Synthesis: the strategy of rust resistance breeding [Wheat]. Chapter 10.
1988
Simmonds N.W.
The purpose of breeding for disease resistance is to protect biomass and hence crop yield. Resistance is simply a state of less disease; and no disease (immunity) is rarely a realistic objective. Four kinds of resistance may usefully be recognized: major gene, pathotype-specific, vertical resistance (VR); polygenic, pathotype-non-specific, horizontal resistance (HR); pathotype-non-specific, major gene resistance (NR); and interaction or mixture resistance (IR). Stem rust has been well controlled worldwide for years by pyramided VR genes. Leaf rust is probably the most damaging of the three rusts at present, the genetic VR base is narrow and more epidemics must be expected. European breeders have begun to abandon VR and effective HR is recognized and beginning to be exploited. CIMMYT breeding has so far been mainly concentrated upon pyramiding VR for all three rusts, but hardly under tight genetic control. It is suggested that a reasonable/feasible shift of strategy would be a move towards research on and exploitation of HR and IR. The shift from VR to HR/IR emphasis would not come rapidly but is of very great long-term potential and practical importance.
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