Mango Breeding Support

The Mango Breeding Support project provided technical, research and development support to the Queensland-based, Australian Mango Breeding Program to develop and evaluate breeding systems and technologies that improve mango breeding efficiency. Adoption of efficient breeding support technologies will allow breeders to identify genes for desirable plant and fruit traits in parent varieties and incorporate those genes into new hybrid varieties more efficiently and rapidly. The project compared traditional hand pollination methods with DNA marker assisted selection (MAS) open-pollinated methods to identify paternity and found both systems had advantages. Marker assisted paternity identification was not practical in all cases and relied on a greater range of technical skills and resources being available to the breeder. It is expected that MAS will become even more efficient when markers are available for production and quality traits in addition to parental identification. Breeding for anthracnose resistance in mango is in its infancy. This project has identified several accessions in related Mangifera species with potential tolerance to postharvest anthracnose and tested the compatibility of these related species with the common mango and if the tolerance is transferable. The project investigated ways of determining a trees postharvest fruit disease resistance status in seedlings to avoid the up to 6 year wait for trees to crop. Identification of genes and gene markers for plant development, stress response, fruit colour and flavour development was another goal of this project. Twenty five new expressed sequence tag (EST) derived single sequence repeat (SSR) DNA markers were identified and tested across a diverse range of germplasm. These markers were shown to be useful in determining genetic relationships, exploring potential pedigrees and estimating the genetic background of cultivated accessions of M. indica. They are the first reported EST-SSR markers suitable to cross-amplify in five wild Mangifera species. The technologies that have been shown to be more efficient have been incorporated in to the Australian Mango Breeding Project. Other technologies being researched that are not yet fully developed to the stage where they can be adopted in a working breeding program are being progressed in other related research projects

Mango Breeding Support

The Mango Breeding Support project provided technical, research and development support to the Queensland-based, Australian Mango Breeding Program to develop and evaluate breeding systems and technologies that improve mango breeding efficiency. Adoption of efficient breeding support technologies will allow breeders to identify genes for desirable plant and fruit traits in parent varieties and incorporate those genes into new hybrid varieties more efficiently and rapidly. The project compared traditional hand pollination methods with DNA marker assisted selection (MAS) open-pollinated methods to identify paternity and found both systems had advantages. Marker assisted paternity identification was not practical in all cases and relied on a greater range of technical skills and resources being available to the breeder. It is expected that MAS will become even more efficient when markers are available for production and quality traits in addition to parental identification. Breeding for anthracnose resistance in mango is in its infancy. This project has identified several accessions in related Mangifera species with potential tolerance to postharvest anthracnose and tested the compatibility of these related species with the common mango and if the tolerance is transferable. The project investigated ways of determining a trees postharvest fruit disease resistance status in seedlings to avoid the up to 6 year wait for trees to crop. Identification of genes and gene markers for plant development, stress response, fruit colour and flavour development was another goal of this project. Twenty five new expressed sequence tag (EST) derived single sequence repeat (SSR) DNA markers were identified and tested across a diverse range of germplasm. These markers were shown to be useful in determining genetic relationships, exploring potential pedigrees and estimating the genetic background of cultivated accessions of M. indica. They are the first reported EST-SSR markers suitable to cross-amplify in five wild Mangifera species. The technologies that have been shown to be more efficient have been incorporated in to the Australian Mango Breeding Project. Other technologies being researched that are not yet fully developed to the stage where they can be adopted in a working breeding program are being progressed in other related research projects

Mango germplasm screening for the identification of sources of tolerance to anthracnose

Colletotrichum species are one of the most common causes of postharvest fruit rot in mango in Australia, particularly in the tropical region of north Queensland, and can result in significant losses if not managed. The research aims were to identify sources of anthracnose tolerance and to determine if host material other than fruit could improve or fast track the screening process and result in improved breeding efficiency. Access to the Australian National Mango Genebank (ANMG) collection enabled fruit screening of more than 100 Mangifera indica cultivars or Mangifera species for tolerance to anthracnose by artificial inoculation with Colletotrichum asianum over a period of 14 years. Mean lesion diameters were compared with those on a known susceptible M. indica cultivar Kensington Pride (KP) and a tolerant M. laurina cultivar Lombok. Inoculation of leaf discs and entire leaves was evaluated in the laboratory and the field as alternative assays for tolerance to anthracnose and was assessed by presence/absence of disease. Screening of fruit has shown that anthracnose tolerance within the mango germplasm is highly variable and needs to be assessed over multiple years. None of the alternative laboratory bioassays provided consistent or reliable data. The in-field artificial inoculation of immature leaf flush was successful but was not deemed suitable for adoption due to practical restraints. While resistance to anthracnose in fruit has not yet been identified, some cultivars and Mangifera spp. showed promise for inclusion as parents in future breeding programs

Do soil applications of fulvic acid applied with potassium sulphate influence mango fruit quality?

