Low temperatures decrease CO2 assimilation and growth in the tropical rambutan

In glasshouse experiments, high temperatures increased vegetative growth in the tropical rambutan (Nephelium lappaceum L. seedlings of cv. Rapiah). In absolute terms, there was generally a greater response to night temperature (day/night temperatures of 32714°C vs. 32728°C) than to day temperature (22714°C vs. 32714°C), and better growth at 32728°C than at 32722°C. The effects of temperature on nutrient concentrations were small, whereas average leaf water potential (ΨL) during the day was -1.5 MPa at 32728°C, 0.1 to 0.4 MPa higher with nights of 14° or 22°C, and 0.7 MPa higher at 22714°C. Average net C02 assimilation rate (A) was 5.3 μ-mol m−2 s−1 at 32722° and 32728°C, 50% lower at 32714°C and 80% lower at 22714°C. When seedlings of cv. Rapiah were grown in water baths, the two critical root temperatures at which 90% of maximum plant weight occurred were similar for leaves and stems (about 24° to 30°C), but lower for roots (19° to 25°C). There was only a small effect of temperature on the concentration of most nutrients, and on average day time ΨL, whereas average A was 4.5 (μmol m s−1 at 28°C, 30% lower at 20°C, and 80% lower at 15° and 38°C. These experiments show that rambutan growth was strongly reduced when night or root temperatures fell to 14° or 15°C. The main effect was through lower Co−2 assimilation, whereas the changes in water and nutrient status were relatively small. Areas where night or root temperatures remain at or below 14°C for prolonged periods should be avoided for rambutan production

Bioactive phytochemicals and their bioaccessibility in four unexploited tropical fruits grown in Queensland, Australia

Tropical fruits are a popular target for health-conscious consumers worldwide. The phytochemical composition, in particular polyphenols and carotenoids, of these “exotics” is of emerging interest due to the potential health benefits of these compounds. The anthocyanin, quercetin glycoside and carotenoid composition in hog plum (Spondia dulcis), peanut butter fruit (Bunchosia armeniaca), chupa-chupa (Martisia cordata) and kwai muk (Artocarpus hypargyreus) grown in North Queensland was determined in the present study. Additionally, the release/ bioaccessibility of the determined phytochemicals as an initial measure to predict their availability for intestinal absorption was assessed using an in-vitro digestion model. Six anthocyanins could be identified in Kwai muk with cyanidin-3-glucoside as the predominant pigment (80% of total amount). Quercetin glycosides ranged between 5.6 and 8.4 mg 100 g-1 fresh weight (fw). Lycopene was identified as the main carotenoid in peanut butter fruit (21.3 mg 100 g-1 fw), whereas β-carotene was predominant in chupa-chupa (5.84 mg 100 g-1 fw), kwai muk (1.66 mg 100 g-1 fw) and hog plum (0.21 mg 100 g-1 fw). The lycopene content in peanut butter fruit was considerable and even higher than that reported for tomatoes, a popular dietary source of lycopene. Total anthocyanins (10.5 mg 100 g-1 fw) and quercetin glycosides were in the same range as reported for other fruits such as gooseberries, red currants and blueberries. Between 1-3% of carotenoids, 7-25% of quercetin glycosides and 37% of anthocyanins were released/bioaccessible after the in vitro digestion procedure. The observed low release of carotenoids from unprocessed fruits is in the same range as reported for unprocessed carrots. However, processing (e.g., blending, thermal treatment) and the addition of lipids can significantly increase the release/bioaccessibility of these lipophilic compounds. The present study clearly identified peanut butter fruit as a promising candidate for follow-up studies, in vitro and in vivo, evaluating its potential as a novel dietary source of lycopene

Inoculum source of Phytophthora palmivora, jackfruit seedlings health in response to potting media porosity, sanitation, inoculation and phosphonate application

