Hyperspectral imaging for estimating leaf, flower, and fruit macronutrient concentrations and predicting strawberry yields.

Managing the nutritional status of strawberry plants is critical for optimizing yield. This study evaluated the potential of hyperspectral imaging (400-1,000 nm) to estimate nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) concentrations in strawberry leaves, flowers, unripe fruit, and ripe fruit and to predict plant yield. Partial least squares regression (PLSR) models were developed to estimate nutrient concentrations. The determination coefficient of prediction (R2P) and ratio of performance to deviation (RPD) were used to evaluate prediction accuracy, which often proved to be greater for leaves, flowers, and unripe fruit than for ripe fruit. The prediction accuracies for N concentration were R2P = 0.64, 0.60, 0.81, and 0.30, and RPD = 1.64, 1.59, 2.64, and 1.31, for leaves, flowers, unripe fruit, and ripe fruit, respectively. Prediction accuracies for Ca concentrations were R2P = 0.70, 0.62, 0.61, and 0.03, and RPD = 1.77, 1.63, 1.60, and 1.15, for the same respective plant parts. Yield and fruit mass only had significant linear relationships with the Difference Vegetation Index (R2 = 0.256 and 0.266, respectively) among the eleven vegetation indices tested. Hyperspectral imaging showed potential for estimating nutrient status in strawberry crops. This technology will assist growers to make rapid nutrient-management decisions, allowing for optimal yield and quality.

Hyperspectral Imaging of Adaxial and Abaxial Leaf Surfaces as a Predictor of Macadamia Crop Nutrition.

Tree crop yield is highly dependent on fertiliser inputs, which are often guided by the assessment of foliar nutrient levels. Traditional methods for nutrient analysis are time-consuming but hyperspectral imaging has potential for rapid nutrient assessment. Hyperspectral imaging has generally been performed using the adaxial surface of leaves although the predictive performance of spectral data has rarely been compared between adaxial and abaxial surfaces of tree leaves. We aimed to evaluate the capacity of laboratory-based hyperspectral imaging (400-1000 nm wavelengths) to predict the nutrient concentrations in macadamia leaves. We also aimed to compare the prediction accuracy from adaxial and abaxial leaf surfaces. We sampled leaves from 30 macadamia trees at 0, 6, 10 and 26 weeks after flowering and captured hyperspectral images of their adaxial and abaxial surfaces. Partial least squares regression (PLSR) models were developed to predict foliar nutrient concentrations. Coefficients of determination (R2P) and ratios of prediction to deviation (RPDs) were used to evaluate prediction accuracy. The models reliably predicted foliar nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), copper (Cu), manganese (Mn), sulphur (S) and zinc (Zn) concentrations. The best-fit models generally predicted nutrient concentrations from spectral data of the adaxial surface (e.g., N: R2P = 0.55, RPD = 1.52; P: R2P = 0.77, RPD = 2.11; K: R2P = 0.77, RPD = 2.12; Ca: R2P = 0.75, RPD = 2.04). Hyperspectral imaging showed great potential for predicting nutrient status. Rapid nutrient assessment through hyperspectral imaging could aid growers to increase orchard productivity by managing fertiliser inputs in a more-timely fashion.

High self-paternity levels and effects of fertilised-seed number on size of strawberry fruit.

