11 Mar Hybrid Seed Production System in Wheat
गेहूं में संकर बीज उत्पादन प्रणाली Heterosis is the manifestation of heterozygosity expressed as increased vigour, size, fruitfulness and resistance to disease, insects or climatic extremes relative to either the high-parent or the mid-parent value. Varying estimates of heterosis have been reported in wheat for various traits of economic importance. It is generally known that hybrid advantage is a function of three factors: breeding-method efficiency (rate-of-progress); negative or positive effects of the system used to produce the hybrid; and the inherent level of heterosis. In wheat, one of the major constraints in hybrid development has been the lack of an effective and efficient seed production system. Here we discuss two different methods of seed production in wheat. 1. Cytoplasmic Male Sterility based system Wilson and Ross (1962) were the first to describe a workable cytoplasmic male sterile, nuclear-restoration system when they reported that Triticum timopheevii cytoplasm induces male sterility with largely neutral effects on agronomic and quality characteristics. This discovery led to the establishment of a number of research programmes to evaluate alternate cytoplasmic sources of male sterility with common wheat and the nuclear genes necessary to restore fertility to the F1 hybrid. Virmani and Edwards (1983), in a comprehensive review of cytoplasmic male sterility, reported that 15 different cytoplasms of the genera Triticum and Aegilops...