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Home , Genetic pollution

GENETIC RESOURCES AND IN FRUIT CROPS

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What is biodiversity?

Biological diversity - or biodiversity - is a term we use to describe the variety of life on Earth. It refers to the wide variety of ecosystems and living organisms: animals, plants, their habitats and their .

Biodiversity is the foundation of life on Earth. It is crucial for the functioning of ecosystems which provide us with products and services without which we couldn’t live. Oxygen, food, fresh water, fertile soil, medicines, shelter, protection from storms and floods, stable climate and recreation - all have their source in nature and healthy ecosystems. But biodiversity gives us much more than this. We depend on it for our security and health; it strongly affects our social relations and gives us freedom and choice.

The term biological diversity was used first by scientist and conservationist Raymond F. Dasmann in the 1968. A similar term in the United States is "natural heritage." It predates the others and is more accepted by the wider audience interested in conservation. Broader than biodiversity, it includes geology and landforms.

Geneticists define it as the diversity of genes and organisms. They study processes such as mutations, transfer, and genome dynamics that generate evolution

The terms biological diversity or biodiversity can have many interpretations. It is most commonly used to replace the more clearly defined and long established terms, species diversity and species richness. Biologists most often define biodiversity as the "totality of genes, species, and ecosystems of a region". An advantage of this definition is that it seems to describe most circumstances and presents a unified view of the traditional three levels at which biological variety has been identified:

• species diversity

• ecosystem diversity

• genetic diversity

In 2003 Professor Anthony Campbell at Cardiff University, UK and the Darwin Centre, Pembrokeshire, defined a fourth level: Molecular Diversity.

A 2007 study conducted by the National Science Foundation found that biodiversity and genetic diversity are codependent—that diversity among species requires diversity within a species, and vice versa. "If any one type is removed from the system, the cycle can break down, and the community becomes dominated by a single species." At present, the most threatened ecosystems are found in fresh water, according to the Millennium Ecosystem Assessment 2005, which was confirmed by the "Freshwater Animal Diversity Assessment"

Distribution of biodiversity

Biodiversity is not evenly distributed, rather it varies greatly across the globe as well as within regions. Among other factors, the diversity of all living things (biota) depends on temperature, precipitation, altitude, soils, geography and the presence of other species.

Hotspots

A biodiversity hotspot is a region with a high level of endemic species. Hotspots were first named in 1988 by Dr. Sabina Virk. Many hotspots have large nearby human populations. While hotspots are spread all over the world, the majority are forest areas and most are located in the tropics. Diversity consistently measures higher in the tropics and in other localized regions. Generally terrestrial biodiversity is up to 25 times greater than ocean biodiversity.

Human benefits

Biodiversity supports ecosystem services including air quality, climate (e.g., CO2 sequestration), water purification, pollination, and prevention of .

Non-material benefits include spiritual and aesthetic values, knowledge systems and the value of education.

Although about 80 percent of humans' food supply comes from just 20 kinds of plants,] humans use at least 40,000 species. Many people depend on these species for food, shelter, and clothing. Earth's surviving biodiversity provides resources for increasing the range of food and other products suitable for human use, although the present rate shrinks that potential.

Agricultural Biodiversity

Agricultural biodiversity is a broad term that includes all components of biological diversity of relevance to food and , and all components of biological diversity that constitute the agricultural ecosystems, also named agro-ecosystems: the variety and variability of animals, plants and micro-organisms, at the genetic, species and ecosystem levels, which are necessary to sustain key functions of the agro-ecosystem, its structure and processes. Agricultural biodiversity is the outcome of the interactions among genetic resources, the environment and the management systems and practices used by farmers. This is the result of both natural selection and human inventive developed over millennia.

Dimensions of agricultural biodiversity

The following dimensions of agricultural biodiversity can be identified:

1. Genetic resources for food and agriculture:

Plant genetic resources, including crops, wild plants harvested and managed for food, trees on farms, pasture and rangeland species,

Animal genetic resources, including domesticated animals, wild animals hunted for food, wild and farmed fish and other aquatic organisms,

Microbial and fungal genetic resources.

