Glossary Plant Breeding

variance, r = number of replication, and t = table value of t at error degree of freedom
and 5% probability level.
Crop Simulation Model. A model used to study the interactive response of various
growth factors on crop yields. It is perceived as a black box in which we feed a
minimum number of data set relating to crop, soil, weather and other variables. The
model will then utilize this input data set in calculating various growth processes
using established quantitative relationships and give us the required information
regarding the daily growth and development of the crop, etc. and the simulated final
yield of the crop. In this endeavour, of course, computer plays an important role. In
the past, statistical regression type technique to forecast crop yield has been used on
the basis of only a limited number of independent variables. However, in reality, 100
or even more variables are involved. On the other hand, simulation models are based
on more variables and more physiological processes and could be universally
applicable. Such models have already been developed for wheat, rice, maize, and the
like.
Cross. A process of bringing together genetic materials from different individuals
(genotypes) to provide for genetic recombination. Also the result of the process.
Cross Classification. A system of arrangement of various treatments in relation to one
another. If all the levels of one factor are common to each level of the other, it is
called cross classification (for example, testing v varieties in r replications).
Cross Inoculation Group. Host specificity of a Rhizobium strain. A particular
Rhizobium species has a particular legume host(s). For example, Rhizobium phaseoli
infects mung bean, whereas Rhizobium meliloti infects Melilotus alba.
Crossing Over. The exchange of corresponding segments between any two non-sister
chromatids of a pair of homologous chromosomes during meiotic prophase. Its
genetic consequence is the recombination of linked genes, that is, crossing over is the
cause and recombination is the effect.
Crossover Modifier. Any gene or chromosomal structural change increasing or
decreasing the crossing-over frequency. Reduction in crossing-over frequency is
observed more frequently than its enhancement. With rare exceptions, all structural
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