Psidium

Psidium is a genus of approximately 78 accepted species of shrubs and trees in the family Myrtaceae, native to the Neotropics from 30°N in Mexico to 38°S in Argentina, including the West Indies, Galápagos, and Revillagigedo Islands.^[1][2] The plants are characterized by evergreen habits, opposite or subopposite leaves that are often gland-dotted, white flowers typically pollinated by bees, and fleshy berries dispersed primarily by mammals.^[1] The genus exhibits high levels of polyploidy and has undergone rapid diversification since approximately 25 million years ago, forming four major phylogenetic sections: Psidium, Obversifolia, Apertiflora (31 species), and Mitranthes (26 species).^[1] The most notable species is Psidium guajava, the common guava, a small tree or shrub growing up to 10 meters tall with smooth, flaking bark and producing round to pear-shaped fruits rich in vitamins C and A.^[3] Native to tropical America, P. guajava has been widely cultivated and naturalized in tropical and subtropical regions worldwide for its edible fruit, which is consumed fresh, in juices, and processed products, contributing significantly to global agriculture and trade.^[4] Other species, such as Psidium cattleyanum (strawberry guava), are economically important but also highly invasive in non-native ecosystems like Hawaii and Florida, where they outcompete native vegetation and alter habitats.^[1] Psidium species have been studied for their phytochemical diversity, including flavonoids, terpenoids, and essential oils, which contribute to traditional medicinal uses for treating diarrhea, inflammation, and respiratory issues, though further clinical validation is needed.^[5] The genus's biodiversity hotspots are in the West Indies (especially Cuba and Hispaniola), central and southern Brazil, Paraguay, and northern South America, underscoring its ecological significance in Neotropical forests.^[1]

Taxonomy and Etymology

Etymology

The genus name Psidium was coined by Carl Linnaeus in his seminal 1753 publication Species Plantarum, where he first described the taxon encompassing guava and related species.^[6][7] Linnaeus derived Psidium from the Latin psidium, itself borrowed from the Ancient Greek ψίδιον (psídion), a classical term denoting the pomegranate (Punica granatum). This naming reflects the perceived resemblance between the fruits of Psidium species—characterized by a central core surrounded by numerous seeds embedded in fleshy tissue—and those of the pomegranate.^[8][9] Classical sources occasionally interpret psídion more broadly as "a kind of fruit" or even "a pouch or bag," potentially alluding to the enclosed, berry-like structure of the guava fruit rather than a direct pomegranate analogy. However, Linnaeus's intent centered on the visual and structural similarity to Punica, establishing the etymological foundation for the genus in botanical nomenclature.^[9][10]

Taxonomic Classification

The genus Psidium is placed within the kingdom Plantae, phylum Tracheophyta, class Magnoliopsida, order Myrtales, family Myrtaceae, subfamily Myrtoideae, tribe Myrteae, and genus Psidium.^[11] This hierarchical classification aligns with the Angiosperm Phylogeny Group IV (APG IV) system, which integrates molecular and morphological data to define angiosperm orders and families, including Myrtales and Myrtaceae.^[12] The type species of the genus is Psidium guajava L., designated based on its morphological distinctiveness and historical precedence within Linnaean descriptions.^[13] As per Plants of the World Online (accessed November 2025), approximately 78 species are accepted in the genus, though phylogenetic studies recognize up to 92 species, reflecting ongoing refinements to account for synonymy, regional variation, and recent descriptions such as Psidium urquiolanum from Cuba in 2023.^[2][1][14] The genus Psidium was established by Carl Linnaeus in his 1753 work Species Plantarum, where he described several species based on specimens from the Americas, initially placing it within the Myrtaceae family under early botanical systems.^[2] Subsequent revisions, particularly by Leslie R. Landrum in the late 20th and early 21st centuries, have clarified species boundaries through detailed morphological analyses of complexes such as P. grandifolium and P. salutare, reducing earlier estimates of up to 150 taxa by resolving synonyms and describing new entities.^[15][16] These efforts, combined with the adoption of APG IV in 2016, have solidified Psidium's position in contemporary taxonomy while accommodating neotropical diversity.^[12]

