SOURCE:

Faculty: Biosences
Department: Botany

CONTRIBUTORS:

Ezeabara, C. A.
Okeke, C. U.
Amadi, J. E.

ABSTRACT:

Colocasia esculenta (L.) Schott belongs to the genus Colocasia Schott, of the family Araceae. It is one of the staple tuber crops of Southeastern Nigeria. Taxonomic studies of Colocasia esculenta var. antiquorum (L.) Schott Hubbard & Rehder, Colocasia esculenta var. esculenta (L.) Schott, ‘kochuo’, ‘nwine’ and ‘ogeriobosi’ were carried out. The samples were collected from the local farmers in three geographical locations of Anambra State. The third fully opened active leaves, petioles and cormels from the base were used for morphological study. The coleoptile was removed before corm was measured while petiole measurement started from the ligule. Fresh materials were fixed, sectioned and viewed under a microscope for anatomical and histochemical studies. For phytochemical, mineral, vitamin and proximate analyses, the leaves, petioles, roots and cormels were dried and assayed using standard procedures. The cormels from each variety were planted in plastic pots (90 x 145 mm), filled with sandy loam soil to a depth of 45 mm, and allowed to sprout. Fresh root tips of 15 mm were then collected at hourly intervals from 8.00 am to 3.00 pm for cytological study. Test of significance was measured using Duncan’s Multiple Range Test (DMRT). Morphologically, result showed that Colocasia esculenta var. antiquorum had large corm which was more or less orbicular in shape with numerous small round cormels whereas the corm of Colocasia esculenta var. esculenta was large and oval with few more or less cylindrical shaped cormels. The leaves of ‘kochuo’ had a purplish dot on the centre of the adaxial surface and the cormels had numerous conspicuous vertical brownish stripes on the surface. There was presence of foliaceous appendages at the veins of the abaxial surface of the leaves of ‘ogeriobosi’. It had the highest petiole length at 63.30+3.83 cm, leaf length at 49.90+3.55 cm, corm length at 8.60+0.35 cm and cormel length at 7.03+0.36 cm. ‘Nwine’ possessed yellowish-green petioles and slender cormels. ‘Ogeriobosi’ had purple petioles. Anatomically, both adaxial and abaxial leaf surfaces of all the varieties possessed anomocytic stomatal type. The arrangements of the pores in all the varieties were exclusively solitary, with the exception of pores in ‘ogeriobosi’ which were in clusters. ‘Ogeriobosi’ had the smallest cyclic polygonal vessels in the petiole varying from 120 – 216 µm in length to 96 – 168 µm in width. Histochemically, raphides were present in the petioles of all the varieties with the exception of ‘nwine’. A bar of styloid was only found in petiole of C. esculenta var. antiquorum. There was presence of druses and rosettes in petioles of ‘kochuo’ only, and crystal sands were detected only in the petioles of C. esculenta var. esculenta and ‘nwine’. Phytochemically, highest level of flavonoid, saponin and tannin detected in the leaves were found in ‘ogeriobosi’ at 0.78±0.01%, 1.41±0.01% and 0.65±0.03% respectively. The highest value of oxalate and hydrogen cyanide in the root being 1.66±0.02% and 4.93±0.04 mg/100g respectively were present in ‘nwine’. For proximate constituents, values of calcium were highest in parts of all the varieties with the exception of the root. Vitamin C content was highest in leaves, petioles, cormels and roots of all the varieties. All parts of all the varieties had considerable high level of crude protein with highest value present in the cormel of ‘ogeriobosi’ at 8.74±0.02%. Cytologically, chromosomes count of 2n=24 was observed in C. esculenta var. antiquorum, C. esculenta var. esculenta, ‘nwine’ and ‘kochuo’, whereas ‘ogeriobosi’ had 2n=28. This study supplied additional diagnostic and differential characters of C. esculenta varieties, which could be used for their identification, description and delineation. In addition, ‘ogeriobosi’ and ‘kochuo’ are proposed as new species of Colocasia; C. ezeabarae and C. ugensis were respectively, while C. esculenta var. nwine was recommended as variety of C. esculenta for ‘nwine’.