80
was effective for 1–15 years, depending on the cultivar, the area on which the cultivar
was sown, the country and the type of rust (Kilpatrick 1975 ). If a few cultivars
occupy a large sowing area, there is an increasing danger that mutant pathogen
strains will become established and break down the resistance of the cultivars
(Brennan and Byerlee 1991 ).
The technology used for wheat production undergoes constant changes, which
may exhibit opposing trends in different growing regions. In many areas fertiliser
doses are on the increase, while in many countries in the European Union the oppo-
site tendency can be observed due to environment protection concerns. The plant
protection technology may also change, either in the interests of maintaining pro-
duction levels or due to the banning of certain chemicals. Whatever changes may
occur in wheat production practice, however, there will always be a need for new
cultivars that can be optimally grown in the changed environment.
It is not unusual for the demand for new cultivars to originate from consumers or
the processing industry. People now expect to buy better quality products, so the
quality standards required by the industry are rising. New wheat-based products
from the baking, confectionery, pasta, brewing, canning, etc. industries require raw
materials with diverse composition and technological quality, and this can only be
achieved by breeding for specifi c end-uses. Breeding aims are also infl uenced by the
expansion of the wheat trade and changes in export markets.
The targeted increase in yields does not necessarily require an increase in yield
potential, since even the potential latent in existing cultivars cannot be exploited
under farm conditions (Anderson 2010 ; Patrignani et al. 2014 ). In general it can be
said that the lower the extent to which the growing environment (location, weather,
technology) satisfi es the conditions optimum for wheat, the more the actual yield
will depend on the adaptability of the cultivars rather than on their potential yielding
ability.
Numerous examinations have been carried out to determine what proportion of
the yield increase can be attributed to plant breeding, i.e., to the development of new
cultivars. The annual genetic gain demonstrated for the grain yield of wheat varies
from 0.16 to 2.3 % (Table 3.1 ). The estimates depend greatly on the length of the
period examined, the initial starting level, the size of the growing area and how
favourable the environmental and economic conditions are for breeding research
and production development.
Table 3.1 Genetic gain/year through wheat breeding in different regions
Genetic gain
% Country Period Author(s)
0.16 India 1901–1980 Sinha and Aggarwal ( 1980 )
0.48 Finland 1939–1991 Peltonen-Sainio and Peltonen ( 1994 )
0.9 Mexico 1950–1982 Waddington et al. ( 1986 )
0.74 USA 1958–1980 Schmidt ( 1984 )
1.3 Oklahoma, USA 1969–1993 Khalil et al. ( 1995 )
2.3 Hungary 1930–1986 Balla et al. ( 1986 )Z. Bedő and L. Láng