Phylogenetic Relationships

Psidium is positioned within the tribe Myrteae of the family Myrtaceae, specifically in the Main Neotropical Lineage, where it forms part of the Psidium group alongside genera such as Mosiera and Myrrhinium, and some species of Calyptrogenia.^[17] This group is sister to other major Neotropical clades, including those encompassing Eugenia and Campomanesia, with phylogenetic analyses indicating a nested relationship where Campomanesia is basal to a subclade containing Psidium (often with Acca as a close relative) and further nested with Eugenia via intermediates like Pimenta and Plinia.^[17][18] Molecular studies using chloroplast and nuclear markers have consistently resolved these relationships, highlighting the hyper-diverse nature of Myrteae within Myrtaceae, which comprises over 1,300 species across 49 genera predominantly in the Neotropics.^[17] Molecular phylogenetic evidence confirms Psidium as monophyletic, with strong support for four major clades corresponding to infrageneric sections, based on analyses of nuclear ITS and plastid regions like trnL-trnF and rpl16.^[19] This monophyly is underscored by rapid diversification in the Neotropics, evidenced by elevated net diversification rates at the Psidium group crown node, estimated around 39 million years ago (using macrofossils) or 25 million years ago (using pollen fossils), coinciding with Oligocene climatic shifts that promoted speciation in South American lineages.^[17] These patterns reflect the tribe's broader burst of diversification in the Neotropics following the Eocene-Oligocene transition.^[17] The fossil record supports ancient origins for the Psidium lineage, with Paleogene macrofossils from Patagonia assigned to the genus, including Psidium membranaceum, P. araciforme, P. licciardoi, and Psidium sp., dated to the Paleocene-Eocene (approximately 57-37 million years ago).^[20] These fossils, characterized by leaf venation and morphology akin to modern Psidium, indicate an early presence of the genus in southern South American floras, consistent with the Paleocene Paleomyrtinae princetonensis showing affinities to Psidium or related Mosiera.^[20][17] Evolutionary adaptations in Psidium are prominently linked to fruit development, where the genus uniquely evolved fleshy, indehiscent endocarps in addition to fleshy pericarp walls, distinguishing it from other fleshy-fruited Myrteae and enhancing seed dispersal by vertebrates.^[1] In species like P. guajava, selection for larger fruits with high sugar content likely drove polyploidy (prevalent in 85.7% of studied species) and biochemical innovations, such as increased terpenoid production for defense and attraction, facilitating adaptation to diverse Neotropical habitats.^[20][21][22]

Description

Habit and Morphology

Psidium species exhibit a habit as evergreen shrubs or small trees, commonly growing to heights of 3–10 m, though some forms range from recurrent sub-shrubs less than 1 m tall to larger trees exceeding 10 m.^[1][20] The bark is typically smooth and thinly exfoliating in strips or patches, often appearing coppery or reddish, particularly in mature individuals.^[1][23] Leaves in the genus are opposite and simple, displaying considerable variation in size from 0.4 cm to 19 cm long, though most are elliptic to ovate and measure 5–15 cm in length.^[1] They are generally leathery (coriaceous), with prominent venation that can be brochidodromous, acrodromous, or camptodromous, and often feature glandular dots or pellucid punctations.^[1] The leaf epidermis is uniseriate, typically hypostomatic with paracytic stomata, and may bear tector trichomes.^[1] Stems and branches are quadrangular or alate when young, becoming terete with age, and show sectional variations such as compressed forms in certain groups within the genus.^[1] Across Psidium, growth forms vary by habitat and section, with shrubby, understory-adapted species like those in section Mitranthes contrasting taller, canopy-reaching trees in section Psidium, often influenced by edaphic factors such as sandy or water-logged soils.^[1]

