Heterosis in pearl millet: a physiological assessment

摘要

Pearl millet is a C_4 species with a very high photosynthetic efficiency and dry matter production capability. The traditional landraces are often tall, have thick stems and are excessively leafy. The biomass production in these landraces even underthe prevailing low-resource farming systems is very high (6-12 t ha~(-1)), while the harvest index (HI) is often below 20 percnet compared to over 30 percent for the improved cultivars (Anand Kumar 1989). Improvement in HI is a major thrust in breedingfor higher grain yield. Following the discovery of a cytoplasmic-genic male sterility (cms) system in pearl millet (Burton 1958) grain hybrids with shorter plant height were developed in India. These had a HI of 40 percent and produced 8 t ha~(-1) of experimental grain yields in 85 days. Hybrid vigor in pearl millet is expressed phenotypically as the production of greater amounts of plant tissue, grain or derived products. Obviously then the hybrid forms exhibit more growth than their inbred parents. Since growth is the product of biochemical reactions, heterosis will be manifested either by increased rates of metabolic reactions or by a more efficiently organized metabolic system. Increased reaction rates are achieved by enhanced enzyme activity. Enhanced activity must result from the presence of more enzyme (Hageman et al. 1967).