Potato and Tuber Crops

Botany

• The widely cultivated potato is a tetraploid with 2n=48. Basic chromosome number (x) is 12.
• Right from diploids to hexaploid species are available in potato.
• More than 75% of the species are diploids and are followed by tetraploids (15%).
• Under diploids, the cultivated species Solanum stenostomum and S. phureja are sexually fertile while S. ajanhuiri is less fertile.
• The two cultivated triploids, S. chaucha and S. juzepezukkii are more or less sterile.
• The cultivated tetraploid species S. tuberosum ssp. tuberosum and S. tubrosuni ssp. andigena are self fertile.
• Nearly all the tetraploid species are self compatible while diploids are self incompatible.
• The underground stem called stolons have nodes and internodes and grow horizontally outwards.
• And the end of stolons, tuberisation takes place.
• Under cultivation, the crop is treated as an annual with a duration of 85-90 days and tubers are harvested after yellowing and drying up of aerial stem.
• Flowers are hermaphrodite and self pollinated. S. tuberosum ssp. tuberosum produces tubers under long days or short days in the tropics or lower altitudes of 500-2000 m above MSL.
• This is distinguished from S. tuberosum ssp. andigena by less lobes leaves with wider leaflets, generally arched and set at wider angles to stem. Pedicel is thickened above.
• Solanum tuberosurm ssp. andigena produces tubers at high altitude only (above 2000 m) under short day conditions.
• It is distinguished by narrower and more leaflets which are generally petiolate.
• Leaves are set at an acute angle to stem and are generally lobed Pedicel is not thickened at apex.
• Vegetative shoot is a sympodium and each portion terminates in an inflorescence.
• Vegetative growth is continued by bud in last true leaf.
• Inflorescence is of cymose type. Flowers are actinomorphic and hypogynous with 5 calyx, 5 corolla and 5 stamens.
• Pollen sheds through pores at tips of anthers. Mature fruit is a berry. Potato tuber is a modified stem with shortened axis and poorly developed leaves.
• ‘Eye’ of tuber is a leaf-scar with a subtended lateral bud having undeveloped internodes.
• Tubers develop from sub-apical region of stolon which arises from basal nodes of stem below soil level.