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The Mother Nature bestowed humanity with about 250,000 known plant species and perhaps the same or may be higher number of unknown plant species. Out of this treasure, 80,000 plant species are edible but human beings have probably exploited about 3,000 of these species for food and was cultivating about 150 on a commercial scale. However, largely human beings consumed only 20 different kinds of crops the world over and four of which viz. rice, wheat, maize and potato are supplying about 60 % of total calories. Under the circumstances, the food crops base even for well-known crops are shrinking at an alarming rate and in this process, many species have extincted from man’s food bowl. While doing so, we have considerably reduced the range of organic compounds that we now consume, thus making ourselves vulnerable to various stresses. Realising  importance of diverse food base in our life, thinking is going on among people of all lifestyles that more and more crops particularly those, which are known to be edible but have remained as “under-utilised crops”, should be brought into cultivation. This will ensure both food and nutritional security of people. Among these, tuber crops constitute an important crops group, which was sustaining food security much before agriculture came into existence.

Malvaceae, the mallow family, carries herbs, shrubs or trees comprising about 75 genera and perhaps as many as 1,500 species. Hibiscus and Abelmoschus are two important genuses under this plant family. Several species of plants of potential uses come under these two genera about which limited publications are available. 

Hibiscus

Hibiscus is a large genus of about 200-220 species of flowering plants in  Malvaceae, native to warm temperate, subtropical and tropical regions throughout the world. The genus includes both annual and perennial herbaceous plants and woody shrubs and small trees. The leaves are alternate, simple, ovate to lanceolate, often with a toothed or lobed margin. The flowers are large, conspicuous, trumpet-shaped, with five petals, ranging from white to pink, red, purple or yellow, and from 4-15 cm broad. The fruit is a dry five-lobed capsule, containing several seeds in each lobe, which are released when the capsule splits open at maturity.

Common names:  Sessile joyweed, Joyweed, Dwarf copperleaf (English), Geluti (Hindi), Ponnanganni green (Tamil) Latin names: Alternanthera sessilis (L) Syn: Alternanthera nodiflora R. Br., Gomphrena sessilis (L), llecebrum sessile (L) Linnaeus belongs to family Amaramlnaceaes.

Habit and Habitat
 
Perennial herbs, pantropical, damp shady areas, swamps, pond margins, shallow ditches, road sides, low-lying waste lands, damp pastures, cultivated areas. In New Guinea, «a plant of damp places; ditches, wet headlands, roadsides; sometimes a weed of plantations, particularly at altitudes of 1500 m or higher. From near sea level to over 2000m» (Henty & Pritchard, 1975). In Tonga, «occasional as a waste area weed» (Yuncker, 1959).

The Cucurbitaceae family consists of nearly 100 genera and over 750 species. Although most of them have Old World origin (Whitaker and Davis, 1962), many species originated in the New World and at least seven genera have origins in both hemispheres (Esquinas-Alcazar and Gulick, 1983). There is considerable genetic diversity within the family and the range of adaptation for cucurbit species includes tropical and subtropical regions, arid deserts and temperate locations. A few species are adaptable to production at elevations as high as 2000 m. The genetic diversity in cucurbits extends to both vegetative and reproductive characteristics. There is considerable range in the monoploid (x) chromosome number (Jeffrey, 1990) including 7 (Cucumis sativus), 11 (Citrullus spp., Momordica spp., Lagenaria spp., Sechium spp., and Trichosanthes spp.), 12 (Benincasa hispida, Coccinia spp., Cucumis spp. other than C. sativus, and Praecitrullus fistulosus), 13 (Luffa spp.), and 20 (Cucurbita spp.).
 
Archaeological evidence indicated that cucurbits were present in ancient and prehistoric cultures. Lagenaria was associated with man as early as 12,000 BC in Peru (Esquinas-Alcazar and Gulick, 1983). Archaeological expeditions in the Oaxaca region of Mexico have reported that Cucurbita pepo was associated with man as early as 8500 BC and cultivated by 4050 BC (Esquinas-Alcazar and Gulick, 1983). Written Chinese records describing the use of cultivated cucurbits have been found as early as 685 BC (Herklots, 1972).