Cross-pollination can increase fruit production in both self-incompatible and self-compatible fruit crops. However, it is often unclear what proportions of the fruit crop result from cross-pollination. We quantified the proportion of cross-pollinated seeds and the proportion of fertilised seeds in two strawberry cultivars, Red Rhapsody and Sundrench, at increasing distances from a cross-pollen source. We assessed whether fully self-pollinated fruit and partly cross-pollinated fruit differed in fruit size, colour, firmness, Brix and acidity. We also assessed whether fruit size and quality were affected by the number or percentage of fertilised seeds. Almost all seeds of both cultivars resulted from self-pollination (~98%), even at only 1 m from a cross-pollen source. Distance from a cross-pollen source did not affect the proportion of partly cross-pollinated fruit or the proportion of cross-pollinated seeds per fruit. The mass and diameter of fully self-pollinated Sundrench fruit, and the redness and Brix of fully self-pollinated Red Rhapsody fruit, were higher than partly cross-pollinated fruit. Fruit mass, length and diameter increased, and acidity decreased, with increasing numbers of fertilised seeds in both cultivars. Fruit mass also increased with the percentage of fertilised seeds. Our results show that cross-pollination was not required for Red Rhapsody and Sundrench fruit production, and that cross-pollination was a rare occurrence even close to cross pollen source. Self-pollen deposition on stigmas is required to maximise the number of fertilised seeds, and consequently fruit size and quality. Our research indicates that bees improve strawberry fruit size by increasing the number of stigmas that receive pollen. Our results suggest that placing bee hives on strawberry farms during flowering and establishing nearby pollinator habitat to support wild pollinators could improve strawberry yield and fruit quality.

Biomass and mineral nutrient partitioning among self-pollinated and cross-pollinated fruit on the same strawberry plant.

Pollen-parent effects on fruit size and quality have been found previously among competing self-pollinated and cross-pollinated fruit on the same Redlands Joy strawberry plant. These effects occur independently of the percentage of fertilized seeds on the fruit, but the expression of these effects on fruit size and some aspects of quality are greatest when calcium is in shortest supply. Here, we aimed to clarify at what developmental stages the self-pollinated and cross-pollinated fruit diverge in size and quality and whether differences between self-pollinated and cross-pollinated fruit are due to early differences in nutrient accumulation. Fruit were harvested at 1, 2 and 3 weeks after hand-pollination and at full ripeness, approximately 4 weeks after hand-pollination. We measured fruit mass, length, diameter, colour, and the concentrations of aluminium, boron, calcium, copper, iron, nitrogen, magnesium, manganese, sodium, phospho-rous, potassium and zinc. Temporary increases in fruit mass, length or diameter due to cross-pollination were evident at 1 or 2 weeks after pollination. Consistent increases in size and skin darkness from cross-pollination emerged in the final week of fruit development. We found little evidence that self-pollinated and cross-pollinated fruit differed in mineral nutrient accumulation at any stage of fruit development. The results demonstrate that cross-pollination effects on strawberry fruit size are evident briefly during early fruit growth but emerge mainly during the final week of fruit development. The effects of cross-pollination on fruit size are not the result of early differences in mineral nutrient accumulation between self-pollinated and cross-pollinated fruit.

Pollen limitation and xenia effects in a cultivated mass-flowering tree, Macadamia integrifolia (Proteaceae).

BACKGROUND AND AIMS: Pollen limitation is most prevalent among bee-pollinated plants, self-incompatible plants and tropical plants. However, we have very little understanding of the extent to which pollen limitation affects fruit set in mass-flowering trees despite tree crops accounting for at least 600 million tons of the 9200 million tons of annual global food production. METHODS: We determined the extent of pollen limitation in a bee-pollinated, partially self-incompatible, subtropical tree by hand cross-pollinating the majority of flowers on mass-flowering macadamia (Macadamia integrifolia) trees that produce about 200 000-400 000 flowers. We measured tree yield and kernel quality and estimated final fruit set. We genotyped individual kernels by MassARRAY to determine levels of outcrossing in orchards and assess paternity effects on nut quality. KEY RESULTS: Macadamia trees were pollen-limited. Supplementary cross-pollination increased nut-in-shell yield, kernel yield and fruit set by as much as 97, 109 and 92 %, respectively. The extent of pollen limitation depended upon the proximity of experimental trees to trees of another cultivar because macadamia trees were highly outcrossing. Between 84 and 100 % of fruit arose from cross-pollination, even at 200 m (25 rows) from orchard blocks of another cultivar. Large variations in nut-in-shell mass, kernel mass, kernel recovery and kernel oil concentration were related to differences in fruit paternity, including between self-pollinated and cross-pollinated fruit, thus demonstrating pollen-parent effects on fruit quality (i.e. xenia). CONCLUSIONS: This study is the first to demonstrate pollen limitation in a mass-flowering tree. Improved pollination led to increased kernel yield of 0.31-0.59 tons ha-1, which equates currently to higher farm-gate income of approximately $US3720-$US7080 ha-1. The heavy reliance of macadamia flowers on cross-pollination and the strong xenia effects on kernel mass demonstrate the high value that pollination services can provide to food production.