Seedling dieback caused by Phytophthora palmivora (Butler) is a significant problem in jackfruit (Artocarpus heterophyllus Lam.) nurseries in Eastern Visayas, Philippines. It has been linked to insufficient knowledge of inoculum sources and possible factors contributing to seedlings’ health. This study was conducted to identify potential sources of Phytophthora inoculum in representative nurseries in Eastern Visayas and evaluate the effect of possible factors that contribute to seedling health. Phytophthora detection was conducted from random samples of potting media, irrigation water, germination beds, and roots of seedlings from representative nurseries supplying seedlings in the region. Detection was done through tissue baiting and the use of a Phytophthora-specific diagnostic kit. The effect of the air-filled porosity (AFP) of potting media, sanitation, pathogen inoculation, and phosphonate on plant growth and seedlings’ health was evaluated. Phytophthora propagules were positively detected in most samples, suggesting that seedlings most likely already harbor the pathogen when distributed to farms in the region. Among the factors, AFP of the potting medium had the most profound effect on seedlings’ growth and health. The tallest plants with the largest stem diameter, highest dry weight biomass, and least disease rating were grown in the most porous medium (21 % AFP) consisting of 20 % garden soil, 20 % carbonized rice hull, 20 % rice hull, 20 % coco coir dust, 10 % sand, and 10 % chicken dung. The benefit of a highly porous medium was, however, seen only when external fertilization was undertaken. Unsterilized media resulted in healthier seedlings compared to sterilized media. Sterilized potting media that were inoculated with the pathogen after sterilization resulted in more severe disease. Sterilized potting media was beneficial for jackfruit seedlings when supplied with adequate nutrients and as long as contamination with the pathogen does not occur. Sterile media, therefore, should be kept away from recontamination with the pathogen otherwise more severe disease may occur. The addition of the plant defense regulator phosphonate showed no effect on the growth and health of seedlings under the trial’s conditions. © 2021 Society for Advancement of Horticulture. All rights reserved

Inoculum source of Phytophthora palmivora, jackfruit seedlings health in response to potting media porosity, sanitation, inoculation and phosphonate application

Seedling dieback caused by Phytophthora palmivora (Butler) is a significant problem in jackfruit (Artocarpus heterophyllus Lam.) nurseries in Eastern Visayas, Philippines. It has been linked to insufficient knowledge of inoculum sources and possible factors contributing to seedlings’ health. This study was conducted to identify potential sources of Phytophthora inoculum in representative nurseries in Eastern Visayas and evaluate the effect of possible factors that contribute to seedling health. Phytophthora detection was conducted from random samples of potting media, irrigation water, germination beds, and roots of seedlings from representative nurseries supplying seedlings in the region. Detection was done through tissue baiting and the use of a Phytophthora-specific diagnostic kit. The effect of the air-filled porosity (AFP) of potting media, sanitation, pathogen inoculation, and phosphonate on plant growth and seedlings’ health was evaluated. Phytophthora propagules were positively detected in most samples, suggesting that seedlings most likely already harbor the pathogen when distributed to farms in the region. Among the factors, AFP of the potting medium had the most profound effect on seedlings’ growth and health. The tallest plants with the largest stem diameter, highest dry weight biomass, and least disease rating were grown in the most porous medium (21 % AFP) consisting of 20 % garden soil, 20 % carbonized rice hull, 20 % rice hull, 20 % coco coir dust, 10 % sand, and 10 % chicken dung. The benefit of a highly porous medium was, however, seen only when external fertilization was undertaken. Unsterilized media resulted in healthier seedlings compared to sterilized media. Sterilized potting media that were inoculated with the pathogen after sterilization resulted in more severe disease. Sterilized potting media was beneficial for jackfruit seedlings when supplied with adequate nutrients and as long as contamination with the pathogen does not occur. Sterile media, therefore, should be kept away from recontamination with the pathogen otherwise more severe disease may occur. The addition of the plant defense regulator phosphonate showed no effect on the growth and health of seedlings under the trial’s conditions. © 2021 Society for Advancement of Horticulture. All rights reserved

Tropical tree fruit research and development in the Philippines and northern Australia to increase productivity, resilience and profitability

The Philippines contains an extensive collection of tropical fruits, both indigenous and introduced (Coronel 2011) that contribute towards the livelihood of small holder farmers and village food security. The Philippine Government considers that jackfruit, durian and pomelo are emerging industries relative to their established export industry counterparts, such as banana and mango (PCAARRD, 2012) and thus they are being targeted for further research and development to assist their development and export potential. Recent statistics report that the approximate production areas occupied by jackfruit, pomelo and durian are 14,400, 5,300 and 18,800 ha with associated production volumes of 48,400, 33,400 and 77,500 metric tonnes respectively. The minor crops production data are small in comparison to major export tropical fruits such as banana (450,000 ha producing 9,100,000 tonnes) and mango (190,000 ha producing 825,000 tonnes) (Anit, 2012). Development of jackfruit, durian and pomelo beyond the current domestic supply is limited by low yields associated with disease, poor crop and postharvest management and the lack of processed product to build reliable production and export supply chains. The Australian tropical fruit industry (lychee, rambutan, pomelo, jackfruit, durian and others), whilst small in comparison, has an excellent collection of genera, species and associated varieties. The industry has developed substantially in the last 20 years and incorporated many advanced technologies. Significant inroads into production, postharvest and supply chain management have been made. In this project, jackfruit primarily was used as the model crop for investigations on the benefits of nursery hygiene, production technology and processing for industry development. The primary objectives of the project were multifaceted and included investigation into integrated disease management solutions, investigation of crop management options to improve yield and fruit quality and improved processing options