Indian arid zone is one of the largest sub-tropical deserts of the world, of which 20 % is arid and the remaining semi-arid with varied habitats. The hot arid region is spread over 31.7 million ha mainly in Rajasthan (19.6 m ha), Gujarat (6.22 m ha), Andhra Pradesh, Punjab and Haryana. Rajasthan is the largest state in the country covering approximately 34.2 m ha geographical area out of which 27.1 m ha (79.08 % of total area) is laying in arid and semi-arid climate, spread over 21 out of 32 districts. Western part of Rajasthan is under hot arid climate (Thar Desert) and it extends from 24^º 37’ to 30^º 10’ N latitude and 690 29’ to 76^º 05’ E longitude. Barmer, Bikaner, Churu, Ganganagar, Hanumangarh, Jaisalmer, Jalore, Jhunjhunnu, Jodhpur, Nagour, Pali and Sikar districts of Western Rajasthan account for 63.4 % area of  hot arid realm of India. Apart from these, about 10 % area each of Sirohi, Ajmer and Jaipur districts are also in arid region. Punjab and Haryana bound it in North and Gujarat in South. The Aravali hill ranges provide a natural boundary with semi-arid Eastern Rajasthan. In the West, it has a long international boundary with Pakistan.

The Cucurbitaceae family is characterized by long training viny stems. There is variation for flower size and colour among the species but all of them have similar general morphology. The species are open pollinated and self compatible. Most of them are either monoecious (eg. Cucurbita spp.) Or andromonoecious (e.g. common in melon). Other species show gynomonoecy, androgynomonoecy, androecy, gynoecy, hermaphrodite or dioecy. Chow-chow is the only member of the Cucurbitaceae that is viviparous, contains single seed and propagated by planting whole fruit. The Indian gene centre has rich diversity in genetic resources of ridgegourd (Luffa acutangula), bottlegourd (Lagenaria siceraria), bittergourd (Momordica charantia), ashgourd (Benincasa hispida), snakegourd (Trichosanthes anguina), pointed gourd- parval (Trichosanthes dioica), pumpkin (Cucurbita spp.) and roundgourd (Praecitrullus vulgaris). Cucurbits are of tremendous economic importance and are cultivated throughout the world from tropical to sub-temperate zones. China, Turkey, India and Iran are important cucurbit growing countries. In India, this diversity is concentrated in Indo-Gangatic plains, north eastern region, north western Himalayas, the Western and Eastern Ghats and sporadically in the tribal dominant belts of central India.  More diversity occurs in Cucurbita spp. in the north east as also for ashgourd, bottlegourd while for Luffa, it is more concentrated in the eastern peninsular tract.

Ber (Chinese date, Chinese fig or bore) (Ziziphus xylopyrus) is an important minor fruit of India. It is a hardy fruit tree cultivated all over India and also known as poor man’s fruit. It is widely cultivated in Punjab, Haryana, Rajasthan, Uttar Pradesh, Madhya Pradesh, Bihar, Gujarat and Maharashtra. Ber does well even under marginal growing conditions and provides quality yields at low cost (Shukla, 1996). Fruits are eaten fresh but the other forms like dried, candied and squash can also be prepared from ber. Stem bark, root and leaves have medicinal values. Leaves of ber are used as fodder in dry regions. Ber tree is a host plant for rearing the Tachardia laccad, a lac insect (Sharma and Kore, 1990).

Plant genetic resources are the key components of crop improvement because of development of precision breeding system through biotechnological approaches as well as conventional system of breeding like selection and hybridization. Breeding system of hybridization is replaced by cybrid technology that facilitates transferring more qualitative and quantitative traits rapidly within incompatible genotypes. Aonla is mainly recognized for its high nutritive, medicinal and therapeutic properties. It contains high amount of vitamin-C (500-1500mg/100g), it is also rich in pectin, iron, calcium and phosphorus. Dried fruits of aonla can be used in curing haemorrhage, diarrhea, chronic dysentery, diabetes, jaundice, dyspepsia and cough. Recently, aonla gained more popularity in arid and semi- arid region of the country because of its hardy nature, prolific bearing capacity and ability to grow under various adversities as a remunerative crop (Shukla et al.2002). Aonla is the main ingredient of Chavanprash and Triphala powder, used for curing different   human ailments. Fruit contains a chemical substance gallic acid and leucoanthocyanin, having antioxidant property.

