Macadamia Trees Research Articles

Variation in susceptibility among macadamia genotypes and species to Phytophthora root decay caused by Phytophthora cinnamomi

Phytophthora cinnamomi is a major pathogen of cultivated macadamia (Macadamia integrifolia, Macadamia tetraphylla and their hybrids) worldwide. The susceptibility of the two non-edible Macadamia species (Macadamia ternifolia and Macadamia jansenii) to P. cinnamomi is not well-understood. Commercial macadamia trees are established on grafted seedling (seed propagation) or own-rooted cutting (vegetative propagation) rootstocks of hybrids of the cultivated species. There is little information to support the preferential use of rootstock propagated by either seedling or own-rooted cutting methods in macadamia. In this study we assessed roots of macadamia plants of the four species and their hybrids, derived from the two methods of propagation, for their susceptibility to P. cinnamomi infection. The roots of inoculated plant from which P. cinnamomi was recovered showed blackening symptoms. The non-cultivated species, M. ternifolia and M. jansenii and their hybrids were the most susceptible germplasm compared with M. tetraphylla and M. integrifolia. Of these two species, M. tetraphylla was less susceptible than M. integrifolia. Significant differences were observed among the accessions of their hybrids. A strong association (R2 > 0.75) was recorded between symptomatic roots and disease severity. Root density reduced with increasing disease severity rating in both own-rooted cuttings (R2 = 0.65) and germinated seedlings (R2 = 0.55). P. cinnamomi severity data were not significantly (P > 0.05) different between the two methods of plant propagation. The significance of this study to macadamia breeding and selection of disease resistant rootstocks is discussed.

A STUDY OF PYROLYSIS OF MACADAMIA NUT SHELL: PARAMETRIC SENSITIVITY ANALYSIS OF THE IPR MODEL

The macadamia tree is known for producing fruit high in fats, enclosed in very hard woody shells. Macadamia nut shell, considered as a by-product from macadamia nut processing, may be a suitable option for pyrolysis. These residues are constituted of cellulose, hemicellulose, lignin and extractives. The Independent Parallel Reaction (IPR) Model has been applied in this work to study the pyrolysis of macadamia nut shell from thermogravimetric experiments. The kinetic parameters and mass fraction of each component were estimated using the Differential Evolution Algorithm. The influence of the model parameters was also analyzed by means of sensitivity studies. The results showed that the decomposition of the macadamia nut shell is more sensitive to the parameters related to the decomposition of lignin. The results of sensitivity analysis also showed that the activation energy affects the total biomass conversion more strongly than the other parameters and the contribution of extractives in the IPR model is as important as the hemicellulose.

Variation of cutting rooting ability in cultivated and wild species ofMacadamia

In Australia, macadamia trees are commonly propagated by germinating rootstock seed and grafting when seedlings reach a suitable size. The production of grafted trees is a protracted and complex process, however, propagation of macadamia via cuttings represents a simpler and faster method of multiplication. Macadamias have traditionally proven difficult to propagate from cuttings, and while recent developments in the process have improved success rates, substantial variation in rooting ability between cultivars and species has been reported. The cultivar 'Beaumont' (Macadamia integrifolia × M. tetraphylla) is commonly propagated by cutting for use as a rootstock, and is relatively easy to strike while other cultivars are more difficult. There is speculation that Hawaiian cultivars are more difficult to strike from cuttings than Australian cultivars due to species and genetic composition. In this experiment, cuttings of 32 genotypes were evaluated for rooting ability. Each genotype's species profile was estimated using historical data, and used to determine species effects on survival (percentage) and rooting ability (rating 0-2). M. jansenii (100%), M. tetraphylla (84%) and M. integrifolia/tetraphylla hybrids (79%) had the highest success rates while M. integrifolia (54%) and M. ternifolia (43%) had the lowest survival. Rooting ability of M. jansenii (1.75) was significantly higher than M. ternifolia (0.49) but not significantly higher than M. tetraphylla × M. integrifolia with (1.09), M. tetraphylla (1.03) or M. integrifolia (0.88).