Flowers, Fruits, and Seeds

The flowers of Psidium species are typically white and aromatic, borne solitary or in small cymes of two to three (occasionally up to seven) in the leaf axils.^[1] They measure 2–3 cm in diameter, with a campanulate hypanthium about 5 mm long that is often pubescent.^[24] The calyx consists of five sepals fused into a rounded cap 7–12 mm long, which splits irregularly at anthesis and may persist into fruit; the corolla has five white, obovate to elliptic petals 10–22 mm long.^[25] Stamens are numerous, ranging from 80 to 720, 5–15 mm long, with small anthers (0.3–3 mm) often bearing an apical gland; the single style equals or exceeds the stamens in length, ending in a punctiform, funnel-shaped, or capitate stigma.^[1] The inferior, syncarpous ovary is 2–6-locular with 3–180 ovules per locule, featuring stone cells in the walls and schizogenous secretory cavities containing resinous essential oils, a characteristic trait of the Myrtaceae family.^[1][26][27] Fruits in the genus Psidium are fleshy berries derived from the syncarpous gynoecium, typically globose to pyriform and 1.5–6 cm in diameter, though smaller (8–45 mm) in some sections.^[1] The pericarp includes a thin, leathery exocarp that is green when immature and turns yellow, yellow-green, crimson, or red at maturity, enclosing edible, aromatic mesocarp and endocarp with juicy pulp; persistent sepals may crown the apex.^[1] For example, fruits of P. guajava reach 3–10 cm, with yellow skin and pink or cream pulp, while those of P. cattleianum are 2–4.5 cm and yellow or crimson.^[25][1] The berries develop from the inferior ovary's fleshy walls and placentas, containing 1–325 seeds embedded in the central pulp, and exhibit glandular resin throughout, contributing to their distinctive scent.^[1][28] Seeds of Psidium are reniform, 1–10 mm long (typically 2–5 mm), with a hard, bony testa 5–30 cells thick and a pulpy outer layer; an operculum facilitates water imbibition during germination.^[1] They are numerous per fruit in most species, though rarely as few as one, and range from smooth (e.g., in P. guajava) to angular when tightly packed, embedded within the translucent pulp.^[1] The seeds feature a dense cellular structure unique among Myrteae, with cream to tan coloration and no dormancy in some species like P. guineense.^[1][29]

Reproduction

Psidium species primarily engage in sexual reproduction, which is predominantly allogamous and relies on insect pollination for effective pollen transfer.^[30][31] In species such as P. guajava, self-incompatibility mechanisms reduce fruit set from self-pollination by up to 39.5%, promoting cross-pollination to ensure reproductive success.^[30] In P. guajava, breeding systems are typically open-pollinated, with outcrossing rates of 35–40% that sustain high levels of genetic diversity through heterozygosity in progeny.^[32] Asexual reproduction occurs via vegetative propagation, including methods such as stem cuttings, air layering, and root suckers, which allow clonal propagation and are commonly used in cultivation to maintain desirable traits.^[33][34] Additionally, apomixis has been documented in certain taxa, such as P. cattleyanum forms cattleyanum and lucidum, where diplospory produces unreduced embryo sacs leading to seed formation without fertilization, resulting in genetically uniform offspring.^[35] Seeds of Psidium are orthodox, exhibiting physical dormancy due to impermeable seed coats that can be overcome through scarification treatments, such as exposure to 20% sulfuric acid for 3 minutes, achieving germination rates up to 51.7%.^[36][37] Under optimal storage conditions, such as desiccation to 5–8% moisture content and low temperatures (e.g., 5°C), seed viability is maintained for up to 90 days to a year, supporting long-term conservation.^[38]

Distribution and Habitat

Native Range

The genus Psidium is native to the Neotropics, with its core distribution spanning tropical and subtropical regions from approximately 30°N in the State of Sonora, Mexico, southward through Central America, the Caribbean (including the West Indies), and into northern and eastern South America as far as 38°S in the Province of Buenos Aires, Argentina.^[1] This range encompasses countries such as Mexico, Guatemala, Honduras, Nicaragua, Costa Rica, Panama, Colombia, Venezuela, Peru, Ecuador, Brazil, Paraguay, Bolivia, and Uruguay, as well as island groups like the Galápagos and Revillagigedo Islands.^[1][20] Centers of diversity for Psidium are concentrated in Brazil, the West Indies, Paraguay, and northern South America, where the highest species richness occurs, with notable diversity also in Mexico, including numerous endemics adapted to montane forests and coastal zones. Brazil hosts approximately 50–60 species, representing a significant portion of the genus's approximately 92 accepted species, with particular hotspots in eastern and central regions.^[20][39] Mexico also features notable diversity, particularly in southern and central areas, contributing to the genus's overall endemism.^[1] Additional centers include the West Indies (e.g., 22 species in Cuba) and northern South America (e.g., Peru and Venezuela).^[1] The historical biogeography of Psidium reflects the broader Neotropical radiation of the tribe Myrteae within Myrtaceae, a family of Gondwanan origin that diversified following the breakup of Gondwana in the late Cretaceous to Paleogene.^[17] Disjunct distributions across the Neotropics, such as between the Caribbean islands and mainland South America, are linked to vicariance events, overland dispersal via ancient Antarctic connections, and subsequent long-distance dispersal during the Oligocene–Miocene, with the genus itself undergoing rapid diversification around the Oligocene–Miocene boundary.^[17][40] This evolutionary history has resulted in polyploidy and apomixis facilitating adaptation to varied environments.^[1] Within its native range, Psidium occupies specific ecoregions such as the Atlantic Forest and Cerrado biomes in Brazil, the Amazon Basin (particularly riparian zones), and the Andean slopes in countries like Peru, Colombia, and Ecuador.^[1][20] These areas support species in diverse habitats, from humid tropical forests to semi-deciduous woodlands and savannas.^[20]