SNP markers reveal relationships between fruit paternity, fruit quality and distance from a cross-pollen source in avocado orchards.

Cross-pollination can improve fruit yield, fruit size and nutritional quality of many food crops. However, we rarely understand what proportions of the crop result from self- or cross-pollination, how cross-pollination affects crop quality, and how far pollen is transported by pollinators. Management strategies to improve pollination services are consequently not optimal for many crops. We utilised a series of SNP markers, unique for each cultivar of avocado, to quantify proportions of self- and cross-paternity in fruit of Hass avocado at increasing distances from cross-pollen sources. We assessed whether distance from a cross-pollen source determined the proportions of self-pollinated and cross-pollinated fruit, and evaluated how self- and cross-paternity affected fruit size and nutritional quality. Avocado fruit production resulted from both self- and cross-pollination in cultivar Hass in Queensland, Australia. Cross-pollination levels decreased with increasing distance from a cross-pollen source, from 63% in the row adjacent to another cultivar to 25% in the middle of a single-cultivar block, suggesting that pollen transport was limited across orchard rows. Limited pollen transport did not affect fruit size or quality in Hass avocados as xenia effects of a Shepard polliniser on size and nutritional quality were minor.

Cross-pollination affects fruit colour, acidity, firmness and shelf life of self-compatible strawberry.

Cross-pollination affects the fruit characteristics of many crops but the effects of cross-pollination on fruit quality of strawberry (Fragaria × ananassa Duch.) are poorly known. This study determined how cross-pollination affects fruit quality of the strawberry cultivar, Redlands Joy, under controlled environment conditions. Plants were allocated to one of four treatments, with all flowers on each plant receiving either: (1) unassisted self-pollination (Autogamy); (2) hand-pollination with Redlands Joy pollen (Self); (3) hand-pollination with cross-pollen from a small-fruited cultivar (Sugarbaby); or (4) hand-pollination with cross-pollen from a large-fruited cultivar (Rubygem). Cross-pollination did not significantly affect plant yield or fruit mass, size, shape, firmness or shelf life. However, cross-pollination affected fruit colour and taste attributes. Cross-pollinated fruit were 3%-5% darker than self-pollinated fruit. They also had 26%-34% lower acidity and 43%-58% higher Brix:acid ratio. Cross-pollination by Sugarbaby increased fruit P, K, Ca, Fe and Mn, but decreased B, Cu and Zn, concentrations. Cross-pollination by Rubygem increased fruit Mn, but decreased K and Na, concentrations and reduced shelf life. Fruit mass, length, diameter and firmness within all treatments increased with increasing numbers of fertilized seeds per fruit. Hand self-pollinated fruit had a higher percentage of fertilized seeds than fruit arising from autogamy and they were also darker, redder, firmer, and had a longer shelf life, higher protein concentration, and lower Al and Na concentrations. The results indicate that strawberry fruit quality can be affected by both the source of pollen and the number of stigmas pollinated.

Single-nucleotide polymorphisms that uniquely identify cultivars of avocado (Persea americana).

