Maize is commonly classified into five groups based on the amount, quality and arrangement of kernel endosperm. This classification is in use for such a long time, its origin is not obvious.
1. Dent:
Kernels have very hard, vitreous, horney endosperm at the side and back but the central core is soft and floury. This central core extends to the top of the kernel and collapses upon drying, resulting in the distinctive indentation. This type dominates USA production.
2. Flint:
Kernels have very hard, thick, vitreous endosperm that surrounds a small, granular endosperm center. Kernels are round and smooth, with no indentation of the crown at maturity. Almost no flint maize is produced in USA.
3. Floury:
Kernels contain soft, essentially not-vitreous endosperm. Kernels can be easily ground. Kernels shrink more or less uniformly and, therefore, no denting occurs. It is grown in South America.
4. Pop:
It is an extreme form of flint maize. Kernels are small, rounded and very hard. It is grown as specialty maize around the word.
5. Sweet:
Kernels are translucent and dry to a wrinkled condition. It differs from dent type by only one recessive gene (su), which prevents the conversion of sugar to starch.
Based on the crop duration, maize cultivars are classified into five groups.
1. Full Season Maturity:
Cultivars mature in 100-110 days or even more. They may be rainfed or irrigated (Ganga 5, Ganga 9, Deccan 103, Him 123).
2. Medium Maturity:
Cultivars maturing in 85-95 days and suit well to regions with assured rainfall (composites Taru and Azetic).
3. Early Maturity:
Cultivars maturing in 80-85 days such as Humics. Suitable for sole and intercropping.
4. Very Early Maturity:
Cultivars maturing in 75-80 days include composites such as Diara 3 and D 765. Suited for summer season or intercropping in rainfed conditions.
5. Extra Early Maturity:
These are suited for rainfed conditions at high altitudes (> 2500 m MSL) with low temperature (composite Auli belongs to this group).
In India, mostly cream yellow to orange flint types are grown. Pop and sweet corns are grown only to a limited extent. Dent type is grown around Udaipur.