The effects of fulvic acid as a supplement to potassium (K) applications on mango fruit quality, flower synchronisation and yield were investigated in an 8-year-old 'Kensington Pride' (KP) orchard over two seasons, at Southedge Research Station in Far North Queensland, Australia. The aim of the trial was to determine whether fulvic acid (FA) improved the efficiency of potassium uptake. Experimental treatments included i) nil K + nil FA, ii) 800 g K tree-1, and iii) 800 g K + 300 mL FA tree-1. Treatments were applied approximately every 3 weeks, after fruit set and during the fruit filling stage through to harvest. Treatment effects were assessed by measuring tree yield, fruit weight, length, depth and width, the incidence of post-harvest disease, ground skin colour at eating-ripe stage, as well as the proportion of canopy flowering in different stages in the following season. Results indicated that neither K fertiliser nor FA increased average fruit number or yield. In the first year, K combined with FA significantly increased the proportion of fruit with no lenticel spotting and the lightness of the ground skin colour of eating-ripe mangoes. By the second season, K with or without FA significantly increased the average fruit length and foliar dry-matter K concentration, while fruit weight was only marginally increased when compared to the nil K treatment. In summary, the addition of K applied during fruit development led to improved fruit size and maintenance of foliar K concentrations 2 years after application. However, although the addition of FA with K fertiliser reduced the proportion of fruit with lenticel spotting, this result was only observed in the first season of the trial and hence would require further research to confirm

How do preharvest applications of nitrogen fertiliser affect branch growth, leaf morphology and fruit, in Mangifera indica (mango) orchards?

The effect of preharvest applications of nitrogen (N) fertiliser to mango trees during the late fruit maturation stage was investigated over 3 years (2012-2014) to determine the effects on canopy growth in 8 year-old 'Kensington Pride' (KP) mango trees grown in Queensland. The experiment consisted of six treatments where 156 g N tree-1 was applied as a single treatment, as 340 g of urea or split between three different times. The N treatments were 1) 100% of N 2 weeks postharvest (control), 2) 50% of N 2 weeks preharvest, plus 50% 2 weeks postharvest, 3) 65% 2 weeks preharvest, plus 35% 2 weeks postharvest, 4) 35% 4 weeks preharvest plus 65% 2 weeks postharvest, and 5) 65% 4 weeks preharvest, plus 35% 2 weeks postharvest. Vegetative growth was investigated at the branch, sub-branch (shoots), growth unit (GU) and leaf scales. Branches from different aspects (north, south, east and west), in the upper and lower canopy were assessed, and for 2 branch types (apical or lateral) was considered. Fruit counts were also considered at the branch level. Results showed that when 50-65% of the N was applied 2 and 4 weeks before harvest with the balance 2 weeks postharvest, the number of branches, branch length and fruit count increased. When 35% N was applied 4 weeks preharvest with the balance 2 weeks postharvest, only stem biomass was increased. Generally, branches in the upper canopy had longer sub-branches, longer and thicker, first level growth units, shorter leaf petioles and shorter and thinner leaves compared to those in the lower canopy. The SPAD N index was lowest in the northern canopy aspect. Differences were also observed between lateral and apical branches. Lateral branches had longer leaves than apical branches while apical branches had a trend for higher leaf area, stem biomass and leaf counts. There were also negative relationships between fruit count and measurements for stem biomass, leaf count and leaf area for apical branches however for lateral branches these relationships were positive. In summary, when a higher proportion of N was applied 2 or 4 weeks prior to harvest the partitioning of growth to leaves and stem increased while low rates of N applied prior to harvest led to increased stem biomass only. Applications of N 2 or 4 weeks prior to harvest resulted in increased fruit count and more efficient nitrogen use efficiency (NUE), although the relationship between fruit count, and leaf and stem growth was dependent on branch type. © 2020 International Society for Horticultural Science. All rights reserved

The effect of rootstocks on mango tree vigour, scion architecture, yield, percentage of flowering terminals in young unpruned trees

