Glossary Plant Breeding

Maternal Effect. The environmental influence of the mother’s tissues on the phenotype
of the offspring. It may be result of nuclear genes as observed for cases like shellcoiling
example in the water snail Limnaea.
Maternal Inheritance. A type of uniparental inheritance in which all progeny have the
genotype and phenotype of the parent acting as the female. It was first discovered by
Carl Correns (1909) in his studies on four-o’clock plants (Mirabilis jalapa) forleaf
variegation (patches of green and white tissues in the leaf).
Maternally Expressed Gene. A gene that contributes to the phenotype of an offspring on
the basis of its expression in the mother.
Mating System/ Mating. Any of a number of schemes by which individuals are assorted
in pairs leading to sexual reproduction, and thus formation of zygotes.
Mating Types. The analogous terms used in lower organisms for sexes in higher
organisms. Mating types differ only physiologically, and not in the physical form.
Matriclinous. Having predominantly maternal hereditary traits.
Matriclinous Inheritance. A type of inheritance in which all offspring have the nucleusdetermined
phenotype of the mother.
Maximum Likelihood. A statistical procedure for estimating values of population
parameters from sample data. The method identifies values that have maximum
probability of being the best fitting for any given set of observations.
Mean Deviation. The sum total of average deviations (d) of individual observations
from their arithmetic mean without regard to the sign {d/N}. Though not used
frequently, it finds its greatest application in calculating combining ability effect(s) of
a given parent of/or a cross in plant breeding experiments.
Mean. Also called arithmetic mean. It is the arithmetic average and is obtained when the
number of individuals in the data divides the sum of the values of the observations (in
that data). It is usually designated by μ and x in the population and sample,
respectively. Unlike median and mode, it is affected by the extreme values. However,
it is most commonly used and preferred as it provides more information about the
central tendency than other measures.
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