These constitute the main units of production in agriculture, and include cultivated and domesticated species, managed wild plants and animals, as well as wild relatives of cultivated and domesticated species.

2. Components of biodiversity that support ecosystem services upon which agriculture is based. These include a diverse range of organisms that contribute, at various scales to, inter alia, nutrient cycling, pest and disease regulation, pollination, and sediment regulation, maintenance of the hydrological cycle, erosion control, and climate regulation and carbon sequestration.

3. Abiotic factors, such as local climatic and chemical factors and the physical structure and functioning of ecosystems, which have a determining effect on agricultural biodiversity.

4. Socio-economic and cultural dimensions: Agricultural biodiversity is largely shaped and maintained by human activities and management practices, and a large number of people depend on agricultural biodiversity for sustainable livelihoods. These dimensions include traditional and local knowledge of agricultural biodiversity, cultural factors and participatory processes, as well as tourism associated with agricultural landscapes.

Plant genetic resources:

Plant genetic resources represent sum total of the diversity that come from wild species and primitive forms, accumulated through evolution and natural selection, plant introduction, migration and and also material developed artificial and breeding. In other words “ the sum total of all allelic sources influencing a wide range of characters constitute the plant genetic resources.” It is the genetic wealth that a crop has acquired over millions of years of its existence under natural conditions or human cultivation and thus provides the raw material for further improvement through natural or human interference.

Genetic resources are, according to the international convention for biodiversity, living material that includes genes of present and potential value for humans. Plant genetic resources includes all our agricultural crops and even some of their wild relatives because they too often have valuable traits.

Plant genetic resources are of great importance as they form the basic raw material to meet current and future needs of crop improvement programmes. A wider genetic base assumes priority in plant breeding research aimed at developing new varieties for increased crop production (Paroda, 1991). This diversity comprises of native land races, local collections, elite cultivars and wild relatives of crop plants.

All the aspects of plant genetic resources with direct relevance to their origin, current status, conservation and future use in plant breeding can be described as the following three interrelated activities:

• Origin and spread of crop plants

• Collection, evaluation and conservation plant genetic resources

• Utilization of germplasm for crop improvement

What is plant germplasm?

Plant germplasm is the living tissue from which new plants can be grown. Germplasm is usually seed, or it can be another plant part -- a stem, a leaf, or pollen, for example, or even just a few cells that can be cultured into a whole plant. Plant germplasm contains the genetic information for the plant’s hereditary makeup.

Centres of diversity/ centres of origin

Vavilove (1951), on the basis of geographic distribution of variation for various crops identified eight centres of origin of crop plants. Many of these area still remain rich source of variation. He further explained the pattern of distribution in two types of centres:

• Primary centre: Geographical region where a crop originated and had maximum diversity.

• Secondary centre: Regions of diversity formed due to migration of wild progenitors of some crops to other places from the centre of origin and were domesticated where these further developed into advanced and improved differential types through of genes from new types of wild and weedy plants. Regions of diversity: Following are the regions where maximum diversity is found in respect of different crop species.

Region Crops

Chinese-Japanese region Soybean, Citrus, Litchi, Bamboo, Rami, Tea

Indochinese-Indonesian Rice, Mango, Banana, Rambutan, Durian, Bread fruit, Bamboo, region Sago palm, Ginger, Coconut

