Botanical Characteristics of Taiwanese Guava, Dien Grapefruit, Vinh Orange

Weaning combined with drinking "guava tea" is a very popular way of eating in South America as a food-medicine in the polluted era.

b- Parts of guava, orange, grapefruit trees used as medicine

Parts of guava, orange, grapefruit trees such as young buds, young leaves, fruit, root bark and trunk bark are all used as medicine.

Folk remedies from guava, orange, grapefruit trees are used in Vietnam, China, Hawaii, Central America, South America, Caribbean, West Africa...

Pharmacological studies show that extracts of guava tree parts have antibacterial properties, astringent mucosa and antidiarrheal properties.

c-Other uses of guava, orange, grapefruit

-In the past, in Vietnam, rural people used guava wood to make millstones, pepper pestles, wedge shafts, plow yokes, boat oar masts, etc.

-In foreign countries, guava bark is used in the tanning process thanks to its high tannin content.

-In Hawaii, guava, orange, and grapefruit wood is used as firewood for grilling meat, and guava wood is used as charcoal at barbecue competitions across the United States because the smoke from the tree is non-polluting and enhances the flavor of the grilled meat.

-Guava, orange, and grapefruit essential oils are used in various shampoo products in several countries due to their pleasant scent.

-In India and East Asia, guava trees are shaped into ornamental trees and Bonsai has become popular.

- Grapefruit leaves are often used to boil with other aromatic leaves to treat colds and headaches.

- Grapefruit peel treats indigestion, stomachache, or to cook grapefruit tea.

- Grapefruit seed peel can be extracted to get pectin as a hemostatic medicine and used as hair gel.

- Grapefruit juice is used as a medicine to treat diabetes and vitamin C deficiency.

- Grapefruit seed charcoal powder can be used to treat impetigo in children.

2.3. Botanical characteristics of Taiwanese guava, Dien grapefruit, Vinh orange

2.3.1. Botanical characteristics

* Brief description of Taiwanese guava tree

Guava tree is a small tree, perennial, can live up to 60-70 years.

- Trunk: The trunk has many branches, 4-6 m high, the tallest is 10 m, maximum trunk diameter is 30 cm. New varieties are even smaller and shorter. The trunk is strong, healthy, short because of early branching. The trunk is smooth and rarely gets bored by insects, the old bark can peel off in pieces, underneath there is a new layer of bark that is also smooth, gray, slightly green. Young branches have 4 sides, gradually rounding when old.

-Leaves: Leaves are simple, opposite, without stipules. Leaf blade is oval, base is rounded, tip has thorns or convex, 11-16 cm long, 5-7 m wide, upper surface is darker green than lower surface. Blade edge is intact, young leaves have purple-pink border extending to the petiole. Leaf veins are pinnate, midvein is prominent on the lower surface, 14-17 pairs of secondary veins. Leaf petiole is green, cylindrical, 1-1.3 cm long, with shallow grooves on the upper surface

-Flowers: Large, bisexual, ovary inferior, growing in clusters of 2, 3, rarely at the top of the branch but usually in the leaf axils. Flower pattern 5, bracts are regular leaves, bracts are scaly, 3-4 mm long, slightly brownish green. Peduncle 1.4-2.6 cm long, green. Receptacle shaped like a cup, 0.8-1.2 cm long, green. Calyx adheres to a whole tube, when the flower blooms it separates into 4-5 uneven lobes, green on the outside, white on the inside, valved. Petals 5, nearly even, separate, thin white, easy to fall off when the flower blooms, oval blade curved at the top, 1.4-1.6 cm long, 0.6-0.8 cm wide, outer surface with many fine hairs, with 3-5 veins, small curved nail with fine yellow hairs, five-pointed precolumn. Stamens: many separate, uneven, attached in many rings on the flower receptacle; filaments flat white, pale yellow base, 7-14 mm long, hairy; anthers yellow, 2-celled, longitudinally dehiscent, attached at base; pollen grains loose, small, obtuse triangular at tip, 17-20 µm long, yellow-brown with 3 holes. Carpels 5, adherent, ovary inferiorly 5-celled, each cell many-ovules, ovules centrocytosed. Style 1,

White filaments slightly swollen at the base, with many fine hairs, 1-1.2 cm long. Stigma 1, green, disc-shaped.

Flowers cross-pollinate easily but can also self-pollinate.

- Fruit: Round, oval or pear-shaped, 3-10 cm long depending on the variety. The young fruit skin is green, turning yellow when ripe, the fruit skin flesh is white, yellow or red. The pulp is white, yellow or red. Inside the fruit there are many seeds covered in a spongy mass. Ripe fruit has a sweet and sour taste or sweet and has a characteristic aroma, can be eaten fresh, made into jam or soft drinks. When ripe, the fruit is easily eaten by birds, bats, and squirrels, which spread the seeds.

-Seeds: Many seeds, yellow-brown, polygonal, hard shell and located in white, pink, red-yellow flesh. From pollination to fruit ripening is about 100 days.

