R. Lo Bianco

Effects of partial rootzone drying and rootstock vigour on growth and fruit quality of 'Pink Lady' apple trees in Mediterranean environments

We investigated the effects of partial rootzone drying (PRD) and rootstock vigour on water relations, and vegetative and productive performance of ‘Pink Lady’ apple (Malus domestica Borkh.) trees in central Sicily. In a first field trial, trees on MM.106 rootstock were subjected to: Conventional irrigation (CI), maintaining soil moisture above 80% of field capacity; PRD irrigation, where only one alternated side of the rootzone received 50% of the CI irrigation water; and continuous deficit irrigation (DI), where 50% of the CI water was equally applied to both sides of the rootzone. In a second trial, trees on M.9 or MM.106 were subjected to CI and PRD irrigation. PRD reduced stomatal conductance (gs) more consistently in trees on MM.106 than in trees on M.9, but maintained relative water content (RWC) to the levels of CI. DI induced greater gs reductions than PRD and lower RWC than CI and PRD. Rootstock vigour did not influence plant response to irrigation strategy. PRD induced some reduction in fruit number but no change in yields and fruit quality compared with CI, whereas DI reduced fruit size and marketable yields. Significant reductions in shoot and leaf growth were induced by DI, whereas only leaf growth was affected by PRD. Our observations indicate that responses induced by PRD are due to a combination of the amount and way of applying water, and not just to reductions in irrigation volumes, suggesting a possible use of PRD for increasing apple water-use efficiency in Mediterranean environments.

Fruit yield and quality responses of apple cvars Gala and Fuji to partial rootzone drying under Mediterranean conditions

Increasing irrigation efficiency is a major goal for fruit production in dry Mediterranean environments. The present study was conducted in three consecutive years (2007–09) under typical Mediterranean conditions and tested the effect of partial rootzone drying (PRD) on yield and fruit quality of two apple cultivars: Gala, with fruit maturing in summer and Fuji, with fruit maturing in autumn. Three irrigation treatments were imposed: conventional irrigation (CI), PRD (0·50 of CI water on one side of the rootzone, which was alternated periodically) and continuous deficit irrigation (DI, 0·50 of CI water on both sides of the rootzone). During the 2008 and 2009 irrigation seasons, DI reduced tree water status, and to some extent soil moisture, compared with CI and PRD. In all the years and both cultivars, DI reduced crop load by 11 and 5% over CI and PRD, respectively. In cvar Fuji, DI reduced production per tree by 9% and yield efficiency by 16% compared with CI. In all years for cvar Gala and in 2 of the 3 years for cvar Fuji, PRD and DI increased fruit soluble solid content by 5–6%, whereas PRD improved peel colour only in cvar Fuji and in 2 of the 3 years. In cvar Gala, DI fruit showed 27% more sorbitol and 55% more sucrose than PRD fruit. In both cultivars, PRD determined greater marketable yield and profit than DI. Irrigation water productivity (IWP) was increased by both PRD and DI, and in Fuji, PRD induced 18% greater IWP than DI. The different responses of the two cultivars to irrigation treatments can be attributed to differences in canopy size, crop load and mostly to the different timing of fruit growth. In particular, undergoing fast fruit growth during the irrigation period seems to induce permanent yield reductions in DI (but not PRD) trees of cvar Fuji, whereas water deficit during late fruit growth and lower crop load may have cancelled the negative effect of DI in the smaller trees of cvar Gala.

Effects of partial rootzone drying and rootstock vigour on dry matter partitioning of apple trees ( Malus domestica cvar Pink Lady)

The effects of partial rootzone drying (PRD) and rootstock vigour on dry matter accumulation and partitioning among leaves, shoots, fruits, frame and roots of apple trees ( Malus domestica Borkh. cvar Pink Lady) were investigated in 2005 near Caltavuturo, in Sicily. In a first field trial, trees on MM.106 rootstock were subjected to: conventional irrigation (CI), maintaining soil moisture above 0·80 of field capacity; PRD irrigation, where alternating sides of the rootzone received 0·50 of the CI irrigation water; and continuous deficit irrigation (DI), where 0·50 of the CI water was equally applied to both sides of the rootzone. In a second trial, trees on M.9 or MM.106 were subjected to CI and PRD irrigation. In trial 1, dry matter accumulation was markedly reduced by DI irrigation and to a lesser extent by PRD; PRD trees partitioned 20% less to leaves, 31% less to fruits and 24% more to woody components than CI trees; DI trees partitioned 14% less to current shoots and 18% more to fruits than CI and had the highest fruit:leaf ratio. In trial 2, there was no interaction between rootstock and irrigation treatments. MM.106 induced greater leaf, shoot, frame and root dry weights (DWs) than M.9, resulting in more vegetative growth and larger trees. PRD reduced leaf, shoot, frame and fruit DWs, while root DWs were similar to CI, and thus PRD trees were 18% smaller than CI trees. Neither rootstock nor irrigation affected dry matter partitioning among organs or root:canopy ratio, whereas PRD trees or trees on MM.106 showed better water use efficiency than CI and M.9, respectively. The results show that PRD trees did not activate drought tolerance strategies in terms of dry matter allocation that could improve acquisition of water resources, regardless of rootstock. PRD irrigation increased above-ground dry matter partitioning towards woody components at the expense of leaves and fruits.

Climatic characterization and phenology of local peach genotypes in the Udzungwa uplands of Tanzania

The phenology of two local peach genotypes was studied to verify whether peaches can be produced in the Tanzanian uplands. Observations were conducted on trees of one early- and one late-ripening peach genotype in 2010 and 2011. Temperature trends were reconstructed and three chilling estimation models were tested. The two peach genotypes differed for timing of flower and leaf bud-break. Common symptoms of insufficient chilling (presence of numerous stages at a specific date and about 20% of undeveloped flower buds) were observed in the late genotype. Both Utah and Dynamic models indicated low chilling accumulation, lower than the Mean Temperature model in most cases. This is inconsistent with the actual phenology, suggesting that (1) both models show some limitations under our conditions, (2) the two genotypes partly adapted to the local climate, and (3) mechanisms other than chilling (seasonal rainfall fluctuations) play a role in rest control.

Fruit Quality and Flavor Compounds Before and After Commercial Harvest of the Late-Ripening ‘Fairtime’ Peach Cultivar

ABSTRACT In this work quality of tree ripe and commercial ripe ‘Fairtime’ peach fruit was evaluated during fruit maturation and storage. Quality parameters and volatile fraction were monitored at intervals of 7-15 days from pit hardening until 10 days after commercial harvest and after 7, 17 and 24 days of refrigeration. In fruit on the tree, weight increased quadratically, diameter and peel color increased linearly, whereas flesh firmness decreased linearly. Soluble solids (SS) reached maximum levels at commercial harvest, whereas acidity started declining after commercial harvest. In the peel, esters and alcohols showed opposite trends. In the flesh, alcohols decreased quadratically and disappeared in tree ripe fruit. In refrigerated fruit, there were no significant weight changes, flesh firmness decreased linearly, SS reached a minimum around the 10th day, and acidity decreased quadratically. A three day harvest delay followed by two weeks of refrigeration may represent a chance to further extend marketing of optimum flavor ‘Fairtime’ peaches into late fall.