DROUGHT EFFECT ON THE MORPHOLOGY, GROWTH AND PRODUCTIVITY OF POTATO GENOTYPES (Solanum tuberosum L.) IN BOLIVIA

In the Andean highlands of Tiraque, Cochabamba, Bolivia and during two consecutive years, six contrasting potato varieties were evaluated in their tolerance to drought, in semi-controlled conditions using small containers suitable for planting under a cover shed type that served as a shelter from rain. The objective was to determine the morphological mechanisms used by the potato adapt to drought and identify sensitive morphological parameters associated with crop yield. Three water regimes were applied: R0 = irrigation at field capacity (control), R1 = drought at the tuber initiation (early drought) and R2 = drought to a tuber initiation month (late drought). Morphological parameters were evaluated, growth variables, variables of damage and yield components. Large morphological differences were observed between varieties determining that early drought has a greater effect on the morphology of the plant than late drought. The morphological type of sensitive and tolerant varieties shows substantial differences between them. It was shown that in most varieties of plant height, the number of internodes, number of leaves and number of branches were the morphological variables most affected by early drought. Of all these, susceptibility to drought in the number of branches is markedly associated with the yield susceptibility of each variety. As a stricter index to choose productive material under drought conditions, it was estimated the index of "Potential susceptibility of yield" which associated with the susceptibility of branches and leaves number can be used as indicators tolerance to drought. Of these, the sensitivity of number of branches is strongly associated to the performance sensitivity, therefore, this variable can be used as an indicator of drought tolerance in potato. Moreover, it highlights the characteristics of the variety Waych'a that differs from the others in terms of its higher growth rate, increase of root rate, its capacity of recuperating after irrigation and filling their small tubers, as particular mechanisms which make it less sensitive and with more stability in drought conditions.