Introduced Distributions

Psidium species, particularly P. guajava and P. cattleyanum, have been introduced to numerous regions outside their native Neotropical range through human activities, leading to widespread cultivation and naturalization in tropical and subtropical areas worldwide.^[4][20] Introductions began in the 16th century via Spanish and Portuguese colonial trade, with P. guajava first documented in the West Indies by 1535 and subsequently spread to Asia, Africa, and the Pacific by the 17th–19th centuries.^[4][20] In Asia, P. guajava is widely naturalized in India and Southeast Asia, where it was introduced for fruit production and has established feral populations in disturbed areas.^[4] Similarly, tropical zones of Africa, including East Africa, host naturalized stands of P. guajava, often escaping cultivation to form invasive thickets.^[4] In the Pacific Islands, such as Hawaii and parts of Polynesia, both P. guajava and P. cattleyanum have become established, with the latter introduced in the early 1800s for its edible fruit.^[4][41] P. cattleyanum also occurs in Australia, where it has naturalized in subtropical regions.^[41] Notable invasive occurrences include P. guajava and P. cattleyanum in Hawaii and Florida, where they were introduced via fruit trade and ornamental plantings in the 19th century, leading to dense stands that displace native vegetation.^[4][41] In the Mediterranean parts of Europe, such as Greece, P. guajava is cultivated but has limited naturalization due to cooler climates.^[42] Overall, Psidium species are now cultivated in more than 60 countries across tropical and subtropical zones, with feral populations common in humid, disturbed habitats.^[43]

Habitat Preferences

Psidium species are predominantly adapted to tropical and subtropical climates, where they favor mean annual temperatures of 20–30°C and well-distributed rainfall ranging from 1000 to 2000 mm, although they demonstrate notable tolerance to seasonal droughts that can extend for several months. This climatic preference supports optimal growth and fruiting, with deviations leading to reduced productivity; for instance, temperatures below 15°C may inhibit flowering in many taxa.^[44][4] In terms of soil, Psidium thrives in well-drained sandy loams or similar textures that prevent waterlogging, with an optimal pH between 4.5 and 7.0, though some species accommodate slightly more alkaline conditions up to pH 8.5 when provided with micronutrients like iron. Coastal representatives, such as Psidium cattleyanum, exhibit tolerance to saline soils, enabling establishment in brackish environments, while the genus generally copes with nutrient-poor or rocky substrates through efficient nutrient uptake mechanisms.^[45][46] These plants commonly occupy ecosystems characterized by disturbance, including forest edges, riverbanks, and secondary regrowth in savannas or semi-deciduous woodlands, spanning an altitudinal gradient from sea level to approximately 2000 m. Such habitats provide the light exposure and moisture variability that align with the genus's ecological niche, often facilitating rapid colonization post-disturbance.^[1][47] Key adaptations include drought resistance achieved through physiological adjustments like reduced transpiration and efficient water use, alongside deep taproot systems in mature individuals that access subsurface moisture. Certain understory species, exemplified by Psidium cattleyanum, display shade tolerance, allowing persistence in partially canopied areas with lower light intensities.^[4][44][48]

Ecology

Pollination and Dispersal

Pollination in Psidium species is predominantly entomophilous, relying on insects such as bees (Apis mellifera), flies, beetles, and butterflies as primary vectors.^[49] Honey bees, in particular, are the chief pollinators, transferring pollen between flowers where pollen serves as the main reward rather than nectar.^[50] Cross-pollination predominates in wild populations, promoting genetic diversity, though cultivated varieties like P. guajava can achieve partial self-pollination, reducing dependence on external agents.^[51] Seed dispersal in Psidium occurs mainly via zoochory, with frugivorous birds and mammals consuming the fruits and depositing viable seeds through feces away from the parent plant.^[4] In native Neotropical habitats, birds such as toucans (Ramphastidae) and mammals including monkeys and bats effectively spread seeds over distances that support forest regeneration.^[52] The small, hard seeds embedded in sweet, fleshy fruits facilitate passage through digestive tracts with minimal damage, enhancing germination potential.^[50] In introduced ranges, dispersal is amplified by invasive mammals like rats and feral pigs, which consume fruits and promote rapid colonization, contributing to the invasive success of species such as P. guajava.^[53] Each fruit contains hundreds of seeds, enabling high dispersal efficiency and establishment rates in suitable disturbed habitats.^[4] Human activities, including transport via trade and waste, further accelerate spread in non-native areas, often outpacing natural vectors.^[50]

