Molecular manipulation of source-sink interactions in crop plants.
Randhir Singh; Malhotra, S. P.;
Proceedings of the Indian National Science Academy. Part B, Reviews and Tracts - Biological Sciences Year: 1999 Vol: 65 Issue: 6 Pages: 351-376 Ref: 8 pp. of ref.
1999
บทคัดย่อ
The world will have to produce about 50% more food by 2025 to feed an estimated population of about 8 billion. Furthermore, this increased demand will have to be met from less land with less water, less labour and less use of chemicals. Moreover, a large number of biotic and abiotic stresses and unfavourable postharvest conditions particularly in Asian and African subcontinents take a serious toll of crop production. Therefore, crop varieties with higher yield potential and yield stability are needed to meet the goal of increasing crop productivity. In the last 60 years of plant breeding, the total plant dry weight harvested per hectare has not increased significantly. Rather, the increase in crop yield had been mainly due to the improvement in harvest index. Therefore, the best strategy to increase crop yield would be to design the architecture of the crop plants in such a way that source-sink interactions are maximized. The molecular approaches to increase crop yield have therefore, remained r
estricted either to increasing carbon export in the photosynthetic active organs or to optimizing carbon utilization in storage organs. The approaches exploited maximally included overexpression of endogenous or heterologous enzymes in tissues or subcellular compartments where they do not normally occur, and underexpression of endogenous enzymes using antisense technology. Both these approaches have been successfully employed in manipulating different components of source-sink interactions such as primary photosynthetic processes, synthesis of transitory starch in chloroplasts, export of carbon out of chloroplasts, synthesis of sucrose, export of sucrose (phloem loading), phloem unloading, hydrolysis of sucrose, transport of metabolites into plastids and synthesis of seed reserves. In each of these cases, transgenic plants have been produced where the effect of over- and/or under- expression of specific enzymes involved in these processes have been studied in relation to partitioning of photoassimilates for
better crop production. The present review covers the current knowledge in the area of molecular genetics of source-sink interactions in crop plants.