Pre-breeding and Participatory breeding
An integrated pre-breeding procedure leading to the production of novel genetic combinations and designer genotypes, and participatory breeding involving the development of location specific varieties jointly with farming families, would help to combine genetic efficiency and diversity in a mutually reinforcing manner. This will help to avoid the danger inherent in spreading single genotypes over large areas. Also, sustainable agriculture needs for its sustenance location-specific varieties.
At MSSRF, a group of scientists headed by Dr Ajay Parida have been working during the past 8 years on the transfer of salinity tolerance genes from mangrove tree species to annual crops. This program was initiated with support from the Department of Biotechnology, Government of India, to prepare genetic material which will prove to be useful if sea levels rise, thereby safeguarding coastal agriculture.
One such gene, Betaine Aldehyde Dehydrogenase (BADH) cloned from a highly salt tolerant mangrove species, Avicennia marina is currently being evaluated in transgenic tobacco and Brassica systems for its efficacy. BADH converts betaine aldehyde to glycine betaine. Glycine betaine is an effective compatible solute and its accumulation confers salinity tolerance in plants. The transgenic tobacco and Brassica, over-expressing the BADH from Avicennia, conferred salinity tolerance up to 250 mM NaCl. The work on isolation of a gene that can convert the ubiquitous choline into betaine aldehyde is being actively pursued. Other genes relating to stress resistance isolated and characterized from the mangrove species include Catalase (CAT), Superoxide Dismutase (SOD), Glyoxalase and Sodium Hydrogen Antiporter. These genes are being evaluated for their expression in transgenic systems. Also, transformation work is in progress in rice and Vigna(Ajay Parida, Personal communication).
Once transgenic plants with the desired salinity tolerance are developed, they will be used, after obtaining the necessary clearance from the regulatory authority, in breeding programs undertaken jointly with farm families. The aim will be to transfer to numerous locally adopted varieties the salinity tolerance character in coastal as well as in inland areas where salinity is a problem.
Bio-remediation: Sequestration of salt
Salinity is responsible for major crop losses, particularly in semi-arid and irrigated agriculture. High salinity in soil may result from excessive irrigation or the excessive application of chemical fertilizer. Usually sulfates, chlorides and bicarbonates of Na+, Mg2+, and Ca2+ contribute to the salinity of soil. Sodium (Na+) is the predominant soluble cation in most saline soil water, particularly in coastal areas. An alternate approach, for practicing crop cultivation in saline environments, is the amelioration of soil salinity in agricultural habitats. Conventionally, it is done by addition of gypsum followed by leaching out of excess salts by flooding. A biological approach to solving this problem will be preferable. Anabaena torulosa, a blue green alga was found to grow and enrich the nitrogen status of moderately saline "Kharland" soils. A. torulosa was found not to intracellularly accumulate Na+ but entrap the cation in its extracellular mucopolysaccharides sheath, thereby reducing the availability of this deleterious cation to the crops. Research on the biological sequestration of salt from the soil may be rewarding.
Under a collaborative research program between the Bhabha Atomic Research Centre and MSSRF, a salt tolerant culture of A. torulosa, along with AL31 were given for testing in the southern coastal region. Several field trials have been conducted so far. The trials have shown that A. torulosa established very well along with local Ananaena sp in the field condition. Enhanced nitrogenase activity was observed in the field after transplantation. Up to 64% salt sequestration was observed when 1000 ml of innoculum was added (Sudha Nair, Personal Communication).