In Australia, commercial tree size management in mango orchards involves annual machine hedging and heavy hand pruning. In tropical growing regions, heavy pruning often stimulates strong vegetative regrowth that is less likely to flower due to insufficient terminal growth-unit dormancy required for flowering. A few mango rootstocks have been shown to reduce scion vigour and maintain regular, high yields; however, there is a lack of rigorous field-testing of these and other rootstocks under Australian scions growing in Queensland. Apart from some scion vigour control, the effects of mango rootstocks on scion architecture have not been studied in Australia and reports in the international literature are scarce. In this study, 90 genetically diverse rootstocks have been evaluated for their ability to reduce vigour in two Australian mango scion varieties from the National Mango Breeding Program (NMBP); ‘NMBP-1243’ and ‘NMBP-4069’. Tree height, canopy volume and shape, rootstock and scion trunk cross-sectional area were measured in young trees 30 months after planting to evaluate tree growth and vigour. Branch angle, length and diameter, number of growth units, number of leaves, and leaf size were also measured to characterize scion architecture. Ten rootstocks were identified as reducing vigour while maintaining the percentage of flowering terminals per canopy volume. Four rootstocks were also found to influence scion architecture by altering secondary branch angles to be closer to horizontal, potentially making them more suited to single-leader training used in high-density orchards systems. Canopy architecture parameters measured in this study suggest that rootstocks may be a useful technique for reducing tree vigour and altering the architecture of mango scion canopies to make them more suited to intensive orchard systems. © 2022 International Society for Horticultural Science. All rights reserved

Identifying vigour controlling rootstocks for mango

Vigour reduction in many tree crops is an essential element of highly productive, high density systems that is often achieved through rootstocks. Mangoes are large vigorous tropical trees that are traditionally grown at low density as suitable vigour reducing technologies are not commercially available. The aim of this work was to identify rootstock cultivars for mango that reduced scion vigour while maintaining or boosting yields. Ninety rootstocks are being evaluated for their ability to reduce vigour in two Australian mango scion cultivars from the National Mango Breeding Program (NMBP); ‘NMBP-1243’ and ‘NMBP-4069’. The evaluated rootstocks were sourced from a wide genetic range within Mangifera indica and related Mangifera spp. from the Australian National Mango Gene Bank and the Australian Mango Breeding Program. Rootstock-scion combinations were field planted at Walkamin, Queensland, Australia over three years, from May 2014 in randomised incomplete blocks. Tree height, canopy depth, canopy length (along the row), canopy width (across the row), rootstock trunk diameter (10 cm above the ground and 10 cm below the graft point) and scion diameter (10 cm above the graft) were measured every six months as indicators of tree growth and vigour. This is a report on the progress of 29 rootstocks from the May 2014 planting. There was a significant (p<0.05) effect of rootstock on tree height, canopy size and trunk diameter at 24 months. Seven rootstocks were consistently among the 13 lowest vigour trees for tree height, canopy length, canopy width and scion/rootstock trunk diameters, when ranked from lowest to highest vigour. These rootstocks show promise for high-density mango orchard systems. Evaluation is ongoing and will evaluate effect of rootstock on scion flowering and cropping

Setting a National Agenda for Surgical Disparities Research: Recommendations From the National Institutes of Health and American College of Surgeons Summit

Health care disparities (differential access, care, and outcomes owing to factors such as race/ethnicity) are widely established. Compared with other groups, African American individuals have an increased mortality risk across multiple surgical procedures. Gender, sexual orientation, age, and geographic disparities are also well documented. Further research is needed to mitigate these inequities. To do so, the American College of Surgeons and the National Institutes of Health-National Institute of Minority Health and Disparities convened a research summit to develop a national surgical disparities research agenda and funding priorities. Sixty leading researchers and clinicians gathered in May 2015 for a 2-day summit. First, literature on surgical disparities was presented within 5 themes: (1) clinician, (2) patient, (3) systemic/access, (4) clinical quality, and (5) postoperative care and rehabilitation-related factors. These themes were identified via an exhaustive preconference literature review and guided the summit and its interactive consensus-building exercises. After individual thematic presentations, attendees contributed research priorities for each theme. Suggestions were collated, refined, and prioritized during the latter half of the summit. Breakout sessions yielded 3 to 5 top research priorities by theme. Overall priorities, regardless of theme, included improving patient-clinician communication, fostering engagement and community outreach by using technology, improving care at facilities with a higher proportion of minority patients, evaluating the longer-term effect of acute intervention and rehabilitation support, and improving patient centeredness by identifying expectations for recovery. The National Institutes of Health and American College of Surgeons Summit on Surgical Disparities Research succeeded in identifying a comprehensive research agenda. Future research and funding priorities should prioritize patients' care perspectives, workforce diversification and training, and systematic evaluation of health technologies to reduce surgical disparities