Biodiversity

Biodiversity, Genetic Diversity in Pyrus

Importance of Biodiversity

Ø  Biodiversity provides recreational, psychological, emotional and spiritual enjoyment to human being.

Ø  Genetic variation is indispensable for effective management and use of plant genetic resources.

Ø  Plant genetic resources of cultivated crop plants as well as wild relatives have significant values to mankind as they provide food, fuel, shelter and industrial products.

Ø  Plant breeders require genetic variation (genotypes) for plant improvement.

Ø  Genetic diversity in wild relatives is very important, as these contain genes resistant to biotic and abiotic stresses.

Ø  The genetic diversity is the key component of any agricultural production system.

Reason for loss of Biodiversity

There are many reasons for such depletion including

Ø  Logging and fuel wood gathering

Ø  Deforestation due to road laying, urbanization and industrialization

Ø  Cleaning area for crops

Ø  Natural disasters

Ø  Insect-pests and diseases

Ø  Introduction of new varieties as genetically uniform modern varieties are replacing the highly diverse local varieties and landraces in traditional agro-ecosystem

Ø  Primitive varieties are being discarded after termination of breeding projects

Reasons of genetic diversity in Pyrus

Pyrus germplasm have rich source of genetic variability, accumulated through:

Ø  Heterogeneity due to naturally seed based propagation

Ø  Diversity in environments

Ø  Mutations

Ø  Hybridization because of naturally occurring inter-specific hybrids

Threats to wild pear germplasm

Ø  Evidences exist that the germplasm resources of fruit plants are threatened to extinct. Such reductions have serious implication for food security in the long term.

Ø  Erosion of plant genetic resources especially of fruits results in their large scale depletion of variability.

Ø  The Red List of the International Union for the Conservation of Nature (IUCN) currently contains about 5 Pyrus taxa threatened in different countries (Sindelar, 2002)

1. Turkey (P. salicifolia),

2. Germany and the Czech Republic (wild populations of P. pyraster)

3. Hungary (P. magyarica)

4. Japan (P. calleryana)

5. Taiwan (P. kawakami)

Need and reasons of genetic diversity in this region

Ø  Like others deciduous and temperate fruit species, pear existing in mountainous region of Azad Jammu & Kashmir in cultivated, wild, naturalized, and indigenous forms need to be explored.

Ø  Pyrus species could be classified as Western species (P. communis) and Eastern Species (P. pyrifolia, P. ussuriensis, P. pashia). This region (Northern Pakistan and neighboring area) is situated at the border of the distribution area of these two groups. Since Pyrus species can easily cross, there may be many interspecific hybrids in this area as well as introgression may occur.

Ø  These might have been introduced in ancient times from the neighbouring countries like China, Iran, Afghanistan, Soviet Republic of Kazakhstan, Uzbekistan, Tajikistan and Jammu & Kashmir (Indian held) through silk route or introductions made by rulers, travellers, missionaries and others.

Ø  Such germplasm poses genetic basis for tolerance to extreme cold, heat, drought, diseases and pests required for genetic extension in pear breeding programmes.

Ø  This huge variability in Pyrus is unexplored. No detailed characterization on the basis of molecular level has yet been conducted.

Characterization of pear germplasm

—  Diversity in fruit species is assessed on the basis of:

—  1. Phenotypical/morphological traits,

—  2. Biochemical techniques based on:

—                  a) Isozyme patterns

—                  b) Protein profile like SDS-PAGE 

—  3. DNA based molecular techniques like

—                  a) RFLP

—                  b) AFLP

—                  c) RAPD

—                  d) SSR

—                  e) ISSR etc

Charcterization of pyrus germplasm through microsatellite (SSR) markers

Ø  Morphological and phenological characterization provide the basic data for further evaluation

Ø  Physiological and proteins based tools are used to estimate the genetic diversity in Pyrus species on limited scale.

Ø  Molecular markers are useful in practice for cultivar identification and characterization because they are not influenced by variable environmental conditions.

Ø  Now-a-days, microsatillites are increasingly being used for fingerprinting the collections of fruit species.

Ø  Microsatellites or SSR markers have been proved highly useful due to their reproducibility, codominance and polymorphism as well as their transferability among related species and genera