High land productivity is a must for any commercial cultivation including Hevea brasiliensis (rubber). Also, the high demand for natural rubber has placed great pressure on expanding rubber cultivation to new and non-traditional areas. Understanding the ecophysiological principles behind the measures of productivity improvements is vital for wide application of these measures and to assess their sustainability. This review discusses the ecophysiological principles and tools used, along with the measures taken, to address productivity needs in terms of: genotype selection, determination of optimum planting density, and establishment of intercropping systems. Breeding for high yields and selection of suitable genotypes for different growing conditions are a top priority throughout the research history of rubber, however, early selection tools are necessary to reduce the time required for this process. As for any crop, photosynthesis drives the productivity of the rubber crop and, therefore, factors that govern and/or parameters that indicate the efficiency of photosynthetic productivity under field conditions could be used as tools in the selection of Hevea genotypes. Particularly for the early selection of genotypes in breeding programmes, mature crop characteristics which determine crop photosynthesis and productivity, should be linked to juvenile plant characteristics. The spatial and temporal efficiency by which plants acquire growth resources determines the overall productivity of the rubber crop, hence the optimum planting density and suitable crop combinations in intercropping systems. Changes in crop microclimate influence the efficiency of resource capture and thereby can be important for determining planting density and intercrops. Research needs regarding all the above aspects are also discussed.
Rubber; Genotype selection; intercropping; planting density; physiology
