Mohamed Ghrab

The behaviour of peach cultivars under warm climatic conditions in the Mediterranean area

Peach production will eventually suffer from the temperature changes initiated by global warming. This study investigates the response of peach cultivars to exceptional warm winter conditions. Fifteen peach cultivars from three production areas in the north and the centre of Tunisia were surveyed during 2006 and 2007. Flowering date and period, vegetative growth, yield and fruit quality were monitored. During a warmer year, chill accumulation represents less than 50% of the average chilling accumulation for the three production areas and less than 35% of the previous year’s accumulation. The lack of chilling had variable consequences on peach species, depending on cultivars. Delayed flowering, extended flowering period, weak vegetative growth and high heterogeneity of fruit size were observed. Bud break and flowering were delayed by 6–17 days, and the flowering period was extended by 4–10 days. Early cultivars seem to be in general less sensitive to low chill accumulation. Nevertheless, some early, mid-season and late ripening cultivars were severely affected and seem to be highly sensitive to warm conditions. With the increasing frequency of warmer winters, planting early ripening and low chilling cultivars and adopting new practices that increase assimilation could compensate for the effect of the observed anomalies.

EFFECTIVE HYDROGEN CYANAMIDE (DORMEX®) APPLICATION FOR BUD BREAK, FLOWERING AND NUT YIELD OF PISTACHIO TREES CV. MATEUR IN WARM GROWING AREAS

Climate change characterized by global warming is expected to have an incidence on fruit trees’ development and production. The severity of these effects depends on lack of chilling. The current study focused on the research of an optimal dose of hydrogen cyanamide (Dormex®) treatment which can advance the bud break of female pistachio trees ( Pistacia vera L.) to ensure better blooming synchronization with pollinators. A field experiment was conducted in northern Tunisia (36°49′N, 9°48′E) on mature pistachio trees. Two hydrogen cyanamide treatments at 2% and 4% Dormex® were applied with reference to the control untreated trees. The flowering time, vegetative growth, starch content, productivity and nut characters were followed. Results show that 4% Dormex® advanced the normal bud break by 15 days and flowering by 11 days and improved natural pollination by synchronization of male and female flowers. Consequently, fresh yield and nut quality as split and blank rates and nut weight were improved. However, shoot growth, leaf area and starch content in current shoot seemed unaffected by hydrogen cyanamide applications. In conclusion, hydrogen cyanamide could be used as 4% Dormex® and sprayed 45 days before bud break to improve pistachio productivity and prevent anomalies of lack of chilling due to global warming that could be more frequent in the Mediterranean areas.

Effect of Hydrogen Cyanamide on Vegetative Growth, Yield, and Fruit Quality of Fig cv. Zidi in a Warm Production Area

ABSTRACT The fig tree (Ficus carica L.) is widely cultivated in the Mediterranean region under warm climates. Fig yield is governed by the previous crop load and is strongly dependent on shoot length. Special cultural practices are required to stimulate new vegetative growth that will ensure regular and high productivity. The present study focused on the use of the rest breaking agent hydrogen cyanamide (HC) as Dormex to enhance vegetative growth, which influences the yield. A field trial was held in northern Tunisia (36° 49′ N; 9° 48′ E) on mature fig trees cv. Zidi. In reference to untreated trees as control, two hydrogen cyanamide treatments at 1% and 1.5% HC were considered. Bud break rate, vegetative growth, starch content of shoots, yield, and fruit characteristics were assessed. Results indicated that 1.5% HC significantly increased shoot length, fruit number per shoot, and yield. It advanced bud break by 10 days and fruit ripening by 7 days compared to the control. However, leaf number, leaf area, and starch content seem to be unaffected by hydrogen cyanamide treatments. Regarding fruit quality, a 1.5% HC dose significantly increased dry matter content, while fruit diameter and total soluble solids remain unaffected. In conclusion, hydrogen cyanamide could be used under warm conditions to improve vegetative growth of fig trees cv. Zidi and consequently fig productivity. Application of 1.5% HC 40 days before bud break was the most effective in increasing shoot length and yield.

Phenology and Yield Efficiency of Early, Mid-, and Late-Maturing Cultivars of Peach in Irrigated Orchards under Mediterranean Climate

ABSTRACT Productivity of peach cultivars with different ripening seasons was studied under the growers’ conventional conditions of Tunisia. Experiments were performed in northern Tunisia (36° 41ʹ N, 10° 15ʹ E). Performances of Flordastar, Royal Glory, and Carnival as respectively early, mid-season, and late ripening cultivars were evaluated under the grower’s conventional irrigation programs. Fruit growth, yield, water supply, and water productivity were determined through four years. For the three cultivars, Flordastar, Royal Glory, and Carnival, fruit maturity was achieved at 650, 1100, and 2200 GDD, respectively. Average yields were 17.4, 29.8, and 41.1 t ha–1 and mean values of water productivity were 1.9, 3.1, and 3.6 kg fresh yield m–3 for early, mid-season, and late cultivars, respectively. Results of agronomic performances evaluation at the farm scale provided a reference on the behavior of early, mid-season, and late cultivars of peach in irrigated orchards in semi-arid conditions.