Half-topping 'A4' macadamia trees has a markedly different effect on yield than full-topping

Mechanically hedging the tops of macadamia trees to control tree size is referred to as topping. Topping the entire upper canopy causes a substantial reduction in yield and is not a recommended industry practice. Here we compare topping just half the upper canopy with full-topping, and with control trees that were not pruned, to test whether half-topping is a more acceptable means of size control, with less of a yield penalty. We used macadamia cultivar ‘A4’ as the subject for the study. The trees were topped horizontally at anthesis. Full-topping reduced yields by 78% in the first year and 63% in the second year compared with the control trees. By the end of the second year the height of the fully-topped trees was approximately the same as that of the control trees. In contrast, topping just the western half of the upper canopy resulted in little yield penalty. Yields were reduced non-significantly by 14% in the first year, and negligibly in the second year, compared with the control trees; and by the end of the second year, the regrowth on the topped halves of the trees was only two-thirds the height of that on the full-topped trees. The results are encouraging because topping is simple and cheap, and would be an attractive tree size control option for growers at the yield penalty described here for the half-topped treatment.

First Record ofEllimenistes laesicollis(Coleoptera: Curculionidae) as a Garden Pest in the Western Cape, South Africa

Ellimenistes laesicollis Fahraeus (Coleoptera: Curculionidae: Entiminae: Embrithini) is a rather small (4-5 mm long), grey weevil (Fig. 1) that was described in 1871 from material collected by A.J.A. Wahlberg during his visit to southern Africa (1838-1845). It remained unnoticed for many years until Keetch (1973) recorded it as a pest of arabica coffee (Coffee arabica) in KwaZulu-Natal (KZN) and called it the grey coffee snout beetle. The adult beetles were found to feed on the peduncle (stalk) of young coffee fruit which abort as a result, causing yield losses of up to 40%. The beetles also eat the soft succulent suckers, which snap. They eat cavities into green berries and into the stalk of more mature fruit, causing the fruit to fall, and damage flowers and leaves. They mainly attack young and newly planted coffee, but can also damage mature trees (Keetch et al. 1974;Annecke & Moran 1982). Keetch (1973) found it onvarious other plants such as Bidens pilosa (blackjack), water grass (Cyperus sp.), Grevillea robusta (silky oak) and sugarcane; he mentions that it is apparently of no economic significance on sugarcane. Schoeman (2001), however, called it the sugar cane snout beetle and mentioned that he had observed it feeding on the epidermis of banana in the Eshowe region, KZN, where it led to severe downgrading of the fruit. Schoeman (2009, 2015) recorded it as a pest of macadamia. In 2007 and 2008 he observed substantial damage on recently planted macadamia trees in the Stanger (now KwaDukuza) region of KZN and large infestations on mature trees in the Empangeni area of the same province. He also observed it in 2008 on macadamia in the Chipinge area of eastern Zimbabwe. It is also listed as a defoliator pest during the establishment of wattle and eucalypt seedlings (Govender 2002, 2007) and as a pest of tea (Annecke & Moran 1982).

Empirical models to predict LAI and aboveground biomass of Coffea arabica under full sun and shaded plantation: a case study of South of Minas Gerais, Brazil

Leaf area index (LAI) and above ground biomass (AGB) are two parameters that are difficult to measure but very useful. In this paper we investigated the relationship between coffee biophysical properties and LAI and AGB in two coffee production systems: full sun (FS) and shaded with macadamia nuts (SH). The paper proposes an empirical relationship for calculating coffee AGB and coffee LAI which avoids destructive methods, using simple field measurements and agrometeorological data. Here, we reported that LAI is related to canopy structure but subject to strong seasonal variations, which can be identified using water requirements satisfaction index (WRSI). Coffee LAI answers to the decreased WRSI with 1 month lag (WRSI-1) and LAI values decreases more for FS systems than for SH systems during dry periods. The best empirical model to predict LAI for FS coffee production system was based on canopy height (ch) and WRSI-1 value. For SH systems, the best model used ch, WRSI-1 and the height of the first pair of branches. Coffee AGB values were measured using destructive analyses and an empirical equation was developed. Both coffee production systems stocked carbon, whereas the SH system stocked an increased carbon amount provided by the macadamia trees that contributed with 15 % of the total carbon above ground. Both systems can be considered mitigation techniques since they are able to remove atmospheric carbon and stock it in the biomass, which has been largely proposed as a compensation mechanism for greenhouse gas emissions.

