Breeding of Fruit and Plantation Crops

Tissue culture

Cashew :

• Production of somatic embryogenesis and plantlet regeneration which could subsequently be useful for genetic transformation to introduce genes for resistance to tea mosquito and stem and root borers, micro grafting techniques, developing haploids and isogenic lines and molecular characterization of existing genetic diversity.

Coconut:

• Embryo culture has become an important tool for safe germplasm movement. The 3 components of an embryo culture protocol are field collection of embryos, in-vitro conservation and retrieval, and ex-vitro establishment of seedling. Success achieved in the routine use of embryo culture for field collection and short-term storage up to 2 months in sterile distilled water and nearly 80 % of the embryos could be retrieved. A medium containing 2g/litre of activated charcoal without sucrose could store the embryos for 6 months which gives 77% germination.

Cryopreservation of coconut germplasm:

• Use of in-vitro culture techniques including slow growth and cryopreservation, represents an important additional option for safe medium and long term conservation of coconut germplasm. Immature embryos from nuts of 7-8 months after pollination could be successfully cryopreserved and retrieved. The embryos are dessicated for 4 hours in air current of laminar flow cabinet, pretreated for 11 -20 hours on a medium containing 600g/lit sucrose and 15% glycerol and then rapidly immersed in liquid nitrogen. Whole plants could be produced from 73.93 % of cryopreserved embryos.

Coffee :

• The major constraints of coffee production where tissue culture techniques can offer solutions are development of resistance through genetic engineering for fungal diseases particularly leaf rust, introduction of Bt gene to control of berry and stem borers, use of embryo rescue for interspecific crosses from resistant species and development of tools for quality improvement for uniform maturity, short maturation cycles, high soluble solids, large bean size and density, better aroma and less caffeine content. Synthetic seed technology for encapsulating embryos in sodium alginate has been developed. Anther culture technique has been successfully employed for callus induction and plantlet regeneration in interspecific hybrid between C. congensis x C. canephora. Plants are successfully regenerated from the embryo cultures of 3 interspecific crosses involving C. canephora as one of the parents and 3 indigenous wild species viz., C. bengalensis, C. travencorensis and C. wightiana.

Oil palm:

• The technique of cryopreservation in oil palm has been standardized and the embryoids could be stored for 15 months in liquid nitrogen and then plantlets can be regenerated from frozen embryoids.

Rubber:

• Isogenic lines evolved from anther culture could be used in heterosis breeding. Gene transformation protocols, through Agrobacterium and by using gene gun have been perfected and further success in this line will lead to improvement of rubber through biotechnological tools.

Tea:

• The major areas where biotechnology would be useful in tea improvement are micropropagation for mass multiplication of elite tea clones, application of molecular markers for characterizing tea clones as well as quality, genetic engineering for developing resistance to blister blight and identification , characterization and gene transfer for low- caffeine tea. Tissue culture-derived clones are more vigorous than conventionally propagated plants through vegetative methods and produced higher number of laterals in response to centering and tipping.

Cocoa
Somatic embryogenesis

• From floral parts genetically identical embryos are formed. These embryos grow and forms seedling like architecture, which is advantageous, reduces pruning (Penn State University, USA). Secondary embryogenesis, single embryos can form multiple secondary embryos each identical to the first.MS (Murashige and Skoog) + NAA 1.8 + Thiamine 1mgl-1+ CW (Coconut water) 15% + Sucrose 4% (KAU media for somatic embryogenesis).MS basal medium supplemented with 0.5 mg/l of NAA and 0.5 mg/l of BAP is found to be best with leaf explants for optimal callus production (CPCRI)

Cryopreservation of cocoa

• Shoot tip is carried out by three methods viz.,Encapsulation- dehydration, pregrowth- desiccation and Droplet-freezing method. For preculture, McCown’s Woody Plant Medium (WPM) supplemented with sucrose 0.75M and ascorbic acid 0.1g/litre, and for retrieval, WPM medium with 0.6M sucrose and BAP(1mg/L), GA3 (0.5mg/L) and NAA(0.2mg/L) are used. In pre growth desiccation method shoot tips were incubated in 1.5M sucrose solution for 24 hours that showed slight enlargement of tissues in both cryopreserved (+LN) and non-cryopreserved (-LN) shoot tips. There is no cell wall breakage or cell shrinkage. The cell viability was tested by using 0.1%TTC (2, 3, 5 triphenyl tetrazolium chloride) solution. TTC test gave positive result (red colour) only for cryopreserved shoot tips following pregrowth- desiccation that resulted in 5% initial survival.