The fungus which causes 'witches' broom' disease of cocoa. Crocus sativa
Saffron. A much prized spice and yellow colouring obtained from the stigmas of this Crocus. Saffron is the basis of French bouillabaisse, Spanish paella, English saffron buns, Jewish gilderne, Russian challah, Indian zaffrani chawal, and Persian sholezard. Saffron is also the most expensive spice of them all, because the anthers of a crocus flower are the most labour-intensive of all crops to harvest.
The wild progenitors of the saffron crocus are extinct, and this is an indication of its antiquity. Like garlic, the cultivated crocus does not set seed, and, it can be propagated only by corms. Multiplication of the crop is a very slow process because only two or three new corms are formed each year at the base of the old corm. It is not known how many clones exist but it is quite clear that all of them are ancient, and that they have been cultivated for millennia without any use of crop protection chemicals. Not recommended for amateur breeders . Cronartium ribicola
White pine blister rust. This is a heteroecious rust of five-needled pines (Pinus spp.), and its summer host is Ribes spp. It was apparently introduced to North America at the turn of the nineteenth century, where it largely destroyed the white pine forests. It is thought (but not proved) that this introduction was an allopatric pathotype native to Eurasia, and that a local, North American pathotype had been present all the time. The two pathotypes would have become isolated from each other some sixty five million years ago with the separation of the continents. This would explain why an apparently functioning gene-for-gene relationship exists in the North American pathosystem of the Eurasian pathotype. Apparently, the same gene-for-gene relationship exists in both geographical areas and, if confirmed, this would provide a useful indication of the evolutionary age of gene-for-gene relationships. The North American white pines would have had adequate horizontal resistance to their own Horizontal pathotype, but not to the allopatric pathotype.
Surviving white pines are likely to be resistant, and their selection and propagation would form an excellent project for a plant breeding clubs in the forestry department of a university. Crop
Any population of plants that is cultivated by a farmer. Crops are often defined by their ultimate purpose. Thus, cash crop, subsistence crop, food crop, fodder crop, etc. Crop architecture
The shape of crop plants and, hence, the nature of the crop itself. For example, the bean varieties of one species may have either the determinate habit, or they may be climbing vines. The latter are useful for climbing up maize plants in mixed cropping, while the former are more suitable as a pure stand, and for mechanical cultivation and harvesting. The miracle wheats and rices of the Green Revolution are dwarf varieties that can tolerate high rates of nitrogenous fertiliser without lodging. Soybeans became an important commercial crop only after types suitable for combine harvesting had been developed.
Some crops, such as potatoes, can be densely planted in order to cover the ground completely, in order to control weeds. Crop husbandry
The practice and science of the cultivation of crops. Crop loss due to parasites
The crop losses caused by parasites are usually subdivided into pre-harvest and post-harvest losses, also known as field losses and store losses, respectively. Pre-harvest losses are controlled primarily by breeding the host for resistance, and by the use of crop protection chemicals. Other methods include rotation, to reduce the incidence of soil-borne parasites, and the burning of crop residues. Post-harvest losses are controlled mainly by keeping the product dry, and by depriving the parasites of oxygen.
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