Plant Breeding Science and Practice in the Twentieth Century: Some Landmarks

Abstract

This paper attempts a brief analysis of the growth of the science of plant breeding and some of its landmarks. Advances in our understanding of evolutionary and population genetics have significantly influenced the theory and practice of plant breeding. Pure line selections among the domesticated land races of crop plants in the various eco-geographic regions and selections from crosses between elite lines yielded cultivars, which helped to increase agricultural production during the 20th century. Induced mutations, chromosome manipulations and distant hybridization involving wild species and genera, generated lot of interest but their direct contribution to improved cultivars has been limited. Transgenics to date have succeeded largely in incorporating relatively simply inherited traits. The breeding procedures have become more and more reductionist as compared to an integrated individual as the unit of selection under evolution. Among the landmarks in plant breeding are: pure line selections in land races and selections from elite crosses in almost all crops; inter-specific cultivars of sugarcane grown across continents which became feasible because of their vegetative propagation. Recent improvements for yield and fibre characters in G. arboreum cotton resistant to sucking pests and tolerant to boll worms has been a significant development; other significant developments include exploitation of wider germplasm sources including dwarfing genes as in rice, wheat and sorghum to develop semi-dwarf, high yielding varieties with marked changes in adaptability, input responses, leading to more productive cropping systems like that of rice-wheat; exploitation of heterosis employing male sterility and other systems in crops like maize, sorghum, pearl millet, cotton, sunflower and castor. The performance of hybrid sorghum, pearl millet, cotton and sunflower in rainfed agriculture has been a major contribution.