Subsistence farming

Farming which feeds the farmer and his family but produces few surpluses for sale. The converse is usually called commercial farming. Similarly, one speaks of subsistence crops and cash crops. Almost all subsistence farming is now in the tropics. Subsistence crops are often mixtures of several different species , and each species is usually cultivated as a landrace. Subsistence crops are thus genetically diverse, and genetically flexible. Because they are cultivated without any use of...

Lycopersicon esculentum

Although this is botanically a fruit, it is always considered to be a vegetable in culinary and horticultural terms. It is probably the second most important vegetable after potatoes. The cultivated tomato is a self-pollinating, annual plant. It is plagued with parasite, largely because of low levels of horizontal resistance resulting from a century of the vertifolia effect. Much breeding has taken place in the past, but there has tended to be a very rapid turnover of cultivars...

Ginger

Globodera rostochiensis A cyst-forming nematode, known as the 'golden nematode', that is a serious pest of potatoes and tomatoes. Glomerella spp. A poorly defined genus of fungi, which are often the perfect i.e., sexual stages of Colletotrichum. Gluten The main protein in wheat flour. Gluten allows wheat dough to stretch and this makes the production of bread possible, by allowing gas bubbles to develop in the dough from fermentation by yeast. Glycine max The soybean,...

Grapefruit

Most grasslands are natural, and sown grassland pasture is a relative new concept in agriculture. Natural grasslands are known variously as savannah, prairie, pampas, scrub, veldt, chaparral, and steppes. Grass Any member of the botanical family Gramineae. This family includes the cereals, the fodder grasses, sugarcane, and, according to some taxonomists, the bamboos. Green manure A crop grown specifically for improving the soil by being ploughed into the soil while still green. Green manures...

Viviparous

Giving birth to live young, as opposed to laying eggs. Many aphids, and other insects, are viviparous, and this increases their rate of population growth considerably, making them r-strategists. Voandezia subterranea Bambara groundnut. This is a minor indigenous African crop with edible seeds that are formed underground like peanuts. There is probably scope for improvement by local plant breeding clubs. Vulnerability Crop vulnerability is defined as susceptibility to an absent, foreign parasite...

Fagopyrum spp

This one of the pseudo-cereals. Three species are cultivated. Fagopyrum esculentum is the common buckwheat, F. cymosum is the perennial buckwheat, and F. tataricum is the Tartary buckwheat. The buckwheats are a very ancient crop originating in China. They are not very important commercially but they have persisted agriculturally for many millennia. They are open-pollinated and amenable to general improvement by amateur breeders using recurrent mass selection . There is room for...

Pollen mother cell

The cell which, as a result of meiosis, becomes the mother of pollen cells in an anther. The pollen mother cell of some crops can be used to produce a haploid plantlet for later doubling of the chromosome number into a doubled monploid. Not a technique for amateur breeders . Pollinating insects Insects that pollinate plants. These are usually bees which are attracted to flowers by the offer of honey, but many other species of insects are involved in a wide variety of specialised flowers, such...

Ipomea batatas

This crop originated in tropical South America. It was taken by Polynesians to Fiji and New Zealand, where it is known by its Peruvian name 'kumara'. The Portuguese took it to Africa and the Far East where it is known by its Caribbean name of 'batatas', which is the origin of the English word 'potato'. And the Spanish took it from Acapulco to the Philippines where it is known by its Mexican name of 'camote'. It is now one of the more important tropical food crops. Although it...

Plant quarantine

The isolation of newly imported plants to ensure that they are not introducing any foreign parasites. The term quarantine may refer to the quarantine station itself, or to the process of testing and purifying the plant material. Plantain In the tropics, a plantain is a starchy banana that is eaten cooked. In the industrial countries a plantain is a large sweet banana that is eaten raw. Plantation forest Man-made forest in the sense that the tree species used, their planting densities, and other...

Hydroponics

The cultivation of plants in a nutrient solution instead of in soil. This technique is used mainly in greenhouses, and it is particularly useful for single seed descent. The plant roots can be suspended directly in the solution, or in inert gravel wetted with the solution, or inside flattened, plastic, tubular, film that is lying on the ground. In the last case, the plant grows through a small hole in the film, and nutrient solution is pumped continuously through the tube. The advantages of...