Biotic Interactions

Psidium species engage in various biotic interactions that influence their ecological roles and ecosystem dynamics. Herbivory on Psidium plants primarily targets leaves and fruits, with insects such as the guava fruit fly (Bactrocera correcta) infesting developing fruits and causing significant damage by larval feeding, rendering them unmarketable.^[54] Other insect herbivores include the Caribbean fruit fly (Anastrepha suspensa), fruit moths, whiteflies, red-banded thrips, mealybugs, and scales, which feed on foliage, sap, and fruits, potentially reducing plant vigor.^[55] Mammalian herbivores, including bats, monkeys, rats, and feral pigs, consume fruits and occasionally leaves, contributing to seed dispersal while exerting pressure on plant populations in natural settings.^[4] To counter these threats, Psidium species produce chemical defenses, such as essential oils rich in sulfur volatiles like dimethyl disulfide in wounded leaves, which exhibit toxicity against insects and deter further herbivory.^[56] Symbiotic relationships in Psidium enhance nutrient acquisition in nutrient-poor soils. Arbuscular mycorrhizal fungi (AMF), such as Glomus mosseae, form associations with Psidium roots, extending hyphal networks to improve uptake of phosphorus and other minerals from soil, thereby promoting plant growth and establishment.^[57] These mycorrhizae increase root surface area and facilitate transfer of nutrients like magnesium, copper, and molybdenum to the host, while the plant provides carbohydrates in return.^[58] Additionally, endophytic nitrogen-fixing bacteria, including diazotrophs, colonize Psidium tissues and contribute to biological nitrogen fixation, boosting soil fertility and plant nutrition when applied as biofertilizers.^[59] As invasive species, Psidium plants, particularly P. cattleyanum (strawberry guava), profoundly alter ecosystems in introduced regions like Hawaii and other Pacific islands. They outcompete native flora by forming dense monospecific stands that shade out understory vegetation, reducing biodiversity and modifying forest structure.^[60] This invasion disrupts nutrient cycling and fire regimes, leading to long-term degradation of native habitats and hindering regeneration of endemic species.^[61] In Hawaiian forests, P. cattleyanum can dominate the canopy in affected areas, exacerbating soil erosion and altering hydrological processes.^[62] Within food webs, Psidium serves as a vital resource for multiple trophic levels. Fruits provide nourishment for frugivores, including birds, bats, and mammals like rats and pigs, supporting their energy needs and facilitating seed dispersal across landscapes.^[4] Pollen from Psidium flowers acts as a food source for hymenopterans, such as bees, integrating the genus into pollinator networks and enhancing community interactions in tropical ecosystems.^[20]

Conservation Status

The genus Psidium encompasses approximately 92 species, the majority of which are assessed as Least Concern on the IUCN Red List due to their wide distributions and adaptability, particularly P. guajava, which faces no major documented threats despite ongoing deforestation in parts of its native range. However, several endemic species in the Caribbean islands are classified as Vulnerable, Endangered, or Critically Endangered, primarily owing to severe habitat loss; for instance, Psidium sintenisii is Critically Endangered in Puerto Rico, while Psidium amplexicaule is Endangered across the Greater Antilles.^[63][64] Key threats to Psidium species include deforestation for timber and land conversion, expansion of agriculture into native tropical and subtropical forests, and competition from invasive alien species that alter native habitats and reduce available resources in their ranges.^[65] These pressures are especially acute for Caribbean endemics, where habitat fragmentation from development exacerbates vulnerability, and for Atlantic Forest species in Brazil, where approximately 25% of original forest cover remains.^[66] Conservation efforts for Psidium focus on in situ protection through designated areas, such as Brazil's Floresta Nacional do Araripe and Parque Nacional do Ibiapaba, which safeguard populations of rare and endemic species like Psidium revolutum amid ongoing habitat threats in the Atlantic Forest.^[67] Ex situ conservation complements these measures via living collections and seed banking in botanic gardens worldwide, preserving genetic material for species like P. sintenisii and supporting potential reintroductions. Wild populations of P. guajava exhibit notable genetic diversity, yet there are growing concerns over erosion due to widespread cultivation, which promotes hybridization with domesticated varieties and potential displacement of native genotypes in remnant habitats.^[68] Studies using microsatellite markers highlight the need to prioritize wild germplasm collection to maintain this diversity for future breeding and restoration.^[69]

