Orchard estimates of blush coverage in pears
Research & ExtensionCrop mapping technology can scan, estimate and forecast red-colour coverage in blush pear cultivars.
Ricó pears growing at Seeka in the Goulburn Valley.
Photo: Abram Rasmussen Photography
Blush pear cultivars have been the focus of several international breeding programs because of export demand for high-quality red-colour peel coverage. It is one of the most important fruit quality features of red-coloured pears – the attractive appearance being associated with health benefits by overseas consumers.
Blush pear cultivars ANP-0118 and ANP-0131 originate from a large Victorian breeding program that produced 143 pear selections from thousands of cultivar crosses. In these two cultivars, commercially available as LanyaTM and RicóTM, blush coverage (percentage) is the key quality attribute in achieving a premium market price.
As a component of the PIPS3 Program’s Developing smarter and sustainable pear orchards to maximise fruit quality, yield and labour efficiency (AP19005) project, Agriculture Victoria has been working closely with Australian agtech company Green Atlas to estimate crop parameters such as fruit number, fruit size and fruit skin colour by scanning orchards with the commercially available mobile platform Cartographer. Recent research has demonstrated the ability to use the Green Atlas technology to accurately measure colour development in peach and nectarine orchards with a colour development index (CDI) ranging from 0 (green) to 1 (red). The accuracy of CDI maps to describe and track redness development was further validated with apple cultivar Ruby Matilda.
In 2021 and 2022, the Agriculture Victoria Research team at the Tatura SmartFarm studied the relationship between CDI and percentage of blush coverage in ANP-0118 and ANP-0131 pears. CDI was measured using the Cartographer in January 2021 and 2022, i.e. at harvest in ANP-0118 and a month prior to harvest in ANP-0131 pears. Blush coverage was assessed at harvest using an inline commercial grader (Compac InVision 9000). Figure 1 shows that the relationship between CDI and grader measures of blush coverage was robust and the prediction error was below 5 per cent.
Figure 1: Relationship between percentage of blush coverage measured with a commercial grader and colour development index (CDI) measured with Cartographer. Results are from a pooled sample of ANP-0118 and ANP-0131 pears in 2021 and 2022. Points represent averages of experimental plots.
The relationship shown in Figure 1 was used to model blush coverage in a commercial ANP-0131 orchard (Calimna Orchard, Ardmona) before the 2022 harvest. The map in Figure 2 shows the spatial variability of blush coverage in the commercial orchard, with a few hotspots with higher blush development that were correlated with relatively lower leaf area.
Figure 2: Block map of percentage of blush coverage obtained in a commercial ANP-0131 block (Calimna Orchard, Ardmona) in 2022.
Additionally, the predicted distribution of percentage of blush coverage was compared with the distribution of blush coverage obtained at harvest with the commercial grader. The distributions were compared using five-class (bin) histograms for the 0–20, 21–40, 41–60, 61–80 and 81–100 per cent blush coverage ranges. Our findings suggest that the prediction of blush coverage classes showed errors consistently lower than 5 per cent for each blush coverage class in both 2021 and 2022 harvests. The highest error (4.9 per cent) was obtained in 2021 for the 40–60 per cent blush coverage class.
Figure 3: Five-class histograms showing distributions of blush coverage estimated with an inline grader (blue bars) and predicted using Green Atlas Cartographer (red bars).
Accurate predictions of blush coverage pre-harvest provides improved information to growers, allowing them to confidently make appropriate management strategy decisions (e.g. summer pruning, defoliation) in a timely manner for optimal red-colour development and blush coverage. In addition, early data on the expected blush coverage at harvest has the potential to inform the supply chain and direct the produce to the most profitable market.
To the best of the research team’s knowledge, this work is the first to estimate and forecast blush coverage in modern pear cultivars. Agriculture Victoria is currently conducting research on determining relationships between yield, fruit quality and tree geometry parameters that can drive precision management strategies through the PIPS3 Program’s AP19005 project.
This article was written by Alessio Scalisi, Lexie McClymont and Ian Goodwin from Agriculture Victoria. It was first published in the Autumn 2023 edition of AFG.
Further information
For videos on the Green Atlas Cartographer calibration and validation research and outcomes undertaken both through the AP19005 and AP19003 projects, head to the PIPS3 Program resources webpage.
Acknowledgements
The PIPS3 Program’s Developing smarter and sustainable pear orchards to maximise fruit quality, yield and labour efficiency (AP19005) project is funded by Hort Innovation, using the apple and pear research and development levy, contributions from the Australian Government and co-investment from Agriculture Victoria. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.
We gratefully acknowledge Matthew Lenne for granting access to Calimna Orchard, Ardmona, Victoria.
