Plant characters are of two types viz., quantitative and qualitative. These are briefly discussed below
1. Quantitative characters:
Quantitative characters are governed by several genes. Hence they are also known as polygenic characters.
Such characters are expressed in degree rather than kind. Polygenic traits exhibit continuous variation from one extreme to other and therefore, grouping into distinct classes is not possible.
In such traits, effect of individual gene is small and undetectable. Polygenic traits are highly sensitive to environmental changes.
Such characters are measured in terms of height, length, width, weight and duration. Statistical analysis of these characters is based on means, variances and co-variances.
Examples of quantitative characters are yield, days to flower, days to maturity, seed size, seed oil content, protein content etc.
2. Qualitative characters:
Qualitative characters are controlled by one or few genes and therefore called monogenic or oligogenic traits.
Such characters exhibit discontinuous or discrete variation and therefore, can be easily grouped into distinct classes.
In such characters effect of individual gene is large and easily detectable. These characters are also known as major gene characters.
Oligogenic characters are very little influenced by environmental variation. Such characters are recorded in terms of shape, surface and color.
Statistical analysis of such traits is based on ratios and frequencies. Both quantitative and qualitative characters have some similarities, e.g.
Segregations, mutation, linkage, reciprocal differences, dominance and epistasis etc. are common features of polygenic and oligogenic traits. In plant breeding, both oligogenic and polygenic characters are equally important.