India produces all deciduous fruits including pome fruits (apple and pear) and stone fruits (peach, plum, apricot and cherry) in considerable quantity. These are mainly grown in the North-Western Indian States of Jammu and Kashmir (J&K), Himachal Pradesh (H.P.), Uttarakhand and in Uttar Pradesh. The North-Eastern Hills region, comprising of the States of Arunachal Pradesh, Nagaland, Meghalaya, Manipur and Sikkim also grow some of the deciduous fruits on a limited scale. The sub tropical region lies between 150 and 300 north of equator covering North Indian plains, the gangetic basin, large parts of North eastern state, western ghats, nilgiri regions etc. In this zone spring is generally frost free and chilling availability ranges from 50-500 hours. This region is not considered proper for temperate fruit growing but grows several low chilling varieties of peach, plum, pear etc. Deciduous fruits, such as peach and nectarine, require accumulated exposure to cool temperatures during winter dormancy for bud break and the resumption of normal growth the following spring. Minimum amount of accumulated cool temperature exposure needed for normal growth, which varies by cultivars, is referred to as the chilling requirement. Due to introduction and adaptation of low chilling cultivars of peach, plum and pear, they are also now being grown commercially in certain areas of the north Indian plains.

Apricot (Prunus armeniaca L) is the most important fruit crop of cold arid regions of India. It is one of the most delicious of temperate fruits having pleasing flavour and truly one of the most delectable of the stone fruits.  Exceptional fruit quality consists of blending of sugar and acidity and strong apricot aroma. It has been appreciated and grown for thousands of years on slopes of mountains in Asia and at least two thousand years in Europe.  There are many uses of apricot. It is enjoyed as fresh fruit but a large portion of the production worldwide is preserved primarily by drying. In China, apricot was not only dried but also preserved by salting and smoking. In Japan, apricot (mume) flowers are revered for their beauty and are used since 7–8th century for ornamental purposes.

Giant granadilla, Passiflora quadrangularis L. (syn. P. macrocarpa M.T. Mast.) is the largest fruit in the genus Passiflora. With more than 450 species, Passiflora is the most important genus of family Passifloraceae. It is further divided into 24 subgenera (Killip, 1938). Most of the species producing an edible fruit belong to subgenera Passiflora and Tacsonia. Many species have ornamental interest because of unique and spectacular flowers, or are used for their sedative, antispasmodic, antibacterial, and insect-resistant properties.

The Andaman and Nicobar group of Islands, popularly known as the Bay islands, consists of 572 islands, islets and rocks, situated off the Eastern coast of India. The Islands are covered from coast to coast with an almost impenetrable growth of luxuriant tropical rain forests. The luxuriant growth of dense forests with tangled mass of climbers, lianes, canes and plant communities provide an additional source of income. Many species of bamboos, bushes, shrubs and stunted trees have tremendous values (Mondal, et al 2000). Most of the diversity is still collected from wild forest habitats largely composed of trees, shrubs and other perennial vegetations. Underutilized fruits provide food, nutrition and sustenance to the natives. Broadly, such underutilized diversity in edible fruits falls into four categories (Groot et al 1993).

Genetic resources for food and agriculture are the biological basis of world food and nutrition security and they directly support the livelihood of people. Horticultural genetic resources are a few of biological assets available to resource-poor farmers to ensure sustainable production to improve livelihood options. Genetic diversity gives resource-poor farmers a low cost option to manage the shocks and vulnerability of production systems by its ability to adopt to changing environments. It is the foundation upon which plant breeding depends for the creation of new varieties and is, therefore, of critical public value for global food security. The rapid loss of genetic diversity (genetic erosion) is a worldwide concern and is particularly severe among crop landraces. Farmer’s varieties or landraces may contain co-adapted gene complexes that have evolved over decades and are the most valued genetic resources as they provide options for a range of climatic and edaphic stresses. Therefore, agricultural biodiversity has a critical public value for global food security (FAO, 1978).

