GENOTYPE X ENVIRONMENT INTERACTION, STABILITY AND COHERITABILITY OF TUBER INTERNAL QUALITY TRAITS IN POTATO ( SOLANUM TUBEROSUM   L.) CULTIVARS IN ETHIOPIA

Potato (Solanum tuberosum L.) is a crop with the potential of ensuring food and nutrition security in Ethiopia because it yields more edible energy, protein and dry matter per unit area and time than cereal crops. In Ethiopia, potato varieties were developed mainly to fit preparation of traditional foods. However, French fries and chips are the emerging products of tubers that demanded breeders to identify cultivars fit to the emerging economics of production until specific varieties are developed for specific end products. This study was conducted with the aim of identifying wide adaptable potato varieties for internal quality of tubers, and to determine stability, coheritability and correlation among traits. A total of 17 improved and two farmers’ cultivars namely, Jarso and Bete were evaluated in three locations from 2012 to 2014 using a randomized complete block design with three replications. Specific gravity and starch content of tubers were significantly influenced by the interaction of cultivar x location x seasonwhile dry matter was significantly affected only by cultivar, location and growing season. The 15 improved varieties produced tubers with >1.08 gcm^-
3,>23% and >13%specific gravity, dry matter and starch content, respectively, that were suitable for French fries and chips processing, but the two farmers’ cultivars (Jarso and Bete) with tubers <1.080 gcm^-3 specific gravity and ≤20% dry matter content failed to be processed into French fries and chips. Bubu and Gera were relatively more stable varieties in producing tubers with uniform specific gravity, dry matter and starch content across environments. The other four varieties (Belete, Gudanie, Chirro, and Gorebela) produced tubers with high mean values for all the traits that may be considered for French fries and chips making. Tubers dry matter and starch contents were highly expressed by specific gravity (R²≥0.96) with strong correlation (r≥0.98) and high coheritability (≥79.85%) of traits with specific gravity. Moreover, high coheritability was observed (86.65%) for the three traits as covariate. This suggests that tuber specific gravity is an appropriate measurement in selection of varieties to determine the internal quality of tubers for processing. The significant effect of genotype x environment interaction on specific gravity and starch content suggests the importance of testing varieties across locations over years to identify high performing and widely adaptable varieties to benefit producers, processors and other consumers.

Keywords
Chips; dry matter content; French fries; specific gravity; starch content