Selecting for Nut Characteristics in Macadamia Using a Genome-wide Association Study

O’Connor, Katie; Hayes, Ben J.; Hardner, Craig; Alam, Mobashwer; Topp, Bruce

doi:10.21273/hortsci13297-18

Cited by 16 publications

(32 citation statements)

References 14 publications

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“…These relationships between nut and kernel parameters are consistent with previous results within cultivars "A4", "246" and "660" [45,46]. Strong positive correlations have also been found between nut mass and kernel mass across macadamia cultivars, although non-significant or negative correlations have been detected between nut mass and kernel recovery [49,50]. The average kernel recovery from Australian macadamia orchards is approximately 34% and growers receive a premium for producing nuts with higher kernel recovery [51,52].…”

Section: Kernel Recovery and Incidence Of Whole Kernelssupporting

confidence: 90%

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

Richards

Kämper

Trueman

et al. 2020

Plants

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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.Plants 2020, 9, 228 2 of 14 also a valuable source of calcium, iron and zinc, which can be absorbed insufficiently during phases of high dietary demand such as infancy, childhood, adolescence, pregnancy and breastfeeding [16][17][18][19][20][21].The fatty acid composition and nutrient concentrations of tree-nut kernels can vary greatly among cultivars [9,[22][23][24][25][26][27][28]. Fatty acid composition and nutrient concentrations can also vary within almond or pistachio cultivars because of differences in the pollen parentage of individual kernels [22][23][24][25]29,30]. For example, self-pollinated kernels of some almond cultivars have lower oleic:linoleic acid ratios than cross-pollinated kernels [25,29]. In addition, self-pollinated kernels of some almond, chestnut and hazelnut cultivars are smaller than cross-pollinated kernels [22,[31][32][33]. Such effects of the paternal genetic background on the size or quality of the embryo are termed "xenia", and xenic effects are common in fruit and nut crops [34]. Therefore, maximising both yield and human-health benefits may depend upon ensuring high levels of cross-pollination in tree-nut orchards.Relationships between kernel size, nutritional composition, and cross-or self-paternity are poorly understood for some nuts, including the subtropical tree nut, macadamia (Macadamia integrifolia, M. tetraphylla and hybrids). Macadamia flowers are bee-pollinated and partially self-incompatible [35][36][37][38][39][40][41][42]...

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Section: Kernel Recovery and Incidence Of Whole Kernelssupporting

confidence: 90%

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

Richards

Kämper

Trueman

et al. 2020

Plants

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“…Large phenotypic diversity was observed for many of the traits in this study. Average phenotypic values observed here for NW, KW and KR (7.09 g, 2.73 g, and 38.7%, respectively) were all slightly higher compared with the same traits when the trees were young (6.21 g, 2.28 g, and 36.9%) (32).…”

Section: Phenotypic Data In the Breeding Programcontrasting

confidence: 42%

“…It is hypothesised that marker-trait associations will be detected for these key traits using GWAS, and upon validation could be combined with MAS to improve breeding efforts and increase genetic gain in macadamia. The current study builds on work previously published in a preliminary study (32) on the same population of trees. O'Connor, Hayes (32) found SNP markers associated with three nut characteristics (NW, KW and KR) measured on trees at the ages of 7-9 years (in 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The current study builds on work previously published in a preliminary study (32) on the same population of trees. O'Connor, Hayes (32) found SNP markers associated with three nut characteristics (NW, KW and KR) measured on trees at the ages of 7-9 years (in 2010). In comparison, the current study uses a different set of SNP markers imputed with high accuracy, and performs GWAS on yield component traits measured on the same trees at a mature age (aged 14-17 years, in 2016-2018).…”

Section: Introductionmentioning

confidence: 99%

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Genome-wide association studies for yield component traits in a macadamia breeding population

O’Connor

Hayes

Hardner

et al. 2019

Preprint

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Background: Breeding for new macadamia cultivars with high nut yield is expensive in terms of time, labour and cost. Most trees set nuts after four to five years, and candidate varieties for breeding are evaluated for at least eight years for various traits. Genome-wide association studies (GWAS) are promising methods to reduce evaluation and selection cycles by identifying genetic markers linked with key traits, potentially enabling early selection through marker-assisted selection. This study used 295 progeny from 32 full-sib families and 29 parents (18 phenotyped) which were planted across four sites, with each tree genotyped for 4,113 SNPs. ASReml-R was used to perform association analyses with linear mixed models including a genomic relationship matrix to account for population structure. Traits investigated were: nut weight (NW), kernel weight (KW), kernel recovery (KR), percentage of whole kernels (WK), tree trunk circumference (TC), percentage of racemes that survived from flowering through to nut set, and number of nuts per raceme. Results: Seven SNPs were significantly associated with NW (at a genome-wide false discovery rate of <0.05), and four with WK. Multiple regression, as well as mapping of markers to genome assembly scaffolds suggested that some SNPs were detecting the same QTL. There were 44 significant SNPs identified for TC although multiple regression suggested detection of 16 separate QTLs. Conclusions: These findings have important implications for macadamia breeding, and highlight the difficulties of heterozygous populations with rapid LD decay. By coupling validated marker-trait associations detected through GWAS with MAS, genetic gain could be increased by reducing the selection time for economically important nut characteristics. Genomic selection may be a more appropriate method to predict complex traits like tree size and yield.

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“…Areas of research included propagation, tree physiology, soils and nutrition, pollination biology, pest and disease biology, orchard management, genetics and breeding, developing production areas, and product development. Seven of the presentations are published in this special section Hardner et al, 2019;Howlett et al, 2019;O'Connor et al, 2019;O'Hare et al, 2019;Toft et al, 2019;Zhao et al, 2019).…”

Section: Summary Of Presentationsmentioning

confidence: 99%

Global Macadamia Science: Overview of the Special Section

Hardner¹,

Wall²,

Cho³

2019

horts

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Macadamia is a rapidly developing global crop; however, limited cultivation history and size of the industry means many challenges remain to support sustained productivity and profitability of this industry. This paper summarizes oral and poster presentations, and subsequent papers included in this volume, delivered at the 2017 International Macadamia Research Symposium, held in Hilo, HI, in September of that year. This was the first international meeting of macadamia researchers since 1992. The 28 oral and seven poster presentations covered propagation technology, tree physiology, soils and nutrition, pollination, pest and disease, orchard management, genetics and breeding, product development, and new production regions. Notable messages were that micrografting of macadamias is commercially viable; planting density and girdling could increase early yield per hectare; resource availability may limit cross-pollination yield; and yield production of individual branches is not independent. Integrated pest HORTSCIENCE VOL. 54(4) APRIL 2019

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Selecting for Nut Characteristics in Macadamia Using a Genome-wide Association Study

Cited by 16 publications

References 14 publications

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

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

Genome-wide association studies for yield component traits in a macadamia breeding population

Global Macadamia Science: Overview of the Special Section

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