It is a popular fruit tree, grown almost everywhere, both in the plains and in the mountains, except for the highlands above 1500m. The tree loves light and grows well in tropical and subtropical climates. Temperature range is from 15-45 o C, the best temperature for the tree to grow and produce many fruits is from 23-28 o C; rainfall is 1000-2000 mm/year. Guava flowers and fruits many years. Inflorescences often appear on new branches that grow in the same year. Pollination is by wind or insects. Life cycle can last 40-60 years. Flowering season: March-April; fruiting season: August-September.

* Brief description of the Orange tree:

Vinh oranges have a very thin peel, the segments inside are light yellow, when eaten, the fruit has a sweet taste, some fruits also have a slightly sour taste.

- Orange trunk and branches: The trunk is woody, semi-shrub type, has 4-6 main branches, the tree is 2-3m high, low branching. The branches are directed towards the top, sparse, and branch horizontally.

- Orange leaves: Leaves grow alternately, long blade, dark green, oval, 5-10cm long, 2.5-5cm wide, edges have sparse teeth; petiole has slightly wings, 4-10mm wide. Leaves have small ears.

- Orange flowers: Short flower clusters in leaf axils, solitary or in groups of 2-6 flowers in clusters; cup-shaped calyx, hairless; white petals 1.5-2cm long; 20-30 stamens fused together into 4-5 bunches.

- Orange roots: Like woody dicotyledonous plants, the roots are of the type that absorb water and minerals for the plant. The shallowly distributed and strongly developed root system is adventitious, widely distributed and thick in the topsoil layer and prefers loose soil. The root system develops most strongly in February and September, the root system develops strongly in the first 8 years.

* Brief description of Grapefruit tree

- Pomelo tree trunk: Large tree 5-10m tall, young shoots have soft hairs, branches have small thorns up to 7cm long.

- Pomelo leaves: Leaves are broad oval, rounded at the base, with entire edges, with joints on the petiole; petiole has wide wings.

- Grapefruit flower: Inflorescence in leaf axils, including 7-10 large, white, very fragrant flowers.

- Grapefruit: Large, spherical and flat, 15-30cm in diameter, yellow or pink depending on variety.

The tree flowers and bears fruit almost all year round, mainly from March to May and from August to November.

2.3.2. Ecological characteristics of Guava, Grapefruit, Orange trees

* Ecological characteristics of Guava tree

Guava is a popular fruit tree, grown almost everywhere, both in the plains and in the mountains, except for highlands above 1500m.

Guava trees are suitable for an average annual temperature of 25 - 27 0 C. Guava trees cannot withstand cold, compared to oranges, guava is less resistant to cold, but compared to papaya and banana, guava is much better. At a temperature of -20 0 C, even large trees will die. On the contrary, guava can easily withstand high temperatures in deserts if there is enough water. Low temperatures, for example below 18 - 20 0 C, produce small fruit, slow growth, and poor quality (Tran The Tuc, 1999) [3].

Guava likes humid climate, if annual rainfall is 1,500 - 4,000 mm and relatively evenly distributed, watering is not required. Guava root system adapts well to changes in weather.

Sudden changes in soil moisture. If there is a drought and the groundwater level is low, guava can quickly develop some vertical roots that penetrate deep into the ground up to 3-4 m or more. If there is a lot of rain and the water level rises, guava will grow many roots that grow back into the ground so it does not suffocate. Even if it is completely flooded for a few days, guava will not die. This feature can be used to actively control the groundwater by irrigation to allow the roots to grow shallowly in the fertile topsoil.

Guava is suitable for many types of soil, with a suitable pH of 4.5 - 8.2. Guava grows well on alluvial soil, rich in organic matter, red basalt soil, and can be grown on raised and improved alum soil or on nutrient-poor soil but provided with plenty of organic fertilizer. However, to achieve high yield of guava, good, deep soil must be selected and fertilized properly.

Guava is not afraid of wind but the large fruit and large leaf varieties will tear and fall off when caught in storms. So plant in a sheltered place or as a windbreak.

Guava flowers and fruits many years. Inflorescences usually appear on new branches that emerge in the same year. Pollination is by wind or insects. Life cycle can last 40 – 60 years.

* Ecological characteristics of grapefruit trees

- Grapefruit trees have a very high demand for water, especially during the flowering and fruit development period. On the other hand, grapefruit trees are also very sensitive to waterlogging conditions. During the rainy season, if the groundwater level in the soil is high and does not drain in time, the tree will rot, the leaves will turn yellow and die. Grapefruit is suitable for fertile soil with a thick cultivation layer of 0.5-1 m, loam soil, good drainage, ventilation, pH from 5-7.

* Ecological characteristics of Vinh orange tree

Oranges can be grown in areas with temperatures ranging from 12 to 39 degrees Celsius, with the most suitable temperature being from 23 to 29 degrees Celsius. Temperatures lower than 12.5 degrees Celsius and higher than 40 degrees Celsius will cause the plant to stop growing. In general, temperature is a very important factor, affecting all life activities of the plant as well as the yield and quality of the fruit.

It is a moisture-loving plant but cannot tolerate waterlogging because the roots of oranges are mycorrhizal (absorbing nutrients through a symbiotic fungal system), so if the soil is flooded

Lack of oxygen will cause the roots to function poorly, and if flooded for a long time, they will rot and die, causing leaves and young fruit to fall off. This explains why citrus trees grown on flat land do not have a long life span compared to trees grown on sloping land.

