Quantitative effect of root/leaf growth rate on root yield and quality parameters in sugar beet

Although the known literature does not suggest that leaf canopy and active photosynthesis are limiting factors in sugar beet growth, the partitioning of photosynthetic products into the two main plant parts (root and top) is the most critical factor affecting sugar beet yield and quality under Mediterranean climatic conditions (Greece). A three-year survey, over four growing areas, on representative commercial sugar beet fields was conducted to quantify sugar yield and root quality responses to different root and leaf growth rates. The data collected established that any differentiation regarding PTOP (Top leaf mass as a percentage of the total plant mass) was associated with corresponding differentiations in sugar yield and quality parameters for a long period of the harvesting time. Statistically significant correlations of PTOP were found in June with sugar content (- negative) and Na content of roots (+ positive) of sugar beet being harvested in successive periods of time. A higher correlation was established with the quality ratio QR (sugar content to Na content of roots). The top leaf differentiation was found to be influenced by the nutritional status of the sugar beet plants and, moreover, by any factor regulating the quantitative plant response to certain nutrient levels (location, year, interactions). Average values of the QR and the regression rate (slope) of sugar content as a function of Na content of roots, were used as indices to classify sugar beet growing areas on the basis of beet technological values. Evaluation and interpretation of these indices as well as agronomic implications are discussed. Further investigations to determine local factors associated with beet quality parameters are needed.