Irrigation and Intercropping with Macadamia Increase Initial Arabica Coffee Yield and Profitability

Although some regions of Brazil are considered suitable for Arabica coffee (Coffea arabica L.) cultivation under rainfed and full‐sun conditions, irrigation and afforestation, especially for species that generate an economic return, may be alternative methods for improving coffee crop performance, diversifying and maximizing income. However, it is unclear whether additive effects occur due to the joint use of these practices. Thus, an experiment was conducted over a 7‐yr period to evaluate the growth, yield, and profitability of Arabica coffee in monocropping and intercropping systems with macadamia (Macadamia integrifolia Maiden & Betche) under rainfed and drip‐irrigation regimes in southeastern Brazil. Monocropped coffee plants were planted with a spacing of 3.5 by 0.7 m (4082 plants ha−1). In the intercropping systems, the macadamia trees were planted at a spacing of 10.5 by 4.9 m (194 plants ha−1) and the coffee plants at a spacing of 3.5 by 0.7 m (3887 plants ha−1). Intercropping with macadamia increased the coffee yield by 10% under rainfed conditions. Drip irrigation promoted greater growth and increased the coffee and macadamia yields by 60 and 133%, respectively. In the monocropped coffee under rainfed conditions, the first five harvest years were not sufficient to pay for the investments. Interestingly, both irrigation and intercropping increased the economic benefits. Furthermore, the irrigated coffee intercropped with macadamia resulted in the greatest profitability after the first five harvests. Thus, this system is an interesting alternative for increasing the sustainability of the Arabica coffee crop in the initial cropping years.

ROLE OF TEMPERATURE AND ALTITUDE ON FLOWERING PERFORMANCES OF MACADAMIA NUT

The study aimed to observe the flowering of macadamia grown under different locations in northern Thailand. It is hoped that the success of macadamia growing would be an opium substitute crop as well as a reforestation tree in northern Thailand. Although introduced cultivars have adapted well and are grown widely from sea level to the top of mountains, the yield is still low compared to those reported in other countries. The role of microclimate as a factor influencing annual growth cycle should be clearly understood to further develop appropriate cultural practices. Fifteen uniform mature macadamia trees were selected from three sites with two types of microclimate characteristics; mountain ridge and valley at commercial plantations of Doi Tung Development Project in Chiang Rai, northern Thailand. Floral biology, fruiting and vegetative flushing characters were observed from limb at 1.5-2 m above ground level. Air temperature and light intensity, as microclimate parameters were recorded during 2007-2008. Mostly racemes and fruits set on two-year-old shoots. The fruiting shoots of trees located at mountain ridge had significantly shorter length than at the valley site. Seasonal new vegetative shoots at three sites flushed on the same period. Racemes of trees at mountain ridge bloomed earlier in late November; however, it was one month later for trees at valley site. Interestingly, the flower phenology at the valley site showed better performances with a shorter bloom period and higher floret numbers resulting in higher fruiting rate. Daily light intensity, minimum and average temperature of two microclimate types or three altitudes showed similar pattern. Nevertheless, maximum temperature during flowering at the valley site was lower. Thus, the amount of daily temperature interval occurring at lower level might cause the differences in flowering and yield performances. In addition, the flowering and fruit setting of rain-fed and irrigated sites were observed on ten mature trees at the ridge. It was found that trees in rain-fed site had two periods of flowering; the first in-season bloom was in January after annual nut harvesting started and the second bloom, a so-called off-season, was found later in October. The off-season bloom of macadamia trees grown in northern Thailand reflected their adaptability to Thai environment. Thus, it might be a good potential that is of benefit to further develop off-season macadamia nut production.

Ocorrência de plantas daninhas em cultivo consorciado de café e nogueira-macadâmia

A arborização pode beneficiar os cafezais, reduzindo a velocidade dos ventos e a amplitude térmica na cultura. É possível, ainda, que a diminuição na radiação incidente possa influenciar a população de plantas daninhas e diminuir a necessidade de seu controle. Objetivou-se, com este trabalho, avaliar a população e a distribuição de plantas daninhas, na cultura de café arábica consorciado com três cultivares de nogueira-macadâmia, seis anos após o plantio, em Dois Córregos (SP). Os tratamentos consistiram de esquema fatorial 3x3+1, ou seja, café consorciado com três cultivares de nogueira-macadâmia (HAES 816, IAC 4-20 e IAC 9-20) e três locais de amostragem das plantas daninhas no consórcio (na projeção da copa da nogueira-macadâmia, entre as projeções das copas da nogueira-macadâmia e na entrelinha solteira), além de um tratamento adicional (café solteiro). Foram avaliados a incidência e o controle de plantas daninhas, bem como a caracterização fitossociológica. No cultivo de café consorciado com nogueira-macadâmia, a ocorrência e o número de espécies de plantas daninhas foram menores que no cultivo de café solteiro. Na projeção da copa e entre as projeções das copas da nogueira-macadâmia, houve, em média, 82% de redução na ocorrência de plantas daninhas, em comparação ao café solteiro. A cultivar IAC 9-20, por apresentar copa mais alta e de maior diâmetro, foi mais eficiente na redução da ocorrência de plantas daninhas, no consórcio com café.

