Crop scientists use statistically controlled field trials to make all sorts of comparative measurements such as the yields of cultivars, the best spacing between rows, and within rows, the optimum fertiliser applications, and so on. The statistics are mathematically quite complicated, but modern computer software has largely eliminated this difficulty. These statistically controlled trials can be very accurate. However, the statistics are not accurate and, indeed, are positively misleading, when it comes to measuring pests and diseases. ... read more »

One of the advantages of the Open Plant Breeding Foundation is that it can operate internationally with various members exchanging information and genetic material between countries. It is a great idea for amateur breeders to cooperate internationally but, before they do so, they must respect their countries’ phytosanitary regulations, which exist to protect against crop vulnerabilities. ... read more »

This slideshow covers the basic principles in breeding crops for horizontal resistance.

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This is a slideshow that introduces the one-pathotype technique, which is a way of making sure that no vertical resistances are throwing off the results of a breeding program. It is the only aspect of horizontal resistance breeding that can be difficult for amateurs.

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Virtually all wheat breeding during the past 100 years has employed single-gene (i.e., vertical) resistances which usually provide a complete protection, but which are liable to break down to new strains of wheat parasites. One of the worst diseases of wheat is caused by a fungus called ‘stem rust’ (Puccinia graminis) and much of the world’s wheat is protected against it by a resistance gene called Sr24. ... read more »

Even though horizontal resistance will not break down like vertical resistance, it can be eroded quantitatively. This is an alarming thought for anyone who values the idea that horizontal resistance is durable resistance. However, this erosion is easily avoided, and it is unlikely to be serious if it does occur, but it is still important to understand it.

There are four kinds of erosion of horizontal resistance: ... read more »

In Hungary, during the 1950s, Dr. Istavaán Sárvári led a potato research team working on resistance to both blight (Phytophthora infestans) and virus diseases. The communist government closed down his breeding program because of a dispute over his breeding methods. We do not know what this dispute was, but it was probably the old Mendelian-v-biometrician quarrel. Dr Sárvári then returned to the Sárvári family farm and he took many of his potato lines with him. His people have continued his breeding ever since. Recently, by special agreement, the Sárvári Research Trust was established at Bangor, in Wales, and various lines were introduced to Britain as Sárpo (i.e., Sárvári + potato) cultivars with high levels of horizontal resistance to blight and viruses. ... read more »

The vertifolia effect was discovered by Van der Plank (1963) who named it after a potato cultivar of this name, in which the effect was very pronounced. The vertifolia effect is a loss of horizontal resistance which occurs during breeding for vertical resistance. Its meaning was later extended to include the loss of horizontal resistance that occurs during breeding under the protection of pesticides. ... read more »

In crop science, biological control has two distinct meanings. The first involves the deliberate importing of biological control agents to solve weed or pest problems. Classic examples are the control of weed cactus in Australia by insect parasites imported from Mexico, and the control of rabbits with the myxomatosis virus. This form of control can be extremely effective, but it is usually limited to the control of an imported, foreign pest by parasites from that pest’s centre of origin.

The second meaning refers to the use of the normal biological control agents of an indigenous pest or pathogen. These control agents may be predators, hyper-parasites, antagonistic micro-organisms, or organisms that trigger defence reactions in the host. The cultivation of such control agents for release into greenhouses can be an effective technique. ... read more »