SUBSTANTIAL LEAF SHEDDING - A CONSISTENT PHENOMENON AMONG HIGH-YIELDING SWEET-POTATO CULTIVARS

Four high-yielding sweetpotato [Ipomoea batatas (L.) Lam.] cultivars displayed substantial leaf shedding, under typical field production conditions, that was not due to pathological or herbivory causes. Losses ranged from almost-equal-to 45% to 60% of the total leaves formed by the normal harvest date during 2 years. There was a strong positive correlation between leaf shedding and the number of vines (r2 = 0.80) and nodes (r2 = 0.89) per plant. Likewise, positive correlations were found between leaf shedding and total dry weight (r2 = 0.67), root fresh weight (r2 = 0.65), root dry weight (r2 = 0.60), and vine dry weight (r2 = 0.68). Distinct differences were found among cultivars in dry-matter allocation within the plant. 'Jewel' allocated a lower percentage of dry matter into vines and a higher percentage into storage roots. Estimated leaf dry matter losses due to leaf shedding ranged from 1.2 to 2.6 t.ha-1. High leaf losses appear to be closely related to vigorous vine growth and subsequent shading of older leaves but did not have a negative impact on storage root yield in the cultivars tested.