GENETIC DIVERSITY OF AFRICAN YAM (Dioscorea spp.) IN NORTH CENTRAL NIGERIA

Abstract

Yam (Dioscorea spp.) are annual crops cultivated for food in tropical and sub-tropical regions of the world. The crops are grown in Nigeria for nutritive, social and economic benefits. In spite all these importance, research on its improvement has been inadequate due to lack of sufficient genetic knowledge of the existing germplasm of the crop. Against this background, a survey and exploration were carried out to collect and characterise the available landraces of the crop germplasm in North-Central Nigeria as well as to identify elite genotypes that could be utilized for further breeding programs. Thus, 50 accessions of yam were randomly collected across the six (6) major cultivating states. The accessions were set on field using a Randomized Completely Block Design (RCBD) with five replicates per accession and morphological features were characterized. Also, analytical evaluation of the nutritional and anti-nutritional properties was conducted using standard procedures. Simple Sequence Repeat (SSR) DNA markers technique was adopted for molecular studies to determine the genetic diversity in the crop. Results showed that the highest number of accessions (21) was recorded in Niger State (NG), followed by Benue (BN) with 19 accessions, Kwara and Nasarawa were with 3 accessions each and the least (2) accessions were obtained from Kogi and FCT, Abuja respectively. Significant differences were obtained (P < 0.05) for most of the agro morphological parameters considered. Morphological evaluation showed the highest number of leaves per plant (655.30) from BNr. 063 and the least (34.10) was recorded from NGr. 019. Highest stem length (551.43 cm) was recorded from KGr. 006 and highest auxiliary branch (24.50) was obtained from KGr. 043.Highest yield for tuber length (68.98 cm), tuber breath (31.32 cm) and tuber weight (34.68 kg) were recorded from NGa. 033, BNr. 084 and NGr. 017. Mineral composition indicated that the highest moisture content (16.23 %) and highest carbohydrate content (80.77 %) were recorded in NGr. 023 and BNr. 063 respectively. Highest mineral compositions for sodium (26.22 mg/100g), phosphorus (0.55 mg/100g), potassium (16.90 mg/100g) and Iron (5.24 mg/100g) were recorded in BNr. 071, KGr. 003, NGr. 001 and BNr. 063 respectively. Accession BNr.053 yielded the highest manganese content (2.19 mg/100g) while the highest value for oxalate (10.15 mg/100g), alkaloid (0.08 mg/100g) and flavonoid (4.30 mg/100g) were obtained from BNd. 030. A total of 84 polymorphic reproducible and scorable bands. The six(6) DNA primes used yielded maximum polymorphism of 100% and all the markers produced high polymorphic Information Contents (PIC) range of 0.35-0.55. The UPMA dendrogram group the genotypes into eight (8) clusters based on the species relatedness. The high variability recorded in genotypes for both morphological and nutritional assessment in addition to high molecular and genetic advance recorded provide background information that plant breeders and researchers could exploit for the crop improvement programs of yam in the future.