Growth, partitioning, and harvest index of tuber-bearing solanum genotypes grown in two contrasting peruvian environments.

Ten Solanum potato genotypes, including four primitive species and six hybrids, were grown to maturity near 230 and 3273 meters in elevation at two sites, Coast and Sierra, in Peru. Growth data, with emphasis upon tubers and leaves, were collected periodically to analyze the plant components which differed in these contrasting environments. Nine of the Solanum species/cultivars effectively partitioned dry matter into tubers with values reaching 73 to 85% of the total plant at mature harvest in the Sierra but dropping to 33 to 75% on the Coast. These harvest index differences were, however, accompanied by no consistent changes in total leaf area, specific leaf area, nor number of tuber initiated. Consistent differences did occur in having shorter plants in the Sierra and an increased tuber dry matter percentage, 20 to 28%, in the Sierra compared to 14 to 21% on the Coast. Linear relationships exist between plant tuber harvest index versus tuber yield and versus total plant dry matter on both the Coast and in the Sierra.