Initiation of somatic embryogenesis in white spruce (Picea glauca): genetic control,culture treatment effects,and implications for tree breeding

The degree of genetic control and the effects of cultural treatments on somatic embryogenesis (SE) in white spruce were investigated with material derived from six-parent diallel crosses, including reciprocals. Thirty zygotic embryos from both immature and mature cones of each family were cultured in media with either 2,4-D or Picloram immediately after the collection of cones and after 2 months of cold storage. There were significant differences in SE initiation between immature and mature explants, and fresh and cold-stored seeds, but there was no significant differences with culture media effect. Significant variances due to families and to family x treatment interactions were found. The mean percentage of explants that initiated SE in each family ranged from 3.3% to 54.6%, with an overall average of 30.5%. The partitioning of family variance revealed that 21.7% was due to general combining ability effects, 3.5% was due to maternal effects, and 5.5% was due to reciprocal effects, but that the specific combining ability (SCA) was negligible. Variance due to interactions of family x treatments collectively accounted for 32.6%, while the remaining 37.8% of variation was accounted for by random error. However, when comparing the responses obtained with the treatment combinations, the SE response for freshly excised immature embryo explants showed comparatively large SCA variance, whereas the SCA variance was very small in the other treatment combinations.     

Biotechnological advances in mango (Mangifera indica L.) and their future implication in crop improvement: a review

Biotechnology can complement conventional breeding and expedite the mango improvement programmes. Studies involving in vitro culture and selection, micropropagation, embryo rescue, genetic transformation, marker-assisted characterization and DNA fingerprinting, etc. are underway at different centers worldwide. In vitro culture and somatic embryogenesis of several different genotypes have been achieved. The nucellus excised from immature fruitlets is the appropriate explant for induction of embryogenic cultures. High frequency somatic embryogenesis has been achieved in some genotypes; however, some abnormalities can occur during somatic embryo germination. Embryo rescue from young and dropped fruitlets can improve the hybridization success in a limited flowering season. Protocols for protoplast culture and regeneration have also been developed. In vitro selections for antibiotic tolerance and fungal toxin resistance have been very promising for germplasm screening. Genetic transformation using Agrobacterium tumefaciens has been reported. Genes that are involved with fruit ripening have been cloned and there have been attempts to deliver these genes into plants. DNA fingerprinting and studies on genetic diversity of mango cultivars and Mangifera species are also being conducted at several research stations. The purpose of this review is to focus upon contemporary information on biotechnological advances made in mango. It also describes some ways of overcoming the problems encountered during in vitro propagation of mango.     

Progress in tissue culture,genetic transformation and applications of biotechnology to trees: an overview

Trees are an integral part of human life, and a vital component of biodiversity. Forest trees in particular are renewable sources of food, fodder, fuel wood, timber and other valuable non-timber products. Due to the rapid growth of population and the human desire to progress, there has been a tremendous reduction in forest cover from the earths surface. To maintain and sustain forest vegetation, conventional approaches have been exploited in the past for propagation and improvement. However, such efforts are confronted with several inherent bottlenecks. Biotechnological interventions for in vitro regeneration, mass micropropagation and gene transfer methods in forest tree species have been practised with success, especially in the last decade. Against the background of the limitations of long juvenile phases and life span, development of plant regeneration protocols and genetic engineering of tree species are gaining importance. Genetic engineering assumes additional significance, because of the possibility of introducing a desired gene in a single step for precision breeding of forest trees. There are no comprehensive and detailed reviews available combining research developments with major emphases on tissue culture and basic genetic transformation in tree species. The present communication attempts to overview the progress in tissue culture, genetic transformation and biotechnological applications in the last decade and future implications.