Phosphite and metalaxyl rejuvenate macadamia trees in decline caused by Phytophthora cinnamomi

Phytophthora cinnamomi is a significant pathogen of macadamia but little information on disease management exists. Through a series of glasshouse and field trials using different rates and modes of application of phosphite, this study provides data and information on effective application rates of phosphite for the control of macadamia tree decline caused by P. cinnamomi. We also determined the efficacy of bark spray application of phosphite and soil drench application of metalaxyl on recovery of declining macadamia trees. Overall, our results indicate that regardless of the method of application, biannual applications of phosphite during autumn and spring root flushes in macadamia are effective control options for tree decline. Phosphite applied as trunk injection resulted in relatively higher detection of phosphonic acid levels in the plant tissues compared to other methods of application, and the phytotoxic effect was also more severe than foliar spray application. Foliar and trunk spray application of phosphite or soil drench with metalaxyl-M resulted in consistent (R2 > 0.98) rejuvenation of diseased trees over 3 years compared to untreated control trees that continued to decline (y = 1 + 0.22ln(x); R² = 0.96). Phytotoxicity of phosphite on macadamia leaves occurred at relatively lower rates than indicated for other tree crops. The sensitivity of macadamia to phosphite relative to other tree crops is discussed.

First report of a ‘Candidatus Phytoplasma asteris’ isolate affecting a strawberry nursery in Cuba

Strawberry (Fragaria x ananassa) is traditionally multiplied in Cuba by vegetative propagation without phytosanitary certification. During November 2011, surveys for phytoplasma to strawberry nurseries revealed plants showing symptoms of leaf yellowing and reddening, fruit deformation and stunting in an orchard of ‘Ceiba del Agua’, Artemisa province (Fig. 1). Similar symptoms were previously described in strawberry associated with phytoplasma infections (Jomantiene et al., 3; Valiunas et al., 6). Leaves and midribs collected from symptom-bearing and symptomless plants were subjected to total DNA extraction (Murray & Thompson, 4). Total DNA was used as a template in a nested-PCR with generic primers targeting the phytoplasma 16S rRNA gene: P1/P7 (Deng & Hiruki, 1) and R16F2n/R16R2 (Gundersen & Lee, 2). R16F2n/R2 amplicons were purified, ligated in pGEM®-T Easy vector (Promega, Madison, WI, USA) and sequenced. The derived sequences were identified by comparison with phytoplasma reference sequences using BLAST (www.ncbi.nlm.nih.gov) and RFLP analysis (determined by comparing the digestion sites map for the endonucleases EcoRI, BfaI, HinfI, RsaI, AluI, MseI, HpaII and HaeIII using VECTOR NTI v.8.0 from Invitrogen, CA, USA). Phylogenetic trees were constructed using Mega 4.0. R16F2n/R2 amplicons of expected size (approx. 1200 bp) and similar to the reference control were amplified from 13/14 symptom-bearing plants. No amplification was yielded by symptomless plants (6/6). Two individual clones derived from four symptom-bearing plants were sequenced, and the partial consensus sequence of 1139 nt (GenBank Accession No. KC825053) exhibited 99% sequence identity with those of group 16SrI ‘Ca. Phytoplasma asteris’, closer to members of subgroup 16SrI-F, including the apricot chlorotic leaf roll-aster yellow phytoplasma, ACLR-AY (AY265211), aster yellows phytoplasma strain CVB (AY265212), Bajgah periwinkle little leaf phytoplasma (DQ266089), and macadamia phytoplasma (KC513772). Nucleotide comparison with strawberry phytoplasma sequences from Lithuania (DQ086423: Valiunas et al., 6) and USA (U96614, U96616: Jomantiene et al., 3) showed identities lower than 98%. RFLP profiles derived from the R16F2n/R2 amplicon sequence were identical to those of the subgroup 16SrI-F mentioned above used as reference. A phylogenetic tree based on the 16S rDNA sequence of the strawberry phytoplasma under study and those of reference sequences supported PCR and RFLP results, and confirmed that the phytoplasma is a member of the 16SrI ‘Ca. Phytoplasma asteris’ group, and possibly subgroup 16SrI-F (Fig. 2). This is the first report of a ‘Ca. Phytoplasma asteris’ isolate associated with symptoms in Cuban strawberry plants. Both RFLP and phylogeny analysis show the closest relationship between the strawberry phytoplasma (KC825053) and the previously phytoplasma identified from Cuban macadamia trees (Pérez-López et al., 5) in Artemisa province. This suggests complex epidemiological implications for the two ‘Ca. Phytoplasma asteris’ isolates in two different plant hosts within the same geographic location; indicating the possibility of significant risk of distributing possible phytoplasma-infected propagation material from strawberry nurseries to commercial strawberry fields. A more distant relationship was found between the Cuban strawberry phytoplasma sequence and those reported from strawberry in other countries, suggesting that this fruit crop supports the infection by a wide phytoplasma range. This research was supported by the Cuban Fruit Corporate Group (Grupo Empresarial Frutícola de Cuba, GEF) through national projects 0578 and 2004.