Australian region Eucalyptus, Acacia, Macademia

Hindustani region Rice, Eggplant, Okra, cucumber, Banana, Mango

Central Asian region Onion, Radish, Carrot, Sesame

Near Eastern region Pear, Apple, Pea, Sesame

Mediterranean region Durum, olive, Radish

African region Durum, , kenaf, coffee

European Siberian Peach, Chicory region

South American region Potato, , Tomato, Groundnut, cassava, cacao, rubber

Central American and Maize, Chili, Cotton Mexican region

North American region Sunflower, plum, strawberry

Classification of plant genetic resources ❑ Cultivated species 1. Commercial varieties 2. or traditional local varieties 3. Breeding lines 4. Special genetic stocks ❑ wild species 1. For direct use 2. For Indirect use 3. Potentially utilizable

Wild relatives have been used as sources of disease, insect, and nematode resistance, to widen adaptation, to provide alternate cytoplasms and develop cytoplasmic sterility systems, to improve quality, alter modes of reproduction, induce short stature, increase crossability between species, improve resistance to stress, and increase yield. Some crops could not maintain commercial status without genetic support of their wild relatives.

Fig.1:Plant genetic resources

Biodiversity in fruit crops

Fruit species have higher adaptation to variable agro-ecological conditions and are suitable diverse agri-horticultural systems and fruit based cropping systems (Singh, 2003a)

The nature has provided innumerable plant species of which only about 5000 plant species are being used by human beings globally. Today only about 150 plant species are important in respect of food for mankind. There is greater dependence of very few plant species i.e. about 20-30 worldwide. This gradually, resulted in the loss of native genetic resources which are otherwise essential as building blocks of genetic diversity. It is estimated that there are about 500 species of tropical fruit trees under 30 families and 59 genera in Asia Pacific Oceana region (Arora, 1998). In Southeast Asia alone, there are 120 major fruit species and 275 minor fruit species (Verheij and Coronel ,1992). In Asia 50-60 species belong to the most important indigenous fruits (Arora and Rao , 1996). Citrus, banana, mango, jackfruit, litchi and durian occupy 80 per cent of total fruit production in the region.

India is an important centre of origin and diversity of many horticultural crops including fruit crops like mango, citrus and banana. The sub-continent has tropical, subtropical and temperate climate. Therefore, a variety of fruits originating in tropics, subtropics and temperate regions of the world have been introduced in India and many of them are commercially grown in the country.

Table 1.: The main centre of diversity for fruits in India

–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Region Species –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Western Himalayas Elaeagnus hortensis, Ficus palmata, Fragaria indica, Moms spp., Prunus acuminala, P. cerasiodes, P. cornuta, P. napaulensis, P. prostrata, P. tomentosa, Pyrus baccata, P. communis, P. kumaoni, P. pashia, Ribes graciale, R. nigrurn, Rubus ellipticus,R. moluccanus, H. rruticosuo, R. lasrocarpus, R. lanatus, R. niveus, R. reticulatus, Zizyphus vulgar/s.

Eastern Himalayas Fragaria indica, Morus spp., Myrica esculenta, Prunus acuminata, P. cerasiodes, P. jcirkinyii, P. nupauiensis, Pyrus pasn/a, Hives yraciale, Rubus lineatus, R. ellipticus, R. lasiocarpus, R. moluccanus, R. reticulatus North-eastern region Citrus assamensis, C. ichangensis, C. lndica, C. jambiri, C. la//pea, C. macroptera, C. media, C. aurantium, Docynia indica, D. hookeriana, Eriobotrya angustifolia, Mangifera sylvatica, Musa accuminata/M, balbisiana complex, M. manii, M. nagensium, M. sikkimensis, M. superba, M. velutina, Pyrus pyrifolia, P. pashia, Prunus cerasiodes, P. cornuta, P. jenkinsii, Ribes graciale, Rubus ellipticus, R. moluccanus, R. reticulates, R. lasiocarpus, Myrica esculenta.

Gangetic plains Aegle marmelos, Cordia myxa, C. rothii, Emblica officinalis, Grewia as/at/ca, Morus spp.; Phoenix spp.; Syzygium spp.; Zizyphus nummularia and other spp.; and Manilkara hexandra (more in North-Western plains).

Indus plains Meagre occurrence of Syzygium, rich variaton in Carissa bcongesta.

