Early Food Crops

Early Food Crops
The angiosperms provide most of our food crops. They first appeared in the early Mesozoic or late Paleozoic era about 200 – 250 million years ago, but fossil evidence of them is extremely limited until they began to dominate during the Cretaceous (136 – 190 million years ago). The angiosperms were the first plants to have double fertilization and the enclosure of seeds in fruit. Double fertilization provided zygotes with copious resource to help them get established and fruits attracted animals for dispersal, it was the appearance of the angiosperm that set the stage for the development our mammal ancestors.

A wide range of hypotheses implicating selection have been presented for a rapid emergence and diversification of the angiosperms. The most popular hypothesis is that the concomitant rise of pollinating insects led to powerful divergent selection as foragers and hosts developed complex relationship.

It was the angiosperms that ultimately provided us with most of our crops and their emergence predated the appearance of our species, Homo sapiens. In fact, most of our food families or their close relatives were in existence long before we began farming. The only completely new crop type to appear after the advent of agriculture was maize, Zea mays, which has an ear and tassel arrangement not found in its progenitors. In most cases, human beings did not influence the overall structure of crop species, only the size of their edible organs and their ease of harvest.

Human beings now consume a diverse array of plant structure, and at least 64 families of angiosperms and 180 genera are utilized as crops. This is a broad systematic group, but represents only a small fraction of the total number of angiosperm families (300) and genera (3000). The dicotyledons provide the highest number of crop plants; however, the bulk of the world is fed by a few monocotyledonous grains (maize, rice and wheat).
Early Food Crops

Cowpeas Production and Storage

Cowpeas Production and Storage
Cowpeas (Vigna unguiculata) are believed to have originated in India and have been spread by man to other parts of Asia and Africa and then in the seventeenth century by way of the West Indies, to the Americas. They are now grown in warm and tropical climates around the world and about 80,000 ha of the crop is cultivated in southern parts of the Unites States, particularly in California, Georgia and Texas. There is considerable variation in the appearance of cowpea according to variety: one of the most popular varieties is the blackeyed bean. About 60,000 t of dry cowpeas are produced annually in U.S.A, of which originate from the state of California, they are consumed locally and also exported to over 40 countries.

Cowpeas are moved from farm to warehouse. Scheduled fumigations with methyl bromide or phosphine protect the commodity from insect infestation. There is a zero tolerance of insects on cowpea; this results on stocks being fumigated at least four times a year to ensure that they are pest free. It is extremely rare for the crop to be marketed within the year of production, resulting in an overlap of harvest in store and subsequently an increase in the cost of pest management.
Cowpeas Production and Storage

Genetic Resource of Rice

Genetic Resource of Rice
Cultivated rices fall into two groups similar in appearance but distinguish by their different areas of origin and by the sterility of hybrids between them, indicating significant genetic separation. They are Oryza sativa, Asian rice, and Oryza glaberrima, African rice. Both are presumed to have descended from a common ancestor, perhaps O. perennis, a wild perennial species widely distributed throughout the tropics. The evolution of the two groups proceeded independently with the similar steps in each case; first, the evolution from the presumptive common ancestor, of two wild perennial, one Asian the other Africa. Each in turn gave rise to a wild annual species from which the cultivated annuals arose. Chromosome studies show that the species in the two pathways share the same genome AA, which appears to have undergone some modifications in the O. glaberrima pathway. These differences are associated with, though not necessarily responsible for, the genetic isolation between the two groups. Uncertainties exist about the precise identity of ancestral species, partly because of the absence of major genomic differentiation, which provided strong evidence of origin in other species groups such as wheat and cotton. All cultivated rices are diploids.

O. glaberrima occurs in sub-Saharan Africa, in flood plain habitats where it is sown before the floods arrive and harvested after they have receded. Upland or ‘dryland’ varieties are also grown. Although it is hardier than O. sativa, it nevertheless has been replaced by O. sativa whenever condition permit the latter’s cultivation. The greatest diversity of O. glaberrima is in West Africa.

The starting point for the differentiation of the Asian rices is perennial wild grass O. rufipogon, widely distributed in south and south-east Asia, south China, and South America, from which the annual wild species O. nivara arose. O. nivara has a wide distribution range in India, south-east Asia and Oceania. Domestication of nivara involved selection for non-brittle ears, larger plants and grain, and shorter dormancy and it probably occurred, perhaps in several independent cases, within the large area north east India, northern Bangladesh, Burma, Thailand, Laos, Vietnam and south east China. From this diffuse area origin, cultivate rice was rapidly and widely dispersed into new regions and habitats by farmers who doubtless could see the immense benefits to be gained from the addition of a cereal crop to a farming culture which up to that time had lacked one.
Genetic Resource of Rice