C) Development of plants tolerant to abiotic stress which can be grown on degraded lands

A) Use of micropropagation and mycorrhiza for reforestation

One of the approaches to tackle this problem is to develop strong and superior species which have the capability to grow well on degraded lands. This can be done by using mass multiplication which involves starting aseptic culture, multiplication of shoot using shoot apical meristems or buds, rooting of in vitro formed shoots, transfer, acclimatization and adaptation of micropropagated plantlets in the field. Using this methodology an estimated 500 million plants of diverse nature have been produced.

Mycorrhizae, which are symbiotic non-pathogenic associations between plant roots and fungi, improves the seedling survival and growth by enhancing uptake of nutrients and water. They also lengthen the root life and provide protection against the pathogens. A list of fungi which can efficiently form mycorrhizae has been prepared. These fungi can be used as inocula which are applied to roots of seedlings, to allow formation of mycorrhizae. The experimental infection of micropropagated plants during rooting increases their survival chances in the field, which is very important in case of plantations on degraded lands.

B) Improvement of soil infertility through the use of nitrogen fixing bacteria, Rhizobium in association with leguminous trees and Frankia in association with non leguminous species.

Biotechnological methods are being developed to help the non-leguminous plants to survive under adverse conditions such as low nutrient supply. There are about 160 species of angiosperms, which are known to form nitrogen fixing root nodules with the actinomycetes bacteria belonging to the genus Frankia which is being used for this purpose. Frankia helps in nitrogen fixation in non-leguminous plant species therefore it can be used for land reclamation through reforestation due to high biomass production

with out the need of expensive nitrogen fertilizers.

c) Development of plants tolerant to abiotic stress which can be grown on degraded lands

The techniques like tissue culture and genetic engineering are being used to develop plants-resistant to abiotic stresses e.g. salinity, acidity, aluminium toxicity etc. The cell lines which exhibit resistance to salt stress are selected and then used for plantation on degraded lands. E.g. Brassica spp., Citrus aurantium, Nicotiana tabacum etc. Research is going on to understand the molecular basis of salt tolerance and to isolate genes responsible for this attribute so that salt tolerant plants can be developed using genetic engineering. In vitro selection for tolerance to abiotic stress like aluminium toxicity has been successful in certain plant species e.g. tomato, rice, barley, rice and wheat.

^HTriticale" which is a man made synthetic crop has been found suitable for growing on acid soils, dry and sandy soils, on alkaline and calcareous soils and on mineral deficient and high boron soils especially in countries like Kenya, Ethiopia, Ecuador, Mexico, Brazil etc. In China, a number of new stress resistant varieties of rice, wheat and tobacco have been developed using anther culture.

Date: 2016-03-03; view: 947