Plant genetic resources have been defined as the genetic material of plants, which is of value as a resource for present and future generations of people. They describe the variability within plants that comes from human and natural selection over millennia. Their intrinsic value mainly concerns agricultural crops.
In the State of the World’s Plant Genetic Resources for Food and Agriculture
(1998) the FAO defined Plant Genetic Resources for Food and Agriculture (PGRFA) as the diversity of genetic material contained in traditional varieties and modern cultivars as well as crop wild relatives and other wild plant species that can be used now or in the future for food and agriculture.
DIFFERENT KIND OF PLANT GENETIC RESOURCES:
Different kinds of Plant genetic resources are present. List of those is under given–
✓ Land race
✓ Obsolete varieties
✓ Modern Cultivars
✓ Breeding lines (meant for breeding programmes)
✓ Special genetic stock
✓ Wild forms & wild relatives
✓ Germplasm
✓ Mutants
Brief discussion of these different kind of plant genetic resources are under given-
LAND RACES
Landraces are farmer-developed and maintained cultivars. They are developed over very long periods and have co-adapted gene complexes.
So, we can say that it is a domesticated, locally adapted, traditional variety of a species of animal or plant that has developed over time, through adaptation to its natural and cultural environment of agriculture and pastoralism, and due to isolation from other populations of the species.
Landraces may be used as starting material in mass selection or pure line breeding projects.
ADVANTAGES OF LANDRACES OVER MODERN CULTIVATED AGRICULTURE:
✓ Landrace tolerance to advert climatic condition.
✓ Landraces may provide new alleles for the improvement of commercially valuable traits.
✓ Landraces still present a unique source of specific traits for disease and pest resistance, nutritional quality and marginal environment tolerance.
✓ Landraces provide a medium to advertise information about the conservation and use of crop landraces.
DISADVANTAGES:
✓ Landraces are generally less productive than commercial cultivars.
OBSOLETE VARIETIES
Improved varieties of recent past are known as obsolete cultivars. These are the varieties which were popular earlier and now have been replaced by new varieties.
For example, varieties K68, K65 and Pb 591 were most popular traditional tall varieties before introduction of high yielding dwarf Mexican wheat varieties.
These varieties are well known for their attractive grain colour and chapati making quality. Now these varieties are no more cultivated.
MODERN CULTIVERS
The currently cultivated high yielding varieties or the plants which are selected for desirable characteristics that are maintained during propagation are known as modern cultivars.
These varieties have high yield potential and uniformity as compared to obsolete varieties and land races.
Modem cultivars constitute a major part of working collections and are extensively used as parents in the breeding programme.
BREEDING LINES
A group of identical pure-breeding diploid or polyploid organisms, distinguished from other individuals of the same species by some unique phenotype and genotype.
Wild forms of cultivated species are available in crop plants. Such plants have generally high degree of resistance to biotic and abiotic stress and are utilized in breeding programmes for genetic improvement of resistance to biotic and abiotic stress.
SPECIAL GENETIC STOCKS
Genetic stocks, broadly defined as plants or populations generated and/or selected for genetic studies, represent a unique and growing class of extremely valuable germplasm which, depending on crop, type of genetic stock and user community may represent genetic resources of either transient or long-lasting value.
Genetic stocks can be divided into three general groups:
✓ Cytological stocks (e.g., chromosome addition/substitution, aneuploids, amphiploids
✓ Mutants (e.g., induced/insertion mutants, tilling populations)
✓ Germplasm sets (e.g., mapping populations, parental lines, reference germplasm).
WILD FORMS AND WILD RELATIVES
A crop wild relative (CWR) is a wild plant closely related to a domesticated plant, whose geographic origins can be traced to regions known as Vavilov Centres (named for the pioneering botanist Nikolai Vavilov). It may be a wild ancestor of the domesticated plant, or another closely related taxon.
Crop wild relatives (CWR) include the pro-genitors and wild relatives having potential for crop improvement. These are important but scarcely exploited component of the gene pool, have been undeniably beneficial to modern agriculture, providing plant breeders with a broad pool of potentially useful genetic resources.
GERMPLASM
Germplasm is living tissue from which new plants can be grown. It can be a seed or another plant part – a leaf, a piece of stem, pollen or even just a few cells that can be turned into a whole plant.
Germplasm contains the information for a species’ genetic makeup, a valuable natural resource of plant diversity.
It can be wild+ cultivated or indigenous+ exotic varieties of the species.
MUTANTS
Mutation breeding is used when the desired character is not found in the genetic stocks of cultivated species and their wild relatives. Mutations do occur in nature as well as can be induced through the use of physical and chemical mutagens.
For example, mutant gene pool Dee-Geo-Woo-Gen in rice and Norin 10 in wheat proved to be valuable genetic resources in the development of high yielding and semi dwarf varieties in the respective crop species.