Western peninsular Artocarpus heterophyllus, A. lakooCha, Garcinia indica, Diospyros spp., Ensete superba, Mangifera indica, Mimosops elengii, Spondias pinnata, Vitis spp., Zizyphus oenoplia, Z. rugosa. Ruhus ellipticus. R. laeiocarpus. R. mo/uccanus.

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Temperate fruits genetic resources

Temperate fruit diversity in India extends from north (Jammu & Kashmir) to subtropical plains in the north, and also to Arunachal Pradesh in the east. Genetic diversity is rich in the north-western Himalayas and to relatively low extent in the north-eastern region. The important genera that constitute temperate fruits are Malus, Prunus, Pyrus, Juglans, Caryo, Corylus, Sorbus, Fragaria, Actinidia, Rubus, Ribes, Crataegus, Cydonia, Docynia, Hippophae, Diospyros and Cotoneaster.

Fruit Diversity in Asia

Asia is characterized by rich fruit diversity and about 500 species are distributed in its diverse ecosystems. Thus, a wide range of natural diversity occurs, well adapted to sub-humid, humid tropical and semi-arid conditions. In addition to the native fruit species that have been domesticated and diversified in this region, a large number of species of tropical American origin introduced in the distant past have developed agro- ecological niches and are well acclimatized (Verheij and Coronel, 1991; Arora and Ramanatha Rao, 1995). Over 70 cultivated species of major and minor fruits are presently grown in the region, along with some of the promising exotic tropical fruits (Arora and Ramanatha Rao, 1995). However, only about 20 species are better known under cultivation and these include banana, citrus, mango, pineapple, , durian, rambutan, jackfruit, litchi, longan, tamarind, chempedak, carambola, langsat, guava, sour sop, custard apple, salak, passion fruit and jujube (Verheij and Coronel, 1991; Singh, 1993; Arora and Ramanatha Rao, 1995), the predominant fruits being banana, pineapple, citrus, mango and papaya.

In the humid tropics which hold very rich species diversity, tropical fruit trees(TFT) are a major component of multi-crop farming systems including home gardens. Some of these species have been well adapted to marginal lands, and in and farm-forestry systems (Verheij and Coronel, 1991).

An example of rich fruit diversity in Asia is the genus Mangifera which comprises 58 species (Kostermans and Bompard, 1993) and is naturally distributed in south, southeast and east Asia. The Malay Peninsula, the Indonesian archiplego, Thailand, Indo- China and the Philippines are the seats of diversity for Mangifera species (Mukherji, 1985; Bompard, 1988; Kostermans and Bompard, 1993). About 26 species have edible fruits, either eaten as fresh fruits or used to prepare jams, jellies or preserves, the most important of which is mango (Mangifera indica).The other important species, which produce edible fruits, are M. caesia Jack, M. foetida Lour, M. kemanga Bl., M. laurina Bl., M. odorata Griff. Lour. (Bompard 1992; Tanaka, 2 1976), M. pajang Kostermans (Bompard,1992) and M. sylvatica Roxb. (Tanaka, 1976) which, with the exception of the later, are mostly distributed in Malaysia and Indonesia. Besides mango, the other Mangifera species reported from India include M. andmanica, M. khasiana and M. sylvatica and M. camptosperma (Mukherji, 1985). A large array of cultivated and wild types occur in India. Seedling races derived from monoembryonic mango stones are the most important components of diversity available in India. Almost all commercial cultivars of mango have arisen as a result of seedling selection. Although most other countries in APO have 2-10 commercial cultivated mango varieties, India has around 1000 distinct varieties and about 30 of them are commercially grown.

