Exploring the environmental determinants of broomrape (Orobanche cumana Wallr.) geographic distribution. International Symposium on Broomrape (Orobanche spp) in Sunflower.

MILADINOVIC D., CANTAMUTTO M., VASIN J., DEDIC B., ALVAREZ D., POVERENE M.

Chisinau

Simposio; International Symposium on Broomrape (Orobanche spp.) in Sunflower; 2011

ACADEMY of SCIENCES of MOLDOVA and INTERNATIONAL SUNFLOWER ASSOCIATION

Orobanche is one of the most serious biotic constrains to sunflower crop production. In the more extended sunflower crop area of the world, distributed across Eastern Europe, the parasitic weed shows a high frequency of occurrence. The weed, native of Caucasus region, has progressively migrated to the South of the Eurasia continent. The actual invaded area reaches Spain and Israel countries. Due the usual seed exchange between macro-regions it is not clear why this weed problem is absent in other extended sunflower crop area located in South América. It is possible that the invasive process could be limited by abiotic constrains. With the aim to estimate the influence of environmental factors on the actual orobanche geographic distribution we evaluated fourteen sunflower habitats of Serbia with different natural infections levels and nine natural habitats of wild sunflower in Argentina. The altitude, latitude, longitude, mean hottest month temperature, mean coolest month temperature and average rainfall of ten habitats from Serbia showed not differences between infected and non infected soils. The natural initial infection of four soils from Serbia did not influence the orobanche attack intensity in a greenhouse experiment with artificial inoculation. Soil texture, total N, humus content, calcareous and pH have no effect on orobanche attack intensity. In this glasshouse experiment, Principal Components Analysis showed that orobanche attack intensity (parasitic tassel number per plant) was inversely associated only with P availability (AL-P2O5), but the linear relationship between both variables was no significant. When included in the database the Argentine habitats, strong differences between invaded and not invaded areas were found with respect to geographic localization, as expectable. The invaded habitats differenced by the lower cool month mean temperature, but no significant differences were found for the others climatic parameters. The soil fertility and texture of eleven soils with different natural orobanche infection showed no differences between invaded and not invaded habitats. A better understanding of the abiotic determinants of orobanche geographic distribution could help to design management’s tools to prevent the continuous increase of the invaded area and to limit the damage on sunflower in the regions actually affected by the weed.