Reduction of Early Fruit Abscission by Main-branch-girdling in Macadamia Is Related to the Favorable Status of Carbohydrates and Endogenous Hormones

Fruit abscission occurring severely in the early fruit development affects macadamia yield. Developing effective methods to improve fruit retention is a priority for macadamia cultivation and production. Girdling is an important horticultural practice that has been widely used to increase fruit yield. Previous studies have shown that girdling fails to increase macadamia yield despite enhancing the early fruit set, but few have examined the effect of girdling on its related physiological mechanism. The objective of this study was to investigate the effects of main-branch girdling (MBG) on early fruit retention and also on the levels of carbohydrates and endogenous hormones in the leaves, bearing shoots and fruit of macadamia. Herein, MBG was performed at fruit set using a single-blade knife on 9-year-old macadamia trees (Macadamia integrifolia). Results showed that MBG significantly reduced young fruit drop, concurrent with significant increases in the contents of starch in both the leaves and the bearing shoots and in glucose, fructose, and sucrose levels in the husk and seed. It was suggested that the availability of carbohydrate for fruit retention was improved by MBG. Additionally, MBG increased indole-3-acetic acid (IAA), gibberellin (GA3), and zeatin-riboside (ZR, a type of cytokinin) concentrations and decreased abscisic acid (ABA) contents in the husk and the seed, indicating that MBG reduced the early fruit drop by modifying the balance of endogenous hormones. Therefore, a positive interplay between carbohydrates and endogenous hormones induced by MBG was involved in the reduction of early fruit abscission in macadamia.

Morphology and Economic Value of Macadamia (Macadamia integrifolia Maiden and Betche)

Macadamia has a scientific name Macadamia integrifolia Maiden and Betche from the Proteaceae family. The Macadamia plant habitat is in highland areas with an altitude of 1000 masl with a temperature of ≤ 32˚C. Macadamia plants are perennials with tough stems, and the branching is visible (monopodial). The purpose of this study was to determine the morphological characteristics of Macadamia plants and their economic value. The research was conducted at PTPN XII Sempol Plantation, Bondowoso with descriptive-qualitative method. The results of morphological observations showed that macadamia fruit is a dry fruit, indehiscent (when ripe the skin/shell does not break), similar to the type of achene fruit but the shell is thick and hard. Woody stems (lignosus) with monopodial branching type, incomplete leaves consisting of stalks and leaf blades, leaf blades are oblong-elongated, incised independently, pinnate leaf bones, phyllotaxis opposite crosswise. Macadamia trees can produce round fruit of about 20-70 kg per year with a monthly profit of Rp. 8,905,500. The economic potential of the Macadamia plant is very promising, as evidenced by the ongoing import of peeled macadamia with a volume of 6,862 kilograms worth US$ 145,100 (approximately Rp 1.9 billion) or Rp 291,405.29 per kilogram.

Macadamia Volatiles Affect the Attraction of the Moth Gymnandrosoma Aurantianum to (E)-8-Dodecenyl Acetate the Main Component of its Sex Pheromone

The macadamia nut borer moth Gymnandrosoma aurantianum, is the main pest of macadamia (Macadamia integrifolia) in Central America. This study investigates the effect of the host (M. integrifolia) on attraction of G. aurantianum to its sex pheromone. Y-Tube bioassays showed that females G. aurantianum were attracted to volatiles from M. integrifolia leaves and flowers, while males responded to volatiles from flowers. Both sexes had significantly different electroantennographic responses (EAG) to the extracts of volatiles from flowers, fruits and leaves and (E)-8-dodecenyl acetate (main component of the sex pheromone of G. aurantianum). Females G. aurantianum exhibited electroantennographic responses by CG-EAD to phenylacetaldehyde, (1Z)-3-methylbutanal oxime and (E)-β-ocimene, while the males showed antennal activity in response to phenylacetaldehyde, (1E)-3-methylbutanal oxime, (1Z)-3-methylbutanal oxime, present in the extracts of M. integrifolia. The EAG dose-response with ocimene (mix of isomers) showed that female antennal activity increases as the dose increases, while with males, the highest dose elicited a response that was significantly different from the control. In field tests, the mixture (ocimene/(E)-8-dodecenyl acetate) with the proportion of 10:1 was the treatment that captured the highest number of males and females. Also, we observed that the lowest number of male captures was obtained with the proportion of 1:1, compared to the traps baited with only (E)-8-dodecenyl acetate. These results suggest that the binary mixture of ocimene plus (E)-8-dodecenyl acetate in a proportion of 10:1 could be an option for monitoring this pest because we obtained captures of both sexes.

