its Harvest Period in Protected Cultivation.

Francisca Alonso,Mónica González,Juan J Hueso,Julián Cuevas,Fernando M Chiamolera

doi:10.3390/plants10050904

Abstract

Greenhouse cultivation of table grapes is a challenge due to difficulties imposed by their perennial habit and chilling requirements. Despite difficulties, greenhouse cultivation allows ripening long before that in the open field. Nonetheless, for harvesting “Flame Seedless” in the most profitable periods, a cultural practices timetable has to be established. In this context, an estimation of development rate as a function of temperature becomes essential. This work puts forward a procedure to determine “Flame Seedless” threshold temperatures and heat requirements from bud break to ripening. “Flame Seedless” required an average of 1633 growing degree days (GDD) in the open field with a base temperature of 5 °C and an upper threshold temperature of 30 °C. Strikingly, only 1542 GDD were required within the greenhouse. This procedure forecast “Flame Seedless” ripening with an accuracy of three and six days in the open field and greenhouse, improving predictions based on the average number of days between bud break and ripening. The procedure to predict oncoming harvest date was found satisfactory, just four days earlier than the real date. If we used the typical meteorological year instead of the average year, then the prediction was greatly improved since harvest was forecast just one day before its occurrence.

Highlights

Protected cultivation is a common orientation for the production of out of season vegetables in Southeast Spain, home of the world’s largest concentration of greenhouses
Tbhfeolre“aFstlaCmVe(S5.e7e7d%le)sws”a.s found at 5 ◦C. This temperature (5 ◦C) and, this value is proposed as TbWfoeru“sFeldamtheeSseaemdelepssr”o.cedure for calculating Tu, this time in the range of 25–45 °C
Table grape allowed us to predict its ripening with an error of just three days, improving our capacity to forecast harvest date in comparison with the usual method based on counting the number of days between bud break and ripening

Summary

Introduction

Protected cultivation is a common orientation for the production of out of season vegetables in Southeast Spain, home of the world’s largest concentration of greenhouses. In the case of temperate zone fruit trees and vines, the need to satisfy their chilling requirements for bud break constitutes an additional challenge for managing these crops under greenhouses. Previous research has shown that covering “Flame Seedless” table grape plants with plastic in early December accelerates harvest by one month with respect to plants grown in a nearby vineyard in the open field [5]. This success is explained because the greenhouse provides suitable temperatures early in the season when outdoor conditions are low for bud break and initial shoot growth. The precise climate control achieved in modern greenhouses and the low chilling requirements of “Flame Seedless” table grape allow its harvest to be scheduled in early June (Northern Hemisphere) when prices are very high

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