Peter R. Dry

Colour at harvest and post-harvest behaviour influence paprika and chilli spice quality.

Abstract Capsicum annuum L. paprika and cayenne chilli pepper fruit were grown for red spice production and harvested at various colour stages on the same day. Fruit of each stage were allowed to change colour at room temperature with or without the addition of 100 μl l−1 ethylene. Fruit appearance and colour development, and respiration and ethylene production were measured during the colouring period. Ethylene treatment had no effect on colour development or pungency for both cultivars, even though it easily crossed the cuticle, epidermis and flesh tissues into the fruit cavity. Green or deep green harvested fruit failed to fully colour red, while fruit that were harvested at or after the colour break stage visually completed their red colour development within 7–9 days. However, the colour intensity of spice powder was low for all fruit that had not developed a deep red colour prior to harvest. For paprika no difference between deep red fruit that were succulent or that had partially dried on the plant was found, but chilli fruit that had partially dried before harvest produced the most intense colour. American Spice Trade Association (ASTA) extractable red colour was the best measure of spice colour quality, compared to reflected lightness (L*), chroma (C*) and hue angle (h°) colour measurements. Pungency did not change between ripeness stages for chilli and was absent in paprika. Paprika and chilli fruit showed climacteric behaviour as long as they were attached to the plant, but when detached were non-climacteric.

The Interactive Effect of Pruning Level and Irrigation Strategy on Grape Berry Ripening and Composition in Vitis vinifera L. cv. Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment (1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. Berry size was found to decrease as node number per grapevine increased, but was not significantly altered by the PRD treatment. The influence of these treatments on the accumulation of total soluble solids per berry was investigated during berry ripening and was shown to be reduced at higher node number (120 nodes). There was no effect of PRD on the accumulation of total soluble solids. Juice titratable acidity and the concentration (per g) and content (per berry) of grape anthocyanins and phenolics were compared between treatments at harvest. In one season of the study, juice titratable acidity, anthocyanin and phenolic concentration was unaltered by the PRD treatment. In a further season, juice titratable acidity was decreased in response to the PRD treatment and was associated with increases in grape anthocyanin and phenolic concentration in response to PRD. Where there was a small increase in anthocyanin concentration in response to PRD, this was found to be independent of berry size. In addition, linear regression analysis showed a poor relationship between berry size and anthocyanin concentration, but a significant relationship was found between berry size and anthocyanins per berry.

Effect of Water Stress on the Reproductive Performance of Shiraz (Vitis vinifera L.) Grafted to Rootstocks

An experiment was conducted in the Barossa Valley, South Australia, to examine the effect of rootstocks on reproductive performance of Shiraz (Vitis vinifera L.) under water stress. Vines were grown on own roots or grafted to 110R, 1103P, 99R, Ramsey, Schwarzmann, or 140Ru. Vines either were unirrigated or irrigation was applied at 56 to 128 mm/ha across three seasons. Water stress (Ψpd < 0.8 MPa) was apparent in the unirrigated vines from veraison onward. The absence of irrigation strongly influenced vine growth and performance. Pruning weight, cane weight, and cane number were all reduced as a consequence of zero irrigation. Yields were reduced in unirrigated treatments due to a reduction in cluster number, cluster weight, and berry weight rather than fruit set or berry number. Unirrigated Ramsey was the only rootstock able to maintain yield comparable with irrigated rootstocks. Unirrigated own roots performed well in the first season but not in the second and third seasons when water stress had a negative effect on yield. Millerandage, coulure, and seedless berry numbers were the main reproductive parameters found to have a negative impact on yield and both own-rooted and grafted vines were as susceptible to these parameters. Season had a greater influence than either rootstock type or irrigation. These findings have significant implications for regions facing future drought and declining water supplies.

The interactive effect of pruning level and irrigation strategy on water use efficiency of Vitis vinifera L. cv Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment (1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. The PRD irrigation technique was applied to a single side of the grapevine rootzone at a time, 45 cm from the trunk, and the sides were switched in 10-day cycles. For the standard irrigation treatment, both sides of the grapevine were irrigated. At the end of an irrigation cycle, the PRD treatment resulted in reduced midday readings of stomatal conductance and stem (ψS) and leaf (ψL) water potential relative to the control treatment. During the switch between irrigation cycles, when the soil water profile of both the ‘wet’ and ‘dry’ sides of the PRD-treated grapevines was refilled, stomatal conductance, ψS and ψL were restored to the same levels as for the control experiment. As node number per grapevine increased, berry size and winter pruning weight were reduced and yield increased. In the first season of the experiment, the PRD treatment did not have a significant effect on berry size, yield and pruning weight, although shoot length was reduced in response to PRD for all the pruning treatments. In a subsequent season, PRD was found to reduce yield, primarily through a reduction in berry set. Water use efficiency measured as t/ML irrigation water applied was increased significantly as crop load increased, and was enhanced in response to the PRD irrigation technique.

Rootstock Effects on Primary Bud Necrosis, Bud Fertility, and Carbohydrate Storage in Shiraz

Shiraz grapevines (Vitis vinifera L.) grafted to three different hybrid (American Vitis) rootstocks at two sites were used to evaluate the effect of rootstock on primary bud necrosis (PBN), fruitfulness, and carbohydrate storage. Buds were dissected during winter dormancy and assessed for the number of inflorescence primordia and incidence of primary bud necrosis. Trunks, canes, and roots were sampled at dormancy for carbohydrate concentration. A water deficit treatment was also applied at one of the two locations. Fruitfulness and yield were affected by water deficit. Rootstock type influenced the incidence of primary bud necrosis, fruitfulness, and carbohydrate concentration at both sites.

Effect of vine age on vine performance of Shiraz in the Barossa Valley, Australia

Background and Aims Old vineyards are often suggested to be superior to younger ones, a claim that has scarcely been investigated scientifically. The aim of this study was to investigate if vineyard age influences vine performance. Methods and Results Five commercial Shiraz vineyards in the Barossa Valley, SA, were selected; each site contained younger vines, which had been vegetatively propagated from older vines on the same site. Measurements of vegetative growth and reproductive development were obtained over three seasons. Results show that the effect of vine age is difficult to measure and separate from seasonal and site interactions. Vine age was strongly correlated with trunk circumference. Vines aged 49 years showed more similarities with older vines (93–168 years old) than with younger vines (6–28 years old). Conclusions Vine age had an impact on grapevine reproductive performance. Older vines produced a yield greater than that of younger vines. Greater vine size, measured by increase in trunk circumference over time, may be a key determining factor in increased reproductive capacity. Significance of the Study Vine age is commonly attributed to superior vine performance, as a precursor to fruit and wine quality. Our findings suggest that increasing vine age had a positive effect on reproductive performance in terms of yield, contrary to popular belief. This establishes a starting point for future studies that are underway to quantify if these findings have an effect on fruit and wine composition and sensory attributes.