Extracts of Different Organs of Macadamia Nut Tree (Macadamia Integrifolia) Ameliorate Oxidative Damage in D-Galactose Accelerated Aging Model in Rats

Macadamia nut tree, Macadamia integrifolia (Maiden & Betche), is cultivated for the production of the edible macadamia nuts, which are a good source of monounsaturated fatty acids. We investigated the effect of ethanolic extracts of leaves, nuts, and nutshells of macadamia in D-galactose accelerated aging model in rats. Administration of D-galactose (150 mg/kg) in rats for 60 days resulted in impairment of cognitive function and motor coordination and caused an increase in oxidative stress and deterioration of liver and kidney functions. Macadamia nut extract ameliorated cognitive impairment induced by D-galactose as inferred from Morris water maze test and balance test using rotarod. Also, nut extract was superior to leaves and shell extract in reducing serum levels of malondialdehyde (50%), alanine transaminase (63%), aspartate transaminase (63%), total bilirubin (24%), creatinine (38%), and urea (16%) compared to animals that received no treatment. Chemical analysis showed that macadamia nut extract has a high percentage of oleic acid (81%) followed by palmitoleic acid (6.9%). This study encourages further investigation of the health benefits of macadamia nuts and the underlying mechanism of these effects.

Shoot initiation for Macadamia integrifolia explant with tissue culture technique

Macadamia nuts are grown in subtropical and tropical regions and endemic species in Greenland that can be commercially developed in Indonesia. Macadamia’s generative propagation tends to have problems in its seed stock. It often experiences obstacles in field seed stock, and the production requires a long time because it has a thick shell (pericarp). Macadamia initiation needs technology to prevent extinction. One of the propagation is through the technique culture in vitro. This research was conducted to determine the initial response of basic media and to know the response of Macadamia growth in vitro. This research used five media which are Media 1 (DKW with BAP 0.1 ppm, kinetin 0.1ppm), Media 2 (WPM with BAP 1 ppm), media 3 (DKW), media 4 (MS), media 5 (MS with BAP 0.5 ppm). The results showed that media 1 and 3 (DKW media) had a good response for leaf and shoot growth in macadamia explants.

Utilization of low plants peat brickets for macadamia (Macadamia integrifolia) planting

Currently, the use of organic materials as organic fertilizer has been widely used by farmers. The awareness of farmers to use organic fertilizers has made organic fertilizers increasingly difficult to obtain. Organic fertilizers from chicken, goat and cow farms have generally been ordered and purchased by certain farmers. Therefore, alternative uses of other organic fertilizers need attention. Lowland peat is quite widely available in Indonesia, especially in North Sumatra. Peatlands are spread from the east coast of Aceh Province to the east coast of the Riau Province border. This potential makes it possible for peat to be modified into alternative organic fertilizers. One of the disadvantages of organic fertilizers is the large volume and weight. To overcome this problem, peat is made into briquettes through a pressing process so that its volume can be reduced to 1/3 times its previous volume. In addition, the acidic nature of peat is also expected to be greatly reduced by wasting peat water content. After being made into briquettes, the briquettes are used as organic fertilizer treatment for planting macadamia plants in the field. The results showed that the provision of briquettes from peat could increase the growth of macadamia plants compared to control. However, giving briquettes at a dose of 0.5 kg was not significantly different from giving briquettes up to 1.5 kg.

Novel Botrytis and Cladosporium Species Associated with Flower Diseases of Macadamia in Australia

Macadamia (Macadamia integrifolia) is endemic to eastern Australia and produces an edible nut that is widely cultivated in commercial orchards globally. A survey of fungi associated with the grey and green mold symptoms of macadamia flowers found mostly species of Botrytis (Sclerotiniaceae, Leotiomycetes) and Cladosporium (Cladosporiaceae, Dothideomycetes). These isolates included B. cinerea, C. cladosporioides, and unidentified isolates. Amongst the unidentified isolates, one novel species of Botrytis and three novel species of Cladosporium were delimited and characterized by molecular phylogenetic analyses. The new species are Botrytis macadamiae, Cladosporium devikae, C. macadamiae, and C. proteacearum.

Neopestalotiopsis Species Associated with Flower Diseases of Macadamia integrifolia in Australia

Macadamia (Macadamia integrifolia) is native to eastern Australia and produces an edible nut that is extensively cultivated in commercial orchards in several countries. Little is known about the diversity of fungi associated with diseases of macadamia inflorescences. A survey of fungi associated with the dry flower disease of macadamia detected several isolates of Neopestalotiopsis (Pestalotiopsidaceae, Sordariomycetes). Five new species of Neopestalotiopsis were identified based on molecular phylogenetic analyses of concatenated gene sequences of the internal transcribed spacer (ITS), β-tubulin (TUB), and the translation elongation factor 1-alpha (TEF1α). The new species are named Neopestalotiopsis drenthii, N. maddoxii, N. olumideae, N. vheenae, and N. zakeelii, and are described by molecular, morphological, and cultural characteristics. The ecology of the isolates and their pathogenic, saprophytic, or commensal ability were not determined.