First report of a ‘Candidatus Phytoplasma asteris’ isolate affecting macadamia nut trees in Cuba

DNA was extracted from 0.5 g of leaf midribs of twelve macadamia plants collected (Murray & Thomsom, 1980), and used as a template for a nested PCR assay. Universal primer pairs that target the phytoplasma 16S rRNA gene, P1 (Deng & Hiruki, 1991) and P7 (Schneider et al., 1995) were used for the first reaction, and R16F2n/R16R2 (Gundersen & Lee, 1996) for the nested reaction. Nested PCR products of expected size (approximately 1250 bp) were obtained from ten symptom-bearing plants. PCR products were purified (Wizard SV Gel and PCR Clean-Up System, Promega, Madison, WI, USA), cloned (pGEMT-Easy Vector, Promega), and two individual clones per infected plant were sequenced using Macrogene Inc. Sequencing Service. The R16F2n/R16R2 sequences were subjected to in silico restriction fragment length polymorphism (RFLP) analysis with endonucleases AluI, BfaI, BstUI, HaeIII, HhaI, HinfI, HpaII, MseI and Tsp509 (pDRAW32 AcaClone Software, http://www.acaclone.com). Phylogenetic relationships were established between the macadamia phytoplasma and those of 16SrI and other phytoplasma groups (Mega 5.0, USA). The R16F2n/R16R2 sequences of phytoplasmas detected in the symptom-bearing samples were 100% identical to each other. The consensus sequence (1262 nt) of the macadamia phytoplasma was deposited in GenBank (Accession No. KC513772) and showed 99% of sequence identity with those of the 16SrI group ‘Candidatus Phytoplasma asteris’, including phytoplasma strains AY-CVB (AY265212), ACLR-AY (AY265211) and Baigah periwinkle little leaf phytoplasma (DQ266089), all members of subgroup 16SrI-F. The virtual RFLP profile of the macadamia phytoplasma was identical to those of the 16SrI-F subgroup, which suggests that the phytoplasma strain detected in Cuban macadamia trees may be a member of this subgroup. The results of sequence and RFLP analyses were confirmed by phylogeny (Fig. 2) since the macadamia phytoplasma grouped within the cluster corresponding to the 16SrI group, closely related to those of subgroup 16SrI-F. The group 16SrI was first recorded in Cuba in 1999 (Arocha et al., 1999) and since then in several other plant species. However, this is the first report of a phytoplasma of group 16SrI associated with symptoms in macadamia nut trees, a possible new host for 16SrI phytoplasmas. These results have a significant impact for Cuban agriculture since phytoplasma group 16SrI is well known by its widest plant host range and the most complex epidemiology worldwide, and macadamia may become an important future export crop for the Cuban fruit industry.

Historic Bauple Nut Tree Lost

In 2010, a tree that is part of Maryborough's history was lost. It was the parent of what has become one of the superior macadamia varieties widely planted in the Australian and international nut industry. This Bauple nut, Queensland nut or macadamia tree was given the name ‘Daddow’ and this is its story.