PREMISE: Progeny of avocado (Persea americana) are highly variable due to high levels of heterozygosity. Breeding programs need molecular resources to allow the assessment of genetic differences and the selection of genotypes. Polymorphisms that uniquely identify different avocado cultivars provide a valuable tool to accelerate avocado research and development, including, for example, genotype selection. METHODS: A double-digest restriction site-associated DNA sequencing (ddRADseq) approach was used to screen 10 avocado cultivars for single-nucleotide polymorphisms (SNPs). The fragments were size selected with Blue Pippin and PCR using universal Illumina primers, and catalog tags were then created with de novo alignment using Stacks software. Catalog tags were tabulated and filtered to identify alleles unique to each cultivar. RESULTS: A total of 104 million sequences were collected, and 52 homozygous SNPs were identified that uniquely distinguished nine avocado cultivars. The cultivars Carmen Hass and Hass have a strong genetic similarity and no homozygous SNPs distinguishing these cultivars could be identified; therefore, both cultivars were grouped together. DISCUSSION: The resource described here for cultivars of P. americana presents a new and significant molecular resource that can enable targeted genotype selection, paternity analysis, germplasm genotyping, pollination dynamics investigation, and crop improvement.

Relationships between Nut Size, Kernel Quality, Nutritional Composition and Levels of Outcrossing in Three Macadamia Cultivars.

Tree nuts play an important role in healthy diets, but their economic value and nutritional quality may be affected by their size and paternity. We assessed relationships between nut size and kernel recovery, the incidence of whole kernels, fatty acid composition and mineral nutrient concentrations in three macadamia cultivars, "Daddow", "816" and "A4". We determined to what extent differences in nut size and quality were the result of different levels of cross- or self-paternity. Small nuts of all cultivars had lower kernel recovery than large nuts, and small nuts provided lower incidence of whole kernels in "Daddow" and "A4". Small kernels had a lower relative abundance of the saturated fatty acid, palmitic acid, in all cultivars and higher relative abundance of the unsaturated fatty acid, oleic acid, in "Daddow" and "A4". Small kernels had higher concentrations of many essential nutrients such as nitrogen and calcium, although potassium concentrations were lower in small kernels. Most nuts arose from cross-pollination. Therefore, nut size and kernel quality were not related to different levels of cross- and self-paternity. Identified cross-paternity was 88%, 78% and 90%, and identified self-paternity was 3%, 2% and 0%, for "Daddow", "816" and "A4", respectively. Small macadamia kernels are at least as nutritious as large macadamia kernels. High levels of cross-paternity confirmed that many macadamia cultivars are predominantly outcrossing. Macadamia growers may need to closely inter-plant cultivars and manage beehives to maximise cross-pollination.

The effects of tree spacing regime and tree species composition on mineral nutrient composition of cocoa beans and canarium nuts in 8-year-old cocoa plantations.

The selection of shade trees with appropriate spacing is important for minimising their impact on nutrient accumulation by understorey cash crops in agroforestry systems. Cocoa trees may be intercropped with overstorey legume or non-legume shade trees. A legume tree and/or a non-legume timber tree with edible kernels (Gliricidia sepium and Canarium indicum, respectively) are used as shade trees in cocoa plantations particularly in Papua New Guinea. This study explored the nutrient concentrations of cocoa beans in response to both tree-shade species and shade-tree spacing regime. The study also investigated the extent to which C. indicum tree spacing altered the nutrient concentrations of canarium kernels. G. sepium trees in the study had a final spacing of 12 m × 12 m while the spacing regimes of either 8 m × 8 m or 8 m × 16 m used for C. indicum. The calcium (Ca) concentrations of cocoa beans did not differ significantly between plants located next to G. sepium and plants located next to C. indicum. Cocoa beans next to C. indicum trees with spacing of 8 m × 16 m had higher potassium (K) concentrations than those next to G. sepium trees. However, phosphorus (P) concentrations of cocoa beans next to C. indicum trees with spacing of 8 m × 8 m or next to G. sepium trees were significantly higher than those next to C. indicum trees with spacing of 8 m × 16 m. The K concentrations in cocoa beans and soil were not correlated nor were the P concentrations in cocoa beans and soil. Correlations between nutrients in leaves and cocoa beans, or between leaves and canarium kernels, were not strong. Our results suggest that cocoa and canarium trees can be intercropped successfully, and that they do not compete for soil nutrients.

Nutrient uptake by constructed floating wetland plants during the construction phase of an urban residential development.

