Plant parasites that are carried in the soil and are immobile. They are usually dormant until a suitable plant root grows close to them. They include fungi, nematodes, bacteria, and insects. rotation is the most common method of controlling soil-borne parasites, but they should be taken into account when breeding for comprehensive horizontal resistance to all locally important parasites. Solanaceae
Except for the eggplant, which originated in India, all these crops are of a New World origin. Solanum melongena
Eggplant, also known as aubergine or brinjal, originated in India and is the only important Old World cultivated species of the family Solanaceae. The crop is cultivated for its fruit which is eaten as a vegetable. It is open-pollinated and hybrid varieties are useful. Quite an easy crop for amateur breeders . Solanum tuberosum
The potato, which originated in the equatorial highlands of South America. The potato of commerce is a tetraploid that is self-compatible but somewhat intolerant of inbreeding. In addition, there are a number of both wild and cultivated diploid species that are self-incompatible and allogamous . The original imports to Europe involved short-day potatoes in which tuber initiation was delayed until the autumn equinox in late September. This meant that the crop was likely to be destroyed by frost before it was mature. During the eighteenth century, day-neutral potatoes were developed in Europe, partly by deliberate breeding, and partly by natural selection. Unfortunately, nearly all development work during the past century has involved disease-free certification of seed tubers of very susceptible cultivars, as well as breeding under conditions favouring the vertifolia effect. As a result, modern potato cultivars have very low levels of horizontal resistance to very many pests and diseases, and this crop is one of the most heavily treated with crop protection chemicals. This problem has been greatly aggravated by the second mating type of Phytophthora infestans.
This is an excellent crop for amateur breeders working with horizontal resistance, particularly as even small increases in the levels of quantitative resistance will greatly assist organic farmers. There is a more detailed account in Return to Resistance, available as a sharebook at this website (<sharebooks.ca>).
See also: Neo-tuberosum, Sweet potato. Sorghum
See: Sorghum bicolor. Sorghum bicolor
Sorghum, also known as: milo, kafir, durra, feterita, kaoliang, mtata, sorgo, jola, jawa, guinea corn, and cholam. It is grown mainly in Africa, India, China, and USA.
Sorghum is the fourth most important cereal in the world, after wheat, rice, and maize. It is very drought-resistant and this makes it an important food crop in arid and semi-arid areas. Grain sorghums, as their name implies, are grown for grain which is used either for food or brewing. Sorgos and sweet sorghums are used mainly as fodder and for syrup production. Broom corn is used for making brooms. Relatively new dwarf hybrids allow harvesting by combine, and they have led to an increased cultivation of sorghum.
Sorghum is an open-pollinated, short-day plant. Hybrid varieties have been produced in USA. It is an excellent crop for plant breeding clubs that are located in an appropriate area.
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