Yield, Quality and Nodulation Studies of Kersting’s Groundnut [Macrotyloma geocarpum, (Harms) Merachal and Baudet] in the Coastal Savannah AgroEcological Zone of Ghana

ABSTRACT Two investigations were carried out in the field and laboratory to assess variation in yield and nodulation potential as well as differences in the types of Rhizobia nodulating some local accessions of Kersting‟s groundnut (Macrotyloma geocarpum Harms) Marechal and Baudet in the Coastal Savannah Agro-Ecological Zone of Ghana. The aim was to obtain information relevant to important yield and nodulation attributes of Kersting‟s groundnut under prevailing agro-ecological conditions and thereby determine the suitability or otherwise of growing the crop in the Coastal Savannah Agro-Ecological Zone. Ten local accessions of Kersting‟s groundnuts were obtained from the University for Development Studies (UDS) Nyankpala, Tamale in the Northern Region of Ghana and were evaluated under field conditions at the Biotechnology and Nuclear Agriculture Research Institute (BNARI) research farms in the Greater Accra Region. Significant variations were found in most of the quantitative characters that were measured for all the ten accessions. Yield studies conducted identified the Kersting‟s groundnut accession T8 to be the highest in both shoot dry matter production and grain yield per plot with values of 35.09 t ha-1 and 0.84 t ha-1 respectively. Nodulation studies also identified accessions T5 and T3 to be the best in %N content of roots and shoots with values of 1.43% and 3.05% respectively. The nitrogen yield was, however, highest in Kersting‟s groundnut accession T7 for both roots and shoots with values of 12.29 kg ha-1 and 1,178 kg ha-1 respectively. Again, accession T7 was superior in the total plant nitrogen yield with a value of 1190 kg ha-1. Correlation analysis revealed perfect association (r=1.0) between grain yield and dry seed and a nearly perfect association (r=0.99) between total plant nitrogen yield and nitrogen yield of shoots. Harvest index was highly positively correlated (r=0.72) with dry pod yield. Polymerase Chain Reaction (PCR) analysis was conducted for nine (9) accessions of Kersting‟s groundnut (due to lack of nodulation from one of the accessions) using three (3) arbitrary primers (ERIC 1and 2, RPO4 and RPO5)and one (1) specific primer (RPO1) to generate different amplification profiles for twenty (20) nodule bacteria isolates for each accession. The amplification profiles generated showed different banding patterns in which some ranged below 300bp to 10,000bp. The specific primer RPO1 which was a 20 nucleotide sequence primer was the most effective in generating amplification profiles. Cluster analysis was also done on the different bands that were generated to identify similarities and differences in the bacteria isolates within each accession and also between 45 nodule bacteria isolates of the different accessions. The interaccessional cluster analysis grouped the bacteria isolates into two (2) major clusters at genetic similarity of 0.7%. Both similarities and differences were observed within the accessional isolates and between the inter-accessional isolates. A number of isolates proved to be the same entities as they could not be differentiated beyond a genetic similarity of 95%. The study suggests that, Kersting‟s groundnut can be successfully cultivated in the Coastal Savannah Agro-Ecological Zone, with grain yield and nodulation comparable to what pertains in the Guinea Savannah Agro-Ecological Zone where the crop is traditionally grown in Ghana.