Vinh oranges can be grown on many types of soil, however, they are most suitable for growing on humus-rich soil, with nutrient content of NPK, Ca, Mg... at an average level or higher, suitable pH is 5.5 - 6.5, mechanical composition of sandy loam or light loam, good drainage.

2.4. Research situation at home and abroad

2.4.1. Research and production situation of guava, grapefruit, orange in the world

* Guava production situation in the world:

In the world, fruit trees have been paid attention to for a long time, are a unique and important agricultural product in export in many countries around the world. For example: China is famous for jujube; India, Thailand export mango; Spain, Italy, Brazil, Egypt ... export oranges, lemons, tangerines; Ecuador exports bananas, Thailand, Keenia, Nigeria export pineapples ... earning a huge amount of foreign currency, contributing significantly to the economic development of those countries (Tran Nhu Y et al., 2000) [4].

Guava is a tropical fruit tree, according to Ortho (1985) the guava improvement program started in 1961 in Colombia and Brazil (Ortho,1985) [10].

In Mexico, guava is one of the most important crops with a large annual area of 14,700 hectares and a fruit production of 192,850 tons. Only in recent years have research programs been initiated to identify productive guava varieties for cultivation and other related fields.

India is the world's leading fruit producer with an annual production of 32 million tonnes, accounting for 8% of the world's fruit production. According to the Technical Information Assessment and Forecasting Council (TIFAC), India currently has eight world-famous products: mango, banana, mandarin, apple, papaya, guava, pineapple and grapes. Of these, guava occupies an area of 228,500 hectares with a production of 2.61 million tonnes. The Allahabad region in UP is reputed for producing high quality

of guava in India and the world. In Punjab it occupies an area of 8022 ha, with an annual production of 160,463 tonnes (Singh et al., 2007) [12].

* Grapefruit production situation in the world

The total world grapefruit output is about 6.5 million tons, of which both grapefruit ( Citrus paradisi ) and grapefruit ( Citrus grandis ) account for 5.4 million tons.

- 5.6% of total citrus output. Grapefruit production is mainly concentrated in the Americas and Europe for juice processing. Grapefruit is mainly produced in Asian countries, concentrated in some countries such as China, India, Philippines, Thailand, Bangladesh,... and is mainly used for fresh consumption.

Table 2.1 Area, yield and production of grapefruit in the world

Target

Year
2012	2013	2014	2015	2016	2017
Area (ha)	321,528	322,898	348,689	354,625	358,724	444,072
Yield (tons/ha)	256,302	264,608	249,112	49,149	252,937	310,700
Output (tons)	8,240,840	8,491,232	8,686,264	8,835,434	9,074,176	13,795,429

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(Source: FAOSTAT, 2019)

According to the data in Table 2.1, as of 2017, the area of grapefruit trees in the world reached 444,072 hectares, the average yield reached 310.7 quintals/ha and the output reached 13,795,429 tons. Within 5 years from 2012 - 2017, the area did not increase much but the output increased by more than 4.7 million tons, mainly due to the increased productivity due to the application of scientific and technological advances in grapefruit production.

Through the data in table 2.2, statistics in table 2.3 show that in 2017, China was the country with the largest grapefruit area in the world, reaching 95,861 hectares, the highest productivity in the world (493.8 quintals/ha) and an output of 4,733,447 tons of fruit.

Table 2.2. Area, yield and output of grapefruit in some major grapefruit growing countries in the world in 2017

Region/location	Acreage	Power	Output
1	World	444,072	310.7	13,795,429
2	Africa	58,817	138.4	813,910
3	America	73,842	210.3	1,552,658
4	Asia	301,827	365.9	11,042,350
5	Europe	8,697	435.0	378,336
6	Asia	889	92.0	8,175
7	China	95,861	493.8	4,733,447
8	America	24,440	259.1	633,210
9	Mexico	17,709	249.5	441,873
10	Brazil	4,544	177.9	80,852
11	Thailand	26,059	188,610	230,909
12	India	16,850	231,748	390,500
13	Vietnam	46,791	121.50	568,352

(Source: FAOSTAT, 2019)

* Orange production situation in the world

Over the past decades, the productivity, area and output of citrus have been increasing rapidly. The citrus growing belt stretches from 40 0 North latitude to 40 0 South latitude, which means that citrus are only grown in tropical and subtropical regions. Currently, tropical fruit growing regions such as Vietnam, Cuba, Thailand, Malaysia and Southern China bordering Vietnam are facing great difficulties in developing citrus due to some typical tropical diseases, such as greening disease. The destructive power of these diseases has caused the citrus acreage of some countries in the tropics to shrink or not increase. On the contrary, the subtropical climate does not allow typical citrus diseases, such as greening disease, to develop strongly, so citrus in tropical regions tends to develop strongly in terms of area, productivity, fruit quality as well as investment in technical measures for varieties and cultivation.

According to FAO data in 2018

Today orange trees are grown across continents, the development of

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