Cultivation and Uses

Cultivation Practices

Psidium species, particularly P. guajava, are propagated through both sexual and vegetative methods to ensure genetic fidelity and disease resistance in commercial cultivation. Seeds are sown in nurseries under shaded conditions with well-drained soil, germinating in 2-3 weeks at temperatures of 25-30°C, though this method results in variability and longer time to fruiting (up to 4-5 years). Vegetative propagation, preferred for uniformity, includes air-layering, which involves wounding branches and applying rooting hormones like IBA before wrapping in moist medium, achieving 70-80% success in humid environments; grafting techniques such as inarching or budding onto seedling rootstocks; and stooling, the cheapest method where shoots are layered around the base of mature trees in moist soil. Optimal nursery conditions include partial shade, regular misting, and sterile media to prevent fungal issues, with plants ready for transplanting after 6-12 months.^{[70][71][72][73]} In field cultivation, Psidium guajava trees are spaced 4-6 meters apart in rows to optimize light penetration and airflow, accommodating their growth to 6-10 meters tall while facilitating mechanical harvesting. Irrigation is essential during dry seasons, with young trees requiring 20-40 liters per plant weekly, tapering to drip systems delivering 500-800 mm annually for mature orchards to maintain soil moisture without waterlogging, as guavas tolerate drought but yield declines by 30-50% under stress. Pruning is conducted annually post-harvest to shape the canopy into an open center, removing deadwood and water sprouts to enhance fruit quality and yield, with initial training in the first 3-4 months after planting promoting a strong framework. Fertilization follows soil tests, typically applying 200-300 g NPK per tree yearly, split into doses to support vegetative growth and flowering.^[46][74][75] Commercial cultivation emphasizes cultivars selected for fruit quality, disease resistance, and market demand, with P. guajava varieties like 'Ruby Supreme' prized for its large, sweet, pink-fleshed fruits with few seeds and high vitamin C content, maturing in 10-15 foot trees suitable for subtropical climates. Pest management focuses on integrated strategies against fruit flies (Anastrepha spp.), including sanitation by collecting and destroying fallen fruits, deployment of methyl eugenol traps at 25 per hectare to monitor and mass-trap adults, and bait sprays with protein hydrolysate plus insecticides applied every 7-10 days during fruiting; cultural practices like bagging fruits with paper bags further reduce infestation by 80-90%. These approaches minimize chemical use while protecting yields.^{[76][77][78][79]} As of 2023, global guava production is estimated at approximately 12 million metric tons, dominated by India with about 5.59 million metric tons (over 45% share), followed by China (around 3.5 million tons), Indonesia (3.6 million tons), and smaller producers like Pakistan, Brazil (0.34 million tons), and Mexico (0.25 million tons). Yields under optimal management reach 20-30 tons per hectare, though averages in India hover at 15 t/ha due to varietal and climatic factors. India cultivates guava on approximately 0.36 million hectares.^{[80][81][82][83]}

Economic and Culinary Uses

Psidium guajava serves as the primary economic species within the genus, with its fruits widely consumed fresh for their distinctive sweet-tart flavor and aromatic profile. The fruits are also processed into a variety of culinary products, including juices, jams, jellies, preserves, desserts, and the traditional guava paste known as dulce de guayaba in Latin American cuisines.^[4] These applications leverage the fruit's versatility, making it a staple in both household and commercial food preparation across tropical regions.^[84] Among other Psidium species, Psidium cattleyanum, commonly known as strawberry guava, has minor economic and culinary roles, primarily through its ornamental fruits that are eaten fresh or incorporated into beverages, jams, and desserts. Its smaller-scale production contrasts with the dominant commercial focus on P. guajava, though it contributes to niche markets in ornamental horticulture and local food products.^[85][86] The global guava market, driven largely by P. guajava, was valued at approximately USD 7.2 billion in 2023 and is projected to grow to USD 13.0 billion by 2033, reflecting increasing demand for fresh and processed forms. International trade in fresh guava reached an estimated 330,000 tonnes in 2020, with major exports from Mexico to North America in the mango-guava cluster valued at USD 519 million that year (guava comprising ~15% of the volume). Cultivation provides essential income in countries like India, Brazil, and Mexico, where it ranks among top fruit crops and sustains rural economies through high yields and diverse product lines.^{[87][88][89][90]} Nutritionally, P. guajava fruits are renowned for their high content of vitamin C (228 mg per 100 g, exceeding four times the daily value), dietary fiber (5.4 g per 100 g), and antioxidants such as lycopene, quercetin, and other flavonoids, which enhance their appeal in health-oriented foods. These nutrients are retained in processed forms like purees, powders, and concentrates, which are used in functional beverages, supplements, and baked goods to extend shelf life and broaden market reach.^[91][92]

