Leaf physiological traits and its relation with sugar beet cultivar success in two contrasting environments

The aim of this study was to identify leaf physiological traits, which could be used in selecting high yielding genotypes among 12 sugar beet cultivars grown in two contrasting pedo-climatic environments. In the stressful Site 1 (high temperatures, low rainfall, heavy-textured soil), high yielders had cooler leaves (lower ΔT) and thus, transpired (E) and photosynthesized (A) more. Also, these cultivars had higher chlorophyll content, as assessed by SPAD readings, supporting that staying green under stress conditions contributes to final yield. On the contrary, in the favorable Site 2 (mild temperatures, high rainfall, light-textured soil), high yielding cultivars had higher leaf area index (LAI> 3.5-4.0). In Site 2, a negative correlation between SPAD and yields (fresh root weight-FRW and sugar yield-SY) indicated that the investment in high leaf greenness under favorable conditions is a disadvantage for sugar beet productivity. Combining data of both sites, the optimum values of physiological traits related to yields (FRW and SY) were estimated, respectively, at -0.59 to -053 ºC for ΔT, 20.37 to 19.26 μmol m-2 s-1 for A and 8.97 to 8.86 mmol m-2s-1 for E. It is proposed the use of SPAD as an easy, rapid and non-destructive screening for sugar beet high yielders under both stressful and favorable growing conditions.