Phosphites in disease management, yield and tuber quality – enhancing sustainability of potato production.

ANDREU A. B; CALDIZ D.; FORBES G.

Cuzco. Peru

Conferencia; Working Conference to Celebrate the International Year of the Potato. Potato Science for the Poor – Challenges for the New Millennium.; 2008

International Potato Center. CIP

Without fungicides, conventional potato production is not possible in many parts of the Andes.  Fungicides add to production cost and the most commonly used ones are considered environmental and human health hazards.  Phosphites are low-toxicity compounds derived from phosphorous acid and combined with different cations, such as potassium or calcium.  While phosphites are widely used on Phytophthora pathogens of many crops, they have not been adequately tested for control of potato late blight.  We have carried out phytopathologic, physiologic and biochemical studies of these compounds used for control of late blight.  Our research demonstrated a number of promising properties associated with phosphites. Calcium or potassium phosphites at 3 litre ha-1  applied to seed tubers immediately after cutting promoted early emergence, increased stem number and stem diameter, early tuber initiation and increased tuber number per plant in potato cultivars Bannock Russet, Gem Russet, Shepody, Spunta and Kennebec. Ground cover and chlorophyll content were also enhanced by phosphite treatment.  In addition to these physiological effects, phosphite treatment also resulted in greater resistance in tubers to P. infestans, Fusarium solani and Rhizoctonia solani. Protection in seed tubers was high against P. infestans, intermediate against F. solani, and low against R. solani.  Phosphite treatment of potato foliage also resulted in reduced foliage infection by P. infestans, although the level of effect was dependent on the specific cultivar.  Peroxidase and serine protease inhibitor both important in plant defence, were found to increase with phosphite application in some cases, which is consistent with the expected role of these products in stimulating host resistance. Financiado por: CONICET, UNMDP. SECYT, CIP, McCain Argentina SA, AGRO-EMCODI SA