Terracotta pots

Flower pots made of terracotta baked clay are more expensive than plastic pots, but they provide a superior aeration to plant roots. Tetraploid A cell or plant with four sets of chromosomes. A tetraploid usually develops from a more normal diploid , by an accidental doubling of its two sets of chromosomes. See also Doubled monoploid, Haploid, Auto-polyploid, Allo-polyploid. Thea assamensis Often called Camellia assamensis, this is the tea of India and Sri Lanka Ceylon . It contains considerable...

See Brassica alba Single seed descent SSD

A quick method of producing pure lines in crops that are inbreeding, and seed-propagated, such as many cereals and grain legumes. A breeding population may contain many individuals that are both genetically diverse and heterozygous. A single self-pollinated seed is taken from each individual and is grown to maturity. This process is repeated up to six times. Each individual becomes more or less homozygous, but the population is still diverse. The best individuals are selected and kept as new...

Recurrent mass selection

The breeding method of the Biometricians, designed to increase the levels of desirable, quantitative variables by changing the frequency of polygenes. In each screening generation, the best individuals are selected, and they become the parents of the next screening generation. This process is repeated for as many generations as necessary, but the rate of progress declines dramatically after a few generations. See also early selection, Family selection, Late selection, Pedigree breeding,...

Cimex lectularius

A flat, wingless, reddish-brown, hemipterous bug, known as the bed bug, of interest in that the natural pyrethins in Chrysanthemum cineriifolium have remained a stable insecticide after centuries of use in Dalmatia. CIMMYT Centro Internacional de Mejoramiento de Maiz y Trigo. Located near Texcoco, in Mexico, this is the home of the miracle wheats, and it is a bastion of pedigree breeding and single-gene resistances. With IRRI, these are perhaps the best examples of autocratic plant breeding, as...

Amateur Plant Breeders Handbook

Robinson ISBN 0-9731816-2-1 This guide is intended for amateur plant breeders, usually members of a plant breeding club, who need a quick reference to terms that they may encounter in the course of conversation or reading. For readers who enjoy browsing, the guide should also be a source of information for anyone wanting to get away from the modern prejudices that favour single-genes, genetic engineering, and crop protection chemicals. It is also a guide for organic farmers, and for...

Habgood nomenclature

This nomenclature uses the numbers of the binomial expansion i.e., 20, 21, 22, 23, etc., with arithmetic values of 1, 2, 4, 8, etc. . Each binomial number has an arithmetic value that is double that of its predecessor. The sum of any combination of binomial numbers is unique. For example, the sum 21 can be obtained only by adding 16 4 1, and no other combination of binomial numbers can add up to this sum. The nomenclature can be applied to matching pairs of vertical genes. Each pair of matching...

Pure line

A cultivar of a seed-propagated, inbreeding species in which all the individuals are effectively identical and are almost homozygous. A pure line thus 'breeds true to type'. It is produced by self-pollinating the best heterozygous individual in a mixed breeding population for several generations. In each generation, the progeny show a reduced variability, and the process is repeated 4-6 times until no further variability is apparent. See also Single seed descent. Pyrenophora This is the Latin...

Cucumis sativus

This species originated in India. There is a wide range of cultivar. The so-called 'English' cucumber has long fruits that are used mainly in salads and sandwiches. Pickling cucumbers have small fruits and are pickled as gherkins. The 'Sikkim' cucumber of India has reddish-brown fruits. All members of this species are monoecious, annual herbs, and some are parthenocarpic. There is considerable scope for recurrent mass selection by amateur breeders. Cucurbita maxima The...

Linseed

Linum usitatissimum Flax and linseed. This species is a self-pollinating annual. There are three categories of cultivar in this crop. Flax cultivars tend to be tall, with few branches and flowers. The stems are retted to produce linen. Linseed cultivars are relatively short, many-branched, and many-flowered, they produce seed used for the production of linseed oil. This oil was originally in great demand for the manufacture of paint, but it has now been almost totally...

