Variety Mixtures/Cultivar Mixtures/Multilines
Cultivar mixtures are defined as ‘mixtures of cultivars that vary for many characters including disease resistance, but have sufficient similarity to be grown together’. Cultivar mixtures do not cause major changes to the agricultural system, generally increase yield stability, and in some cases can reduce pesticide use.
Cultivars used in the mixture must possess good agronomic characteristics and may be phenotypically similar for important traits including maturity, height, quality and grain type, depending on the agronomic practices and intended use. Cultivar mixtures in barley for the control of powdery mildew are an example of phenotypically similar mixtures, whereas red- and white-grained sorghum mixtures used in Africa are an example of phenotypically different mixtures.
The principles driving use of variety mixtures for disease control are soundly based in ecology. Epidemics are the exception in natural and semi-natural ecosystems, reflecting the balance derived from the co-evolution of hosts and pathogens. However, in modern agriculture in particular, this balance is far from equilibrium, and epidemics would be frequent were it not for highly effective pesticides and a plant breeding industry which introduces new cultivars to the market with new or different resistance genes. Such a situation is generally profitable when commodity prices are high, but it is costly and rates very poorly on sustainability and ecological or environmental parameter scales. This chapter describes theoretical, experimental and practical results obtained using mixtures of crop cultivars for disease suppression.
KeywordsPowdery Mildew Leaf Rust Stripe Rust Susceptible Plant Pure Stand
- Bowden R, Shoyer J, Roozeboom K, Claasen M, Evans P, Gordon B, Heer B, Janssen K, Long J, Martin J, Schlegel A, Sears R, Witt M (2001) Performance of wheat variety blends in Kansas. Extension Bulletin No. 128, Kansas State University: College of Agriculture (www.oznet.ksu.edu/library/crpsl2/SRL128.pdf)
- Browning JA, Frey KJ (1981) The multiline concept in theory and practice. In: Jenkyn JF, Plumb RT (eds) Strategies for the control of cereal disease. Blackwell Scientific, London, pp 37–39Google Scholar
- Day KL (1984) The effect of cultivar mixtures on foliar disease and yield in barley and wheat. MSc thesis, University of New Castle, Upon, TyneGoogle Scholar
- Finckh MR, Mundt CC (1992) Plant competition and disease in genetically diverse wheat populations. Oecologia 91:82–92Google Scholar
- Fitt BDL, McCartney HA (1986) Spore dispersal in relation to epidemic models. In: Leonard KJ, Fry WE (eds) Plant disease epidemiology, vol 1. McMillan, New York, pp 311–345Google Scholar
- Gacek E (1997) Summarized variety mixture information given to polish farmers. In: Wolfe MS (ed) Variety mixtures in theory and practice. European Union Variety and Species Mixtures Working Group of COST Action 817. Online at: http://www.scri.ac.uk/research/pp/pestanddisease/rhynchosporiumonbarley/otherwork/cropmixtures/varietymixtures
- Jeger MJ, Griffiths E, Jones DG (1981a) Disease progress of non-specialized fungal pathogens in intraspecific mixed stands of cereal cultivars. I. Models. Annu Appl Biol 98:197–198Google Scholar
- Lannou C, de Vallavieille-Pope C (1997) Mechanisms of variety mixtures for reducing epidemics. In: Wolfe MS (ed) Variety mixtures in theory and practice. European Union Variety and Species Mixtures Working Group of COST Action 817. Online at: http://www.scri.ac.uk/research/pp/pestanddisease/rhynchosporiumnbarley/otherwork/cropmixtures/varietymixtures
- Leonard KL (1969) Factors affecting rates of stem rust increase in mixed plantings of susceptible and resistant oat varieties. Phytopathology 59:1845–1850Google Scholar
- Mertz U, Valenghi D (1997) “Extenso” production and cereal mixtures in Switzerland. In: Wolfe MS (ed) Variety mixtures in theory and practice. European Union Variety and Species Mixtures Working Group of COST Action 817. Online at: http://www.scri.ac.uk/research/pp/pestanddisease/rhynchosporiumonbarley/otherwork/cropmixtures/varietymixtures
- Moreno Ruiz G, Castillo Zapata J (1990) The variety Colombia: a variety of coffee with resistance to rust (Hemileia vastatrix Berk and Br). CENICAFE, Chinchina-CaldasGoogle Scholar
- Munck L (1997) Variety mixtures: 19 years of experience in Denmark. In: Wolfe MS (ed) Variety mixtures in theory and practice. European Union Variety and Species Mixtures Working Group of COST Action 817. Online at: http://www.scri.ac.uk/research/pp/pestanddisease/rhynchosporiumonbarley/otherwork/cropmixtures/varietymixtures
- Mundt CC (1989) Modeling disease increase in host mixtures. In: Leonard KJ, Fry WE (eds) Plant disease epidemiology, vol 2. McGraw Hill, New York, pp 150–181Google Scholar
- Mundt CC (1994) Use of host genetic diversity to control cereal diseases: implications for rice blast. In: Zeigler RS, Leong SA, Teng PS (eds) Rice blast disease. CAB International, London, pp 293–308Google Scholar
- Newton AC, Guy DC (2008) The effect of uneven, patchy cultivar mixtures on disease control and yield in winter barley. Field Crop Res 110:225–228Google Scholar
- Wolfe MS (1988) The use of variety mixtures to control disease and stabilize yield. In: Simmonds NW, Rajaram S (eds) Breeding strategies for resistance to the rust of wheat. CIMMYT, Mexico, pp 91–100Google Scholar
- Wolfe MS (1992) Barley diseases: maintaining the value of our varieties. In: Munk L (ed) Barley genetics, vol VI. Munksgaard International, Copenhagen, pp 1055–1067Google Scholar
- Wolfe MS (1997) Variety mixtures: concept and value. In: Wolfe MS (ed) Variety mixtures in theory and practice. European Union Variety and Species Mixtures Working Group of COST Action 817. Online at: http://www.scri.ac.uk/research/pp/pestanddisease/rhynchosporiumonbarley/otherwork/cropmixtures/varietymixtures