Another good example is of Citrus. The genus Citrus occurs naturally from Northeastern India and Southern China to Northern Australia and New Caledonia. The cultivated species are native to the tropical and subtropical regions of Southeast Asia. The commonly grown citrus fruits belong to three genera, Citrus, Fortunella and Poncirus. All these genera are closely related, have intergeneric fertility and readily hybridize resulting in the development of several unusual plant forms with different names. There is a great amount of variation among Citrus species and cultivars as a result of frequent bud mutation, interspecific and intergeneric hybridization, apomixis and long history of cultivation (Shahsavar et al. 2007). The existence of intergeneric hybrids is common among these three genera (Nito, 2003). There are five citrus groups that are commercially important and these include sweet orange, mandarin (including Satsuma), grapefruit, lemon and lime and numerous varieties and cultivars exist. Kumquat (Fortunella spp.) is grown to a limited extent for fresh fruit and processing. Pummelos are of economic importance in many areas within Southeast Asia and China.

Rambutan (Nephilium lappaceum) is the most important species in the genus Nephilium. Three different forms of rambutan, (var. lappaceum, var. pallen and var. xanthioides) are recognized based on leaflet characteristics. Rambutan occurs from southern China through Indo-China region, Malaysia, Indonesia and the Philippines. All cultivars of rambutan have been produced by superior trees found in natural habitats. Jackfruit (Artocarpus heterophyllus) is a major fruit in south and Southeast Asia. It is usually classified in two major types based on the quality of its edible pulp. Many cultivars exist within both of these types and all the currently used cultivars are direct selections of desirable trees found in natural habitats. Similarly, durian (Durio zibethinus) and litchi (Litchi chinensis) are also important priority fruits in South and Southeast Asia and considerable diversity occur in these fruit species.

Table 2.: Occurrence of Species in Different Genera –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Fruits (Genera) Fruit Genera/Species –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Pome fruits (Malus Malus pumila, M. baccata, M. sikkimensis, M. dirangensis, and Pyrus) Pyrus jaqumontiana, P. polycarpa, P pyrifolia, P. pashia,

P communis

Stone fruits (Prunus) Prunus domestica, P. salicina, P. cerasifera, P. armenicana, Prunus nepaulensis, P dulcis, P. persica, P.prostrata, P. wallichii, P. cornuta, P. cerasoides, P. rnira

Nut fruits Juglans regia, J. nigra, Carya illinoesis, Cory/us avellena, C. colourna, C. ferox

Soft fruits Actinidia deliciosa, A. purpurea, A.arguta, Vitis himalayana, Rubus elipticus, R. nivus, R. biflorus, R. fruitcosus, R.lasiocarpus, Ribes nigrus, R. rubrum, R. furrnosanium, H.roezli, R. wolfi, R. aureum, R. triste,. R. burejens, R. petraeurn

Minor fruits Sorbus lanata, Crategus crenutata, C. oxycantha, Feijoe sellowiana, Cydonia oblonga, Diospyrus kaki, Docyinia hookeriana, D. indica, Pun/ca granatum, Vibernum contifollurn, V. lanata, Cornus capitata, Elaegnus umbellate, Castenia sativa, Dlea europaea Zizyphus jujube, Aesandra butracea. Pistachio Pinus girardiana, Hippophae rharnanoides. Ficus species

Wild fruits Aegle marmelos, Cordioblique, Emblica officinalis. Ficus pa/ma/a, Ficus roburghii, Myrica nagi, Opuntia dillenii, Ficus indica, Grewia subinaequalis, Passiflora edulis, Sorbus lonata, Rubus niveus, Fragaria nub/cola, Rubus ellipticus, Vitis lanata. Sorbushiu spidata, Zizyphus jujube, Spondias, Mangifera. Buchanania latifolia, Corylus colourna, Ribes rubrum, Hippophae salicifolia, H. rhamnoides and Cotoneaster baccillaris.

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Conservation of plant genetic resource

Why Conserve plant genetic resources/biodiversity?