Aonla or Indian Gooseberry (Emhlica officinalis Gaertn. syn. Phyllanthus embfica L.). belonging to family Euphorbiaceae. is an indigenous fruittree to Indian sub continent. It is one of the most important commercial crops suitable for marginal soils and various kinds of waste lands particularly salt affected lands. A lot of genetic variability is available in India with respect to growth and fruit quality characteristics of aonla. Almost all the budded varieties of aonla were selected from naturally occurring superior chance seedlings having in view their earliness, lateness, hardiness to adverse conditions, yield and superior fruit quality.

1-or successful aonla orchards, it is utmost necessary to have basic knowledge of various cultivars suitable for a particular set of environmental and soil conditions.

Plants yielding oilseeds are economically important in India next only to food crops and play an important role for sustainability of  cropping systems and soil health. Oilseeds scenario in the country underwent a sea change in  last fifteen years. India changed from net importer in  1980s to a net exporter  during  early 1990s. Again, it is back to net importer importing more than 40 % of its annual edible oil needs. Country’s demand for edible oils is  rising to double  the current level of 4% (as against productivity growth of 2% in 1986-2001) in  next 12 years (Hegde 2004). To meet  challenges of oilseeds production, there is  need to adopt multi-pronged strategy which involves enhancing production through area expansion and productivity improvement through improved technologies and value addition . As a progressive step in this direction of self sufficiency, there is  need to identify alternative oilseed trees/plants which can be grown in wastelands. There are more than 300 different kinds of tree species which bear seeds  rich in oil and  introduction of simarouba is an important step in this direction. National Oilseeds and Vegetable Oil Development (NOVOD) Board under Ministry of Agriculture  identified simarouba as a potential Tree Bearing Oilseed (TBO) for popularization in India and placed it in  first place in their list of importance.

Tamarind (Tamarindus indica) or Imli is also called  Indian Date. It is a large broad leaved, tropical tree found in India and many parts of Asia.  Tamarind is native to tropical Africa and grows wild throughout  Sudan. It was introduced to India so long ago that it is now reported as indigenous. Sometimes during  sixteenth century, it was introduced into America and today it is widely grown in Mexico.
 
There are large areas of marginal and waste lands, which are not suitable for cultivation of fruits like banana, citrus, sapota, litchi, mango, pomegranate etc., either due to poor quality of soil or lack of water resources. Such lands are suitable for  cultivation of underutilized fruit crops like tamarind which is not so popular among  farmers due to following reasons:

Karonda is an indigenous, under utilized fruit of India. It is a hardy multipurpose horticultural bush flourishing well without much care in arid and semi-arid areas. At present ,emphasis is being laid on protection and  production value of karonda plant. It is grown as hedge for beautification which  serves as one of the best bio-fencing materials because of  thorny  nature. It is also grown as an ornamental plant due to its beautiful cherry like fruits. Karonda plants are useful in many ways as detailed  below:
 
Fruit: Karonda fruit is a rich source of iron and contains a fair amount of vitamin C, and therefore very useful for curing of anaemia and has antiscorbutic properties. Enthomedically,  fruits are used as an astringent, antisorbutic and as a remedy for biliousness. Mature fruit contains high amount of pectin  and therefore, besides being used for making pickles and chutney, it can be exploited  for making jelly. Raw fruit can be used for making chatney.

Leaf: Karonda leaves are palatable and contain a fair amount of nutrient which are browsed by sheep, goats and camels in arid and semi arid areas.If fruits fall on ground, enrich soil by adding organic carbon and other mineral nutrients. It reduces evaporation  from  soil underneath due to dense foliage. Leaves  are used for feeding silk worm.  Leaf decoction is used against intermittent fever, diarrhoea, oral inflammation and ear ache.

