Variation among clonal lines of potato in response to irrigation regimes in an isohyperthermic environment

Abstract Potato ( Solanum spp.) tuber yields are limited under hot tropical environments. Three field experiments were conducted in the Philippines to determine the yields of 27 diverse clonal lines with variations in moisture supply. Differences among lines in yield were interpreted in terms of intercepted radiation ( R i ) and radiation-use efficiency (RUE). The effects of irrigation regimes on these functions were associated with the maturity classification of the clonal lines. Relative reduction in tuber yield was less for early lines (15%) than for the medium- or late-maturing lines (30–35%). Low moisture supply significantly reduced tuber and total plant dry matter (DM) but not harvest index (HI). The reduction in total plant and tuber DM was attributed to low R i due to the restricted canopy size and accelerated senescence of the canopy and to small RUE tuber . The low RUE tuber (0.30–1.04 g MJ −1 ), particularly for late, unadapted, lines, was associated with late tuber formation and low HI. The results indicated that a favorable balance between time to tuber formation and achievement of a relatively large and long-lived canopy is important for satisfactory yields under moisture-limiting conditions in hot tropical environments.