Medicinal and Other Uses

Psidium guajava, commonly known as guava, has been utilized in traditional medicine across various cultures for its therapeutic properties. In indigenous American systems, such as those in Mexico and among Mayan communities, decoctions and infusions of leaves and bark are commonly employed to treat diarrhea, dysentery, stomachache, coughs, and wounds, with applications including oral consumption for gastrointestinal issues and topical use for skin ailments.^[93] Similarly, in Ayurvedic medicine, guava leaves are used for managing respiratory conditions like coughs, gastrointestinal disorders including dysentery, and wound healing, often prepared as teas or poultices to leverage their astringent and anti-inflammatory effects.^[94] These traditional practices highlight the plant's role in folk healing, particularly for digestive and respiratory ailments, supported by ethnobotanical records from regions like Latin America and India.^[95] Modern pharmacological studies have validated several of these uses, focusing on the plant's bioactive compounds. Leaf extracts exhibit antidiarrheal and antidiabetic potential, with compounds like quercetin and flavonoids inhibiting enzymes such as α-glucosidase and reducing blood glucose levels in animal models, suggesting benefits for diabetes management.^[96] Fruits and leaves demonstrate anti-inflammatory effects, attributed to phytochemicals including quercetin (typically 1-5 mg/100g in fruit, higher in leaves up to ~18 mg/100g dry extract) and triterpenoids like oleanolic acid, which reduce markers such as TNF-α in conditions like osteoarthritis.^[96][97] Clinical trials, including one involving 137 patients, confirm the efficacy of leaf extracts in treating diarrhea through antibacterial and antimotility actions.^[95] Guava consumption is unlikely to contribute to non-alcoholic fatty liver disease (NAFLD) due to its favorable nutritional profile. It provides approximately 68 kcal per 100g, contains high levels of dietary fiber (about 5.4g per 100g), and has a low glycemic index (12-31), which aids in blood sugar control and may help reduce insulin resistance—a key risk factor for NAFLD.^[91][98][99] No studies indicate guava as a risk factor for NAFLD; in fact, research on guava leaf extracts has demonstrated potential benefits in suppressing hepatic metabolic alterations and alleviating fatty liver in animal models, contrasting with established risk factors such as excess caloric intake, obesity, added sugars, and metabolic syndrome.^[100][101] Beyond medicinal applications, Psidium guajava serves ornamental purposes in landscaping due to its evergreen shrub form and attractive foliage, often planted in tropical gardens for aesthetic appeal.^[102] The wood, yellowish to reddish in color, is utilized for crafting tool handles, fence posts, and carpentry items, owing to its durability and resistance to insects and fungi, and it also provides high-quality firewood and charcoal.^[103] Environmentally, the plant aids in erosion control and serves as live fences or windbreaks in agricultural settings, while offering shade and supporting biodiversity in tropical ecosystems. Regarding safety, guava is generally considered non-toxic at typical doses, with acute toxicity studies in rodents showing a median lethal dose exceeding 5 g/kg body weight and no genotoxicity observed.^[104] However, high doses of bark extracts (over 1,000 mg/kg) may cause mild organ toxicity, and seeds, while edible, can pose a choking hazard due to their hardness.^[93] Use during pregnancy lacks sufficient safety data, with recommendations for caution as medicinal preparations may have unknown effects, though moderate fruit consumption as food is likely safe.^[104] Global production of the mango-guava-mangosteen cluster is projected to reach 86 million metric tons by 2034 (OECD-FAO, 2025), with guava's share growing amid rising demand for nutrient-rich tropical fruits.^[105]