Pericarps retained in the tree canopy and stomatal abundance are components of resistance to husk spot caused by Pseudocercospora macadamiae in macadamia

Pseudocercospora macadamiae Beilharz, Mayers and Pascoe infects macadamia fruit via stomata causing husk spot disease. Information on the variability of fruit stomatal abundance, its association with diseased fruit pericarps (sticktights) that are retained in the tree canopy, and its influence on the husk spot intensity (incidence, severity and lesion number) among macadamia genotypes is lacking. We examined a total of 230 macadamia trees comprising 19 cultivars, 56 wild germplasm accessions and 40 breeding progeny, for the prevalence of sticktights and husk spot intensity over three production seasons. We observed a strong association between the prevalence of sticktights and disease intensity indicating its usefulness as a predictor of husk spot and as a useful phenotypic trait for husk spot resistance selection in breeding programmes. Similarly, stomatal abundance varied among macadamia genotypes, and a significant linear relationship (P < 0.001; 93%) was observed between fruit stomatal abundance and husk spot for all the macadamia genotypes analysed, confirming the utility of that trait for disease resistance screening. The genotypes were grouped into disease resistance groups. Correlations between fruit stomatal abundance, disease intensity and prevalence of sticktights revealed that the numbers of sticktights, and relative stomatal abundance were the main factors influencing the intensity of husk spot among macadamia genotypes. This is the first comprehensive study of natural variation of stomatal abundance in Macadamia species that reveals genetic variation, and provides relevant relationships with disease intensity and the prevalence of sticktights. The phenotypic plant traits indentified in this study may serve as selection tools for disease resistance screening in macadamia breeding programmes.

Effects of the ethylene inhibitor aminoethoxyvinylglycine (AVG) on fruit abscission and yield on pruned and unpruned macadamia trees

Macadamia, a subtropical evergreen tree, flowers profusely but sheds more than 98% of flowers and fruitlets within 10 weeks of anthesis. This premature fruit abscission is accentuated when trees are hedged in spring, as is commonly practiced in Australian orchards. The aim of this study was to assess the effect of the ethylene inhibitor aminoethoxyvinylglycine (AVG) on fruit abscission in macadamia and if it could be used to mitigate the effect of pruning on abscission. Racemes on ‘849’ trees that had been planted in 2002 were sprayed either pre or post anthesis with AVG at concentrations of 0, 30, 60 or 90ppm in 2007, and 0, 200, 400 or 600ppm in 2008. Whole trees that had been tip pruned at anthesis to simulate hedging, were sprayed twice (pre and post anthesis) with AVG at concentrations of 60ppm in 2007 (10-year-old ‘A4’ trees) and 400ppm in 2008 (6-year-old ‘849’ trees). Post anthesis applications to racemes increased set only slightly and the effects of low concentrations in 2007 were similar to those of high concentrations in 2008. Pre anthesis application had a similar effect to post anthesis application in 2007 but decreased initial fruit set relative to post anthesis application and the control in 2008. The increase in fruit abscission associated with pruning was not prevented by AVG application; and whole tree sprays did not increase yield on either pruned or unpruned trees. Overall the response of fruit set in macadamia to AVG in this study was poor even at high rates and with two applications. This may indicate an alternative to ethylene as the primary regulator of abscission of young macadamia fruit.

Pratylenchus brachyurus (Nematoda: Pratylenchidae) on macadamia in Brazil

Pratylenchus brachyurus was identified morphologically from root samples collected from a macadamia field in the municipality of Charqueada, located in south–eastern São Paulo, Brazil. Low numbers of the nematode were recovered from samples collected from asymptomatic macadamia trees. To our knowledge, this is the first record of P. brachyurus on macadamia in Brazil and worldwide.

