Abstract:
Good quality seed potato (Solanum tuberosum L.) is important for high productivity in all potato production systems. The major yield gap currently constraining potato productivity in Kenya is the poor quality of seed. Insufficient and untimely supply of quality seed has led to fanners depending on informal seed system (farm- saved, local markets or neighbours) resulting low tuber yields due to seed degeneration. Potato tubers are prone to accumulate and transmit pests and pathogens to the next generation and this weakens the plant production potential. Apical rooted cuttings have been introduced to increase the efficiency of seed production. With high productivity of apical rooted cuttings, it becomes economical for seed multipliers selling seed after two to three seasons. Seed tubers are known for a long dormancy period with some varieties going up to 4-5 months to be used as seed. This has led to a dely in timely planting.Two experiments were conducted to study the effects of nutrient (in vitro) and soilless media on growth, yield and survival of potato apical rooted cuttings. In the first experiment the explants from three local potato variety Shangi, Unica and Wanjiku were cultured in Murashige and Skoog (MS) media supplemented with different concentrations of sucrose (20, 30 and 40 g L']) and gibberellic acid (GA3) (0.2, 0.5 and l.O mg L4). The study was laid out in a completely randomized design (CRD) using a 3X3X3 factorial arrangement. Analysis of variance was conducted by subjecting data to general linear model (GLM) to partition the variance component using SAS software version 9.0. After hardening plants were transferred to the greenhouse for experiment two where the plants were planted in polythene bags measuring 8><l4><l4cm filled with coco-peat + perlite, sand, coco-peat + pumice, coco-peat + venniculite and soil. The study was laid out in a randomized complete block design (RCBD) with a 3><5 factorial arrangement. MS medium with sucrose and gibberellic acid 40gL'l and 0.5 mgL‘l respectively significantly enhanced the shoot length of potato with Wanjiku being the tallest l0.3cm. The highest tuber yield (64.8g/plantlet) was recorded on Unica in coco-peat + pumice. This was followed by Wanjiku (59.8g/plantlet) and Shangi (40.8g/plantlet) in coco-peat + perlite. Shangi registered the highest number of mini tubers per plant (21) on coco-peat + perlite media. This, was however not significantly different from that of coco-peat +pumice treatment (19 tubers/plantlet). Results have shown that GA; at 0.5mgL'l and Sucrose at 40gL" can be used in shoot elongation and as a carbon source respectively in growth of local potato varieties grown in vitro. Coco-peat +perlite can be used in tuber fonnation of the local potato varieties