Species

Species Diversity

The genus Psidium comprises 78 accepted species according to the Plants of the World Online database, though estimates including synonyms and recently described taxa range up to 150 species.^[2][84] Brazil represents the primary center of diversity and endemism for the genus, hosting over 50 species, many of which are restricted to its biomes such as the Atlantic Forest and Cerrado.^[1][106] The diversification of Psidium reflects a Neotropical radiation, with species distributed from Mexico southward to northern Argentina and the West Indies, originating around 25 million years ago and driven by ecological adaptations including polyploidy and apomixis.^[1] Morphological variation is pronounced across the genus, particularly in fruit characteristics such as size (ranging from 8 to 60 mm in diameter) and color (from green and yellow to crimson), as well as in leaf traits including pubescence, size (0.4–19 cm), and venation patterns (brochidodromous to camptodromous).^[1] These variations contribute to the adaptive success of Psidium in diverse habitats from dry forests to montane regions. Infrageneric classification recognizes four major monophyletic sections based on phylogenetic clades and associated habits: Section Psidium (10 species, including arborescent forms like P. guajava), Section Obversifolia (6 species, often fruticose shrubs), Section Apertiflora (31 species, with hemiepiphytic tendencies), and Section Mitranthes (26 species, typically small trees or shrubs).^[1] These groupings highlight shifts in growth form, from arborescent trees in more open environments to fruticose or scandent shrubs in forested understories. Taxonomic challenges persist due to widespread hybridization—such as between P. guajava and P. guineense—and morphological overlap, leading to unresolved species complexes and uncertain status for approximately 35 taxa.^[1] High levels of homoplasy and convergence further complicate delimitation, particularly in regions of sympatry like eastern Brazil.^[1]

Notable Species

Psidium guajava, commonly known as the common guava, is a shrub or small tree reaching up to 10 meters in height, native to tropical regions from Mexico to northern South America, and now widely distributed pantropically through cultivation.^[4] Its round to ovoid fruits, typically 5-10 cm in diameter, are highly edible with a sweet, aromatic flesh rich in vitamin C, making it a staple in tropical agriculture and cuisine.^[4] However, P. guajava has invasive potential in disturbed habitats, forests, and waterways, where it forms dense thickets that outcompete native vegetation in areas such as Hawaii, the Galápagos Islands, and parts of South Africa.^[107] Psidium cattleianum, or strawberry guava, is a small evergreen tree or shrub growing 2-6 meters tall, originating from southeastern Brazil, southeastern Paraguay, and northern Uruguay, and introduced widely to subtropical and tropical regions.^[108] It produces small, spherical red or yellow fruits about 2-4 cm in diameter, which are edible with a strawberry-like flavor and often used ornamentally or for fresh consumption.^[108] Valued for its attractive foliage and fruits, it is highly invasive in Pacific islands, Florida, and Hawaii, where it creates monotypic stands that shade out understory plants and facilitate pest spread, such as fruit flies.^[108] Psidium friedrichsthalianum, the Costa Rican guava, is a small evergreen tree up to 8 meters high with a straight bole, native to wet tropical forests from southern Mexico through Central America to northern South America.^[109] Its yellow, aromatic fruits, 3-5 cm in diameter, are sour and primarily used locally for beverages like fresco de cas, jams, and as a source of antioxidants with anti-inflammatory properties in traditional medicine.^[109][110] Psidium guineense, known as Brazilian guava or Guinea guava, is a shrub or small tree 1-5 meters tall, distributed from Mexico through Central America to tropical South America, with some naturalized populations in Africa and Asia.^[111] The small, acidulous fruits are edible and suitable for jellies or preserves, while the leaves are employed in folk remedies for gastrointestinal issues like diarrhea and stomachaches.^[111] It serves as a wild relative for rootstock in guava cultivation but can become weedy in disturbed areas.^[111] Psidium sintenisii, or Sintenis' guava, is a rare small evergreen tree endemic to moist forests in western Puerto Rico, classified as critically endangered due to habitat loss and limited distribution in only three protected areas.^[63][112] Its fruits are lesser-known but align with genus traits of small, edible berries, though conservation efforts prioritize its survival over utilization.^[112] Among these species, fruit edibility varies significantly: P. guajava offers the largest, sweetest fruits for broad consumption, while P. cattleianum and P. guineense provide smaller, more acidic options suited to processing, and P. friedrichsthalianum emphasizes medicinal value over direct eating.^{[4][108][109]} Habitat preferences differ as well, with P. guajava and P. cattleianum thriving in diverse, often disturbed tropical lowlands and showing invasive tendencies, contrasted by the forest-restricted, non-invasive niches of P. friedrichsthalianum and the endangered P. sintenisii in montane or wet environments.^[63][111]