Beta vulgaris

This species, which belongs to the family Chenopodiacea, has been domesticated into sugar beet, garden beets beetroots , fodder beet, mangolds, and chards. It is open-pollinated and breeding is based on recurrent mass selection. The German chemist Marggraf first observed sugar in fodder beets and his pupil Achard started improving the crop and developing extraction techniques. Napoleon encouraged beet sugar production during the British naval blockade, which prevented the import of cane sugar...

Vertical resistance ultimate function

It appears that the ultimate function of vertical resistance is to reduce the population explosion of an r-strategist parasite, which is usually a parasite with a very rapid asexual reproduction. The reduction is normally achieved by reducing the frequency of allo-infections that are matching infections. However, in some pathosystems, the reduction is achieved by preventing or reducing the reproduction of the parasite. See also Quantitative vertical resistance. Vertical subsystem A subsystem of...

Spinacia oleracea

Spinach, a member of the Chenopodiacea family. A potherb crop with complex genetics that is not generally recommended for amateur breeders Spine A microscopic, reproductive body of fungi, bacteria, and other organisms. Spores may be produced either sexually or asexually. They have the same reproductive, dissemination, and survival functions as the seeds of higher plants, except that asexually produced spores do not exhibit sexual recombination and variation. Sport Mutants within a clone are...

Cynara scolymus

This Mediterranean crop is a perennial thistle and is vegetatively propagated, because true seedlings are very variable. Cynodon dactylon Star grass, also known as Bermuda grass or Bahama grass. One of the most widely dispersed grasses in the tropics and subtropics, extending even to S.W. England. While it can be a serious weed, with fast-growing rhizomes and runners, it can be useful as both a pasture grass and a turf grass. It is usually propagated vegetatively, but some...

Dizygotic

Dizygotic twins develop as two separate embryos produced by two separate ova fertilised by two separate sperm. Also known as fraternal twins. See also Monozygotic. DNA Di-ribo-nucleic acid. The protein which encodes genetic information, and controls all things inherited. In plants and animals, the DNA is located in the chromosomes. Dodder The process by which ancient cultivators changed wild plants into crop plants by artificial selection. Usually, domestication was a very gradual process in...

Cuminum cyminum

A member of the botanical family Umbelliferae, cultivated in S.E. Europe, North Africa, India, and China. The seeds are used for flavouring curry powder and other mixed spices. Curcuma domestica Turmeric. This genus is native to S.E. Asia and is a member of the ginger family, Zingiberaceae. The rhizomes provide a yellow dye, and a flavouring essential to all curry powders. It is one of those crops in which true seeds are not produced, and its ancient clones are a useful example of the...

Greenhouse cooling

The cooling of a plant breeding greenhouse in the tropics can be difficult. The external surface of the glass or plastic can be sprayed with a heavily diluted white plastic emulsion paint in order to reduce the light absorption. Rapid changes of air, by extraction fan if possible, and the evaporation of large amounts of water, offer the most efficient and the most economical cooling. Refrigeration is far too expensive and should not be contemplated. Greenhouse effect This is a geophysical...

Artichoke Jerusalem

Artificial fertilisers The term 'fertilisation' has two meanings in agriculture. It can mean sexual fertilisation of either plants or animals, or it can mean manuring of crops. Fertilisers used for manure are divided into the two categories of organic and artificial. Organic manures are either the excrement of farm animals, usually known as farmyard manure F.Y.M. or stable dung, bone meal, or quarried deposits of fish-eating bird excrement, known as guano. Artificial...

Citrus paradisi

Now popular as a breakfast dish, this mildly bitter, acidic fruit is one of the largest citrus fruits. It is of relatively recent origin and is thought to be a chance hybrid between two other Citrus spp. The name 'grapefruit' was apparently used for the first time in Jamaica in 1814, but its etymology is obscure. Citrus reticulata Mandarin, or tangerine. Often known as the 'loose-skinned' oranges because of their easy peeling, these fruits are used mainly as a dessert. They probably...