This study investigated plant growth, nutrient partitioning and total nutrient uptake by tall sedge (Carex appressa) plants in two large-scale Constructed Floating Wetlands (CFW1 and CFW2). These CFWs were installed to treat stormwater runoff discharging into a newly-constructed 2.6-ha lake during the construction phase of a 45-ha residential development. Nutrient concentrations of C. appressa shoot above the mat, biomass within the mat, and roots below the mat were analysed 0, 12 and 16 months after planting. Extensive root growth was evident after 12 and 16 months. Some nutrients (nitrogen, phosphorus, sulphur) were distributed almost evenly among the above-, within-, and below-mat components, while others (aluminium, copper, iron, manganese) were concentrated in or on the roots. Given the low concentrations of nutrients within the water column, large amounts of nutrients were removed from stormwater by the plants. Total nitrogen uptake was 20.20 ±â€¯2.88 kg in CFW1 and 15.00 ±â€¯2.07 kg in CFW2 over the 16-month study period. Total potassium uptake was 12.59 ±â€¯1.64 kg in CFW1 and 7.20 ±â€¯1.56 kg in CFW2. Phosphorus uptake was low as a consequence of low phosphorus availability in the water. High aluminium, iron and manganese concentrations were found in the roots, demonstrating that C. appressa removed and sequestered large quantities of these water pollutants from urban stormwater runoff. For example, total aluminium uptake was 7.82 ±â€¯1.73 kg in CFW1 and 5.62 ±â€¯0.75 kg in CFW2. This study demonstrated multiple benefits of CFWs for stormwater treatment in the early stages of an urban development.

Antibacterial Properties of Flavonoids from Kino of the Eucalypt Tree, Corymbia torelliana.

Traditional medicine and ecological cues can both help to reveal bioactive natural compounds. Indigenous Australians have long used kino from trunks of the eucalypt tree, Corymbia citriodora, in traditional medicine. A closely related eucalypt, C. torelliana, produces a fruit resin with antimicrobial properties that is highly attractive to stingless bees. We tested the antimicrobial activity of extracts from kino of C. citriodora, C. torelliana × C. citriodora, and C. torelliana against three Gram-negative and two Gram-positive bacteria and the unicellular fungus, Candida albicans. All extracts were active against all microbes, with the highest activity observed against P. aeruginosa. We tested the activity of seven flavonoids from the kino of C. torelliana against P. aeruginosa and S. aureus. All flavonoids were active against P. aeruginosa, and one compound, (+)-(2S)-4',5,7-trihydroxy-6-methylflavanone, was active against S. aureus. Another compound, 4',5,7-trihydroxy-6,8-dimethylflavanone, greatly increased biofilm formation by both P. aeruginosa and S. aureus. The presence or absence of methyl groups at positions 6 and 8 in the flavonoid A ring determined their anti-Staphylococcus and biofilm-stimulating activity. One of the most abundant and active compounds, 3,4',5,7-tetrahydroxyflavanone, was tested further against P. aeruginosa and was found to be bacteriostatic at its minimum inhibitory concentration of 200 µg/mL. This flavanonol reduced adhesion of P. aeruginosa cells while inducing no cytotoxic effects in Vero cells. This study demonstrated the antimicrobial properties of flavonoids in eucalypt kino and highlighted that traditional medicinal knowledge and ecological cues can reveal valuable natural compounds.

Chemical constituents of kino extract from Corymbia torelliana.

Seven flavanones were identified from kino exudate of Corymbia torelliana by spectroscopic and spectrometric methods including UV, 1D and 2D NMR and UPLC-HR-MS. The study identified seven molecules, namely 3,4',5,7-tetrahydroxyflavanone (1), 3',4',5,7-tetrahydroxyflavanone (2), 4',5,7-trihydroxyflavanone (3), 3,4',5-trihydroxy-7-methoxyflavanone (4), (+)-(2S)-4',5,7-trihydroxy-6-methylflavanone (5), 4',5,7-trihydroxy-6,8-dimethylflavanone (6) and 4',5-dihydroxy-7-methoxyflavanone (7) from this eucalypt species. This is the first report of these natural products from C. torelliana kino exudate.