Sorghum cultivar evaluation for iron chlorosis resistance by visual scores

Abstract

Sorghum cultivars differ in their ability to maintain adequate production of leaf chlorophyll when grown under conditions of moderately severe iron stress. A visual test for differentiating Fe‐chlorosis resistance in sorghum cultivars was developed by growing plants in a CaCO₃, buffered nutrient solution. Nine sorghum cultivars were germinated in vermiculite for seven days before being transferred to an Fe‐stress nutrