Root traits and competitiveness against weeds in sugar beet

Weed control without using chemicals is strongly limiting sugar beet cultivation in a low-input and/or organic agriculture. The aim of this work was to evaluate, in two sugar beet breeding lines characterized by high (L1) and low (L2) yield, some root morpho-functional traits (root elongation rate, total root length and number of root tips) that might be useful for sugar beet competitiveness against weeds. The above traits were evaluated on eleven-day old seedlings grown on a hydroponic nutrient solution whereas root length density and weed density were measured in field trials. The most productive line L1 was characterized by superior root elongation rate, total root length and number of root tips as compared to L2 and the main sugar beet weeds. L1 also showed, under field condition, a higher root length density and a lower weed density highlighting a superior competitive ability against weeds (less number of weeds per area unit) and overall productivity. These morpho-functional traits could be useful for the selection of sugar beet lines requiring minor technical inputs for weed control and more suited to a low-input and/or organic agriculture.