ESTABILIDADE OXIDATIVA DE AMÊNDOAS DE NOZ MACADÂMIA SECAS POR MICRO-ONDAS COM AR QUENTE

The macadamia tree (Macadamia integrifolia Maiden &amp; Betche) produces a nut of highly commercial value, distinguishable from other nuts by its delicate flavour and oil quality. This study aimed to compare the oxidative stability of dried nuts, with the application of hot air microwave energy, in relation to conventional drying. The analyses were performed at the beginning stage (time zero), at 90 days, and 180 days of storage, to evaluate the percentage of free fatty acids, peroxide values, induction period, fatty acid composition, and tocopherol/tocotrienol content. The percentage of free fatty acids varied from 0.095 (MW1) to 0.124 (MW3) and from 0.123 to 0.148 (CVL); peroxide values (meq O2 kg-1 oil) ranged from 0.77 (MW2) to 2.57 (MW1) and from 1.52 to 3.29 (CVL); the induction period (h) from 16.7 (MW2) to 13.6 (MW4) and from 11.9 to 10.6 (CVL); and the ?-tocotrienol (mg 100 g-1) content from 1.75 to 2.19 (MW1) and from 2.14 to 2.19 (CVL), for microwave and conventional drying, respectively. The fatty acid composition values did not change during storage, in relation to the drying processes applied. The microwaves drying method was more efficient, regarding the macadamia nuts oxidative stability, when compared to the conventional drying method.

Shade coffee in Hawai‘i – Exploring some aspects of quality, growth, yield, and nutrition

In a harsh (Kunia) and an ideal (Kona) growing region of Hawai‘i, sun grown Coffea arabica L. was compared to coffee shaded with varying degrees of black and aluminized shade cloth, macadamia trees, and a novel, spray-on shade composed mostly of kaolin. Shading did not appreciably affect organoleptic quality. Shading resulted in statistically different yields in the macadamia (16% of sun) and kaolin (199% of sun) treatments in the second year compared to full sun treatments in their respective locations, although a negative, linear trend was observed with increased shading. The lack of significant differences in yields between the shade cloth and sun treatments was likely a result of large yield variation among replicates. Bean sizes differed little between shade treatments and the percentage of defects and broken beans were generally not significantly different among the treatments in Kunia. Kona bean sizes and characteristics were not different. Shading reduced surface leaf temperatures and increased specific leaf area but generally did not affect lateral nodal growth. Leaf nutrient concentration differed between treatments.

The production of flowers, fruit and leafy shoots in pruned macadamia trees.

For Macadamia integrifolia Maiden and Betche var. 849, we compared four limb removal strategies of varying style and severity over 4 years, in terms of effects on yield, on the distribution of light, and new vegetative shoots, racemes and fruit within the canopy. Limb removal reduced yields. The reduction corresponded with the severity of pruning, not with the style of pruning. Limb removal had little impact in the medium term on light penetration to the orchard floor. Within the canopy, shoot production and raceme production were inversely related. Shoot production was favoured by high light conditions; raceme production occurred predominantly in areas of heavy shade, with 49% of racemes produced at canopy locations receiving less than 2% full daylight, and 94% produced at locations receiving less than 16% full daylight. Most flowering appeared to occur on wood more than 3 years old. The capacity of different parts of the canopy to support fruit set and retention increased with proximity to the more irradiated parts of the canopy, but fruit production was still high deep within the lower part of the canopy, with 50% of fruit produced at canopy locations receiving less than 2% full daylight, and 90% produced at locations receiving less than 16% full daylight.

Source of Pseudocercospora macadamiae inoculum in macadamia trees and its use for characterising husk spot susceptibility in the field

Pseudocercospora macadamiae causes husk spot of macadamia. Husk spot control would be improved by knowledge of the persistence of the pathogen in orchards between seasons, and by characterising macadamia cultivars for susceptibility to infection, premature fruit abscission, and spatial escape from inoculum sources. Field observation of seven macadamia cultivars found a significant exponential relationship between husk spot incidence and the prevalence of fruit pericarp that failed to abscise (sticktights) in the canopy. Viable conidia of P. macadamiae were readily (>100 conidia per fruit) produced on sticktights for 30 months. The incidence of husk spot was up to four times greater in trees with sticktights than trees without sticktights. Assessment of the propensity to form sticktights, husk spot incidence and fruit abscission after the insertion/removal of sticktights, demonstrated differences in macadamia cultivars; cv. A16 was susceptible to infection and formation of sticktights, but tolerant of premature abscission; cv. 246 was susceptible to infection, tolerant of premature abscission, and spatially escapes P. macadamiae inoculum due to a lack of sticktights; cv. A38 was susceptible to infection, premature abscission, and sticktight formation. Our findings suggest that disease could be reduced by removing sticktights from trees, and that fungicide inputs could be reduced in trees with naturally low numbers of sticktights. In addition we show that sticktights can be used as an inoculum source for field assays to better characterise macadamia cultivars for better informed cultivar selection, and as a tool in breeding programs to screen for germplasm with high levels of resistance.