Source-sink relationship in Hausa potato

Fresh tuber yield of Hausa potato [Solenostemon rotundifolius (Poir) J.K. Morton] is generally low in Nigeria, perhaps, due to a lack of balance between the source and the sink. The objective of this study was to investigate the relationship between source-potential and sink-capacity, and its effect on dry matter production and distribution, as well as on dry tuberous yield in reciprocal grafts of four accessions of Hausa potato. Four accessions of Hausa potato were used for reciprocal grafting. The degree of response of source to sink and of sink to source was determined using regression coefficient analysis. The number of tubers per plant, length and girth of tubers varied with accession, source-potential and sink-capacity. The highest source-potential was observed in accession Manchok 2. The highest sink-capacity was observed in accession Langtang. Although accession Manchok 2 had the largest source-potential with respect to dry tuber yield, the highest response of source to sink was observed in accession Bokkos 2, with regression coefficient of 0.83. Accession Langtang had the highest sink-capacity, but the degree of response of sink to source was highest in accession Bokkos 2 with regression coefficient of 3.26. The results showed that the photosynthetic capacity of accessions with large source-potentials is unlikely to be altered by change in sink-capacity. Productivity in Hausa potato may be influenced by the photosynthetic activity of the leaf canopy (source), the capacity of the plant to translocate photo-assimilates to the tuberous root (sink) and the capacity of the tuberous root to accommodate or capture the assimilates.