Wild taxa are invaluable sources of resistance to diseases, insects/ pests, nematodes, temperature extremes, salinity and alkalinity stresses, and also of nutritional quality; adaptation; genetic diversity and new species. Utilization of wild relatives of a crop depends largely upon its crossability relations with cultivated varieties. Sev eral wild species are not crossable with the commercial cultivars due to various isolation barriers. Furthermore, in a few cases, hybridiza tion is possible only in one direction and reciprocal crosses are not successful, thus depriving the utilization of desired cytoplasm of many species. However, techniques have been developed to over come many barriers and hybrid plants are produced. New crop species have been developed by overcoming the F 1 sterility and producing amphidiploids and such crops are commercially being grown in the field. The segregation pattern ofF 1 hybrids produced by distant hybridization in segregating generations are different from the intervarietal hybrids. In former cases, generally, unidirectional segregation takes place in early generations and accordingly, selec tion procedures are adopted. In most of the cases, backcross or modified backcross methods have been followed to utilize wild species, and thus numerous types of resistance and other economical attributes have been transferred in the recurrent parents. Protoplast fusion has been amply demonstrated in a number of cases where sexual hybridization was not possible and, as a result, hybrids have been produced."

The esculent Lycopersicon esculentum, long thought to be poisonous, has become a major U. S. food crop and source of vitamins and minerals, thanks largely to genetic modification and new production technology Rick (1978) Tomato (Lycopersicon esculentum Mill. ) is one of the most important solana ceous vegetable crops grown worldwide under outdoor and indoor conditions. It has become an important commercial crop so far as the area, production, industrial values and its contribution to human nutrition is concerned. During the past few decades tremendous developments have contributed to the knowledge and understanding of various areas of genetics, breeding and biotechnology and voluminous literature has been generated. The purpose of preparing this monograph is to give a comprehensive up-to-date treatment to the various aspects of genetic improvement of tomato. The emphasis has been placed on cytology, classical and molecular genetics, reproductive biology, germplasm resources, hybrid seed production, use of wild taxa, selection/ breeding methods, breeding for abiotic and biotic stresses, processing and quality breeding, improvement for mechanical harvesting, and biotechnology: tissue culture, protoplast fusion, and genetic transformation. These topics are presented in 22 different chapters. However, a few aspects have been discussed in more than one chapter. For example, seed production is treated in chapters 1, 4 and 8; molecular biology/genetic engineering in chapters 3 and 22 and heterosis in chapters 8 and 16."