EVALUATION OF GENETIC DIVERSITY OF COTTON (Gossypium hirsutum) L. LANDRACES IN NORTHERN NIGERIA USING AGRO MORPHOLOGICAL, MOLECULAR AND CYTOLOGICAL TOOLS

Abstract

Cotton (Gossypium hirsutum) is a leading non-food Agricultural and industrial fibre crop grown in many countries. In Nigeria, it is one of the main sources of foreign exchange and raw material with nutritional purpose and health benefit. In an attempt to improve the cotton plant, diversity study was carried out using agro morphological, cytological and molecular tools. Collection of cotton landraces was conducted in major growing zones in Northern Nigeria. The collected cotton land races were grown in an experimental bag of 20 litre bucket size, using a complete randomized design (CRD). Morphological as well as yield parameters such as; plant height (cm), number of monopodial branches per plant, number of bolls per plant, boll size, boll weight (g), seed index (g) and weight of lint in (g) were determined using standard protocol. Fibre quality of the cotton genotypes were determined using high volume instrument (HVI900A). Phytochemical analysis and molecular characterisation of each of the cotton genotypes were determined following already established protocols. Results obtained revealed significant variations in plant height across all weeks with Samcot 13 having the highest plant height (106.10 cm) at maturity followed by Samcot 9 (103.00 cm). The highest number of monopodial branches was observed in Samcot 8 (21.40) while the highest number of sympodial branches was observed in Samcot 11 (16.40). The highest number of bolls was recorded in Samcot 9 (31.30) while the least was recorded in Samcot 12 (19.30). Samcot 8 had the highest boll size (11.25 cm) while Samcot 11 had the least boll size (9.60 cm). The significantly highest weight of lint per plant was observed in Samcot 8 (13.66 g) while the least was recorded in Samcot 13 (6.34 g). Correlation of the agro-morphological parameters revealed significant and positively correlation of plant height with weight of bolls per plant (r = 0.628). Number of bolls per plant was significant and positively correlated with number of monopodial and sympodial branching (r = 0.579), (r = 0.709) respectively. The estimated genetic parameters of the cotton genotypes showed high genotypic and phenotypic coefficient variance (> 30). The heritability value had the values of 46.00 and 66.57 respectively and weight of lint per plant (38.17 and 50.06 respectively). Proximate and phytochemical composition also varied significantly among the genotypes; the highest crude fat was recorded in Samcot11 (18.00 %) and the highest protein was observed in Samcot 8 (22.17 %).Samcot13 recorded the highest palmitic acid (10.74 %) while Samcot 8 had the lowest (0.85 %) palmitic acid and arachidic acid (1.76 %).There was significant variation among the pollen size and mitotic chromosome count of Samcot 8 and Samcot 9 indicated tetraploid nature of chromosome 2n=4x=52. The Widest genetic dissimilarities exist between Samcot 9 and Samcot 10; with the cotton genotype being clustered into two (2) major groups. Cluster I and II, were further subdivided into A1 (Samcot 9); A2 (Samcot 8 and Samcot 11) and B1 (Samcot 12); B2 (Samcot 10 and Samcot 13) respectively. These results indicated that each identified genotype had unique and distinct characteristics. Exploitation of these identified traits in the cotton genotypes in breeding processes could aid in the improvement of the crop for the maximization of its production in Nigeria.