Morinda citrifolia L is a unique horticultural plant belonging to Rubiaceae family. It has a tremendous demand because of its high medicinal value. Increase in demand has led to commercial farming of the tree. Noni is an ideal plant for mixed farming with other horticultural plantations. There is concurrent efforts to select early bearing plants with big size and fruits.  Noni can be grown in any type of soil under adverse climatic conditions.  Crop Improvement, nutritional requirement, water requirement, pest and disease management are the research priorities in Morinda citrifolia.

Indian Noni (Morinda citrifolia) is popularly known as Indian mulberry belongs to Rubiaceae family.  It is also called great Morinda, Cheese fruit, Mouse’s Pine Apple, Nono, Jumbie bread fruit, Hog apple. Noni was one of the most widely used medicinal plants in Polynesia prior to European contact, and continues popular among modern population. Noni is commonly known as canary wood in Australia, Kura in Fijii, mora de la India in spanish, nono in Tahiti and Nin in Marshall Island. Medicinal values of Noni were known to man many centuries ago. Uses of Noni were mentioned in Indian ethnopharmacology and ayurvedic medicines. Noni is grown as medicinal plant in most of  South Indian temples as sacred plant like basil (Tulasi). In India, it is called by several names in different  regional languages like nuna, manjanathi, manjanuna in Tamil,  molugu, mogal, bundamaddi in Telugu, kakaiplam, kattapitalavam, mannanatti in Malayalam, tagatemara, haladipavete in Kannada, Ach Al in Hindi, Paphan, Achchhulca in Sanskrit, Aseti, Nagkura, Mundari solidaru in Marathi.

Mango is the choicest fruit of tropical world. Originated in Indo-Malayan region (Mukherjee, 1985), more than one thousand varieties are under commercial cultivation in India (Mukherjee 1949). South Indian varieties of mango are distinct (Yadav and Singh, 1985).  Naik and Gangolly (1950)  described 135 South Indian varieties, taking fruit character as the main criteria. North Kerala experiencing humid tropical climate is an important zone of variability of mango (Kannan, 1982). Polyembryonic mango cultivars like ‘Vellaikolamban’, ‘Kurukkan’ and ‘Bappakkai’ are traditionally grown here. Over the years, there is erosion in  gene pool of rich varietal wealth due to deforestation, urbanisation and large scale rubber cultivation in Kerala. Establishment of field gene bank is an important ex situ conservation strategy. Systematic attempts to conserve  genepool  resulted  in collection of  more than 1266 varieties in various field gene banks in our country (Chadha, 1976). Field Gene Bank (FGB) has the advantage of being continuously evaluated and desired accessions can immediately be utilized directly or in breeding programmes. Field gene bank very often represents only a fraction of variability of the gene pool and  enrichment of the collection is always required for capturing  available diversity.

Spine gourd or teasle gourd (Momordica dioica : Roxb Syn.Momordica roxburghii G. Don, M. wallichi, M J Roem) is a rhizomatous, perennial and distinctly dioecious species of family Cucurbitaceae and  grows widely in many parts of India, mostly confined to  Eastern and South Eastern states. Vernacular names are kartoli,kakrol,meethakarela, padora, bhatt karela, palupagal, tumba, tumpai, golkandra, kankad, kankera, bara-karela, kankoda, kankodan, kantola and phalguni. In India it is mainly grown in Orissa, Bihar, and West Bengal .It is  found in nature in the Punjab, Uttar Pradesh, Rajasthan, Madhya Pradesh, Kerala and Maharashtra especially in areas with the least human interference. This is  a delicacy for its typical taste, attributed to high seed protein content. It also contains high amount of carotene (162 µg/100 g of edible portion) (Gopalan et al., 1982) and its tuberous roots have medicinal value too. It is a cheap source of vitamins and minerals (Bhuiya et al., 1977). This vegetable is gaining popularity  because of its high demand in  market. Certain limitations like lack of awareness among  farmers, non-availability of quality planting materials of standard varieties, unpredictable sex ratio in seedling progenies are arresting the expected spread of this nutritious vegetable (Ali et al., 1991).