The objective is to conserve sufficient diversity within each species to ensure that its genetic potential will be fully available for breeding work

Only a few crops are used in modern agriculture and these often have a narrow genetic base. This contrasts with the large number of land races with a substantial genetic variation used by earlier generations. If we do not counteract the increasing genetic impoverishment it may have serious consequences, especially when facing a changed climate.

Genetic variation is irretrievable

It has been shown that crop varieties with a narrow genetic base can be completely destroyed by diseases. The plant breeders must then go back to older varieties or closely related wild species in order to find resistance genes for the disease in question. Not even advanced gene technology can replace natural variation, with its abundance of genes and gene interactions. Gene interaction is irreplaceable and without it no breeding can take place.

To preserve is our responsibility

Organized preservation of genetic resources is a prerequisite for future generations to be able to breed crop varieties and face new challenges. We do not as yet know everything about future demands for crop varieties, but we do know that they will have to be part of a more environmentally friendly cultivation system, be of better quality and have improved resistances, especially when it comes to meeting the challange of we currently face. Conservation system

1. In Situ

2. Ex Situ

These two system should be considered complementary, not antagonisticIn situ conservation

✓ It consists in the legal protection of the area and habitat in which the species grows

✓ This is the preferred technique for wild plant

✓ The advantage is the evolutionary dynamics of the species are maintained

✓ The drawback is the cost, and the social and political difficulties which occasionally arise

Ex situ conservation

✓ It implies the collection of representative samples of the genetic variability of a population/cultivar, and their maintenance in germ-plasm banks or botanical gardens as seeds, shoots, in vitro culture, plants

✓ It is mainly used for cultivated plants multiplied by seeds

✓ Loss of genetic diversity

✓ Rapid environmental changes typically cause mass . One estimate is that less than 1% of the species that have existed on Earth are extant.

✓ The period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity. Named the , the reduction is caused primarily by human impacts, particularly . Conversely, biodiversity impacts human health in a number of ways, both positively and negatively.

✓ In 2006 many species were formally classified as rare or endangered or threatened; moreover, scientists have estimated that millions more species are at risk which have not been formally recognized. About 40 per cent of the 40,177 species assessed using the IUCN Red List criteria are now listed as threatened with extinction.

✓ The current and projected rate of constitutes the sixth major in the history of life on Earth – the first to be driven specifically by the impacts of human activities…….humans have increased the rate of species extinction by 100-1,000 times the background rates that were typical over Earth’s history

Fig,2: Conservation and utilization of biodiversity

Causes of Biodiversity Loss The immediate drivers of the decline in biodiversity are habitat loss, invasive alien species, over-exploitation of natural resources and pollution. Humanity is to blame for each of these. The main culprit is the destruction of natural habitat to accommodate arable and livestock farming, , urbanisation and industrial development.

The introduction of alien species has caused untold damage to native plants and animals.

Genetic pollution

Endemic species can be threatened with extinction through the process of genetic pollution, i.e. uncontrolled hybridization, introgression and genetic swamping. Genetic pollution leads to homogenization or replacement of local genomes as a result of either a numerical and/or advantage of an . Hybridization and introgression are side-effects of introduction and invasion. These phenomena can be especially detrimental to rare species that come into contact with more abundant ones. The abundant species can interbreed with the rare species, swamping its . This problem is not always apparent from morphological (outward appearance) observations alone. Some degree of is normal adaptation, and not all gene and genotype constellations can be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.

Species loss rates

During the last century, decreases in biodiversity have been increasingly observed. In 2007, German Federal Environment Minister Sigmar Gabriel cited estimates that up to 30% of all species will be extinct by 2050. Of these, about one eighth of known plant species are threatened with extinction. Estimates reach as high as 140,000 species per year (based on Species-area theory). This figure indicates unsustainable ecological practices, because few species emerge each year. Almost all scientists acknowledge that the rate of species loss is greater now than at any time in human history, with extinctions occurring at rates hundreds of times higher than background extinction rates. As of 2012, some studies suggest that 25% of all species could be extinct in 20 years.