An overview of preharvest factors influencing mango fruit growth, quality and postharvest behaviour

International audienceMango, a tropical fruit of great economic importance, is generally harvested green and then commercialised after a period of storage. Unfortunately, the final quality of mango batches is highly heterogeneous, in fruit size as well as in gustatory quality and postharvest behaviour. A large amount of knowledge has been gathered on the effects of the maturity stage at harvest and postharvest conditions on the final quality of mango. Considerably less attention has been paid to the influence of environmental factors on mango growth, quality traits, and postharvest behaviour. In this paper, we provide a review of studies on mango showing how environmental factors influence the accumulation of water, structural and non-structural dry matter in the fruit during its development. These changes are discussed with respect to the evolution of quality attributes on the tree and after harvest. The preharvest factors presented here are light, temperature, carbon and water availabilities, which can be controlled by various cultural practices such as tree pruning, fruit thinning and irrigation management. We also discuss recent advances in modelling mango function on the tree according to environmental conditions that, combined with experimental studies, can improve our understanding of how these preharvest conditions affect mango growth and quality. (Résumé d'auteur)Manga, um fruto tropical de grande importância, é geralmente colhido verde e comercializado após um período de armazenamento. Infelizmente, a qualidade final da manga na prateleira é altamente heterogênea, em termos de tamanho do fruto, qualidade do paladar e comportamento pós-colheita. Tem-se obtido uma quantidade expressiva de informações sobre os efeitos do estádio de maturação e condições pós-colheita sobre a qualidade final da manga. Contudo, tem-se dado atenção consideravelmente menor à influência dos fatores ambientes sobre o crescimento da manga, características de qualidade e comportamento pós-colheita. Neste artigo, faz-se uma revisão dos estudos sobre manga, evidenciando-se como fatores ambientes afetam o acúmulo de água e de matéria seca estrutural e não-estrutural nos frutos durante o seu desenvolvimento. Discutem-se essas alterações com relação à evolução de atributos de qualidade dos frutos ainda nas plantas e após a colheita. Os fatores de pré-colheita abordados são luz, temperatura, disponibilidades de água e de carbono, raleio de frutos e manejo da irrigação. Discutem-se também recentes avanços sobre modelagem associada à função do fruto na planta, conforme as condições ambientes que, combinados com estudos experimentais, pode melhorar a nossa compreensão sobre como as condições de pré-colheita afetam o crescimento e a qualidade da manga

An Introductory Perspective to Horticulture: Plants for People and Places

Horticulture is “the first of all the arts and sciences”. This definition indicates both the breadth and depth of the discipline and its early inception as mankind changed from being hunter-gatherers to cultivators. Intensive crop production which is a form of horticulture preceded more extensive agricultural practices. From that time onwards the intricate involvement of horticulture in man’s life has become very apparent by its multitude of applications and the interests of those involved. These extend from the provision of foodstuffs and nutritional benefits through pharmaceuticals to aspects of rest and relaxation onto encouraging physical and mental well-being. Horticulture is therefore, a discipline with many components and as such that it can mean different things in the varying context of its use. This chapter introduces the meanings of horticulture as expressed by the authors who have contributed to this Trilogy of Books. They have analysed in considerable depth “Horticulture” as expressed in its facets of production, environment and society. Horticulture has impact and expression in each of these fields of human activity. This chapter also sets Horticulture into the wider context of the world of plants and their intensive cultivation both in their use by mankind and in the natural world. The aim is to demonstrate the depth and breadth of human activity associated with this discipline for it stretches from crop production, through landscape design and maintenance and into aspects of society and its expression in the arts and humanities. Horticulture touches almost every aspect of human activity. Increasingly Horticulture has significant importance in contributing towards the mitigation of the major problems which now face life on Earth such as:- climate change, food security, the loss of natural biodiversity, pollution, resource erosion and over-population. Indeed despite or perhaps because of its antiquity and therefore its strong connection between science, technology and practice horticulture can offer solutions that might allude other disciplines