Glossary Plant Breeding

Resistance Mosaics. A strategy of resistance management that involves the use of a
number of cultivars, each carrying a different resistance gene, simultaneously or in
succession (that is, in space and time) in a production area. It can provide a diverse
environment to pathogens that would decrease the erosion of host resistance. It may
be fruitful if resistance genes are known, the racial composition of the pathogen
population is monitored closely and the mosaic pattern of cultivar use is controlled. In
absence of the orchestrated pattern of cultivar use, the strategy is certain to fail.
Resistance. A heritable property of a host plant that lessens the effects of parasitism. It
implies that some degree of host-pathogen interaction is always evoked. Therefore, a
resistant plant may resist the establishment of a pathogen by reducing the amount of
initial inoculum or may interfere the growth and reproduction of the established
pathogen. Thus some symptoms of disease always appear contrary to immunity
wherein no symptoms develop at all.
Resolving Power. The ability to discriminate between two points. The human eye cannot
resolve two points separated by less than 100m. The light microscope introduces a
500-fold increase in resolution over the eye, and the electron microscope provides a
500-fold increase over the light microscope.
Resource Conservation Technology. A technology aiming at conserving available
resources to maximize the output and profit in a cropping system. It includes zero-till
(no-till), raised bed furrow system, laser levelling, innovative cropping systems and
management of crop residues. The technology is scale-neutral and can be used with
advantage by all farmers. It lowers production costs through omitting tillage
operations and saving one or two irrigations. It has potential to maintain and sustain
productivity. Scientists have asserted that conservation agriculture can raise crop
yields by 20 to 50 per cent.
Restitution Nucleus. A single nucleus with unreduced chromosome number (produced
as a consequence of failure of the first or second meiotic division) or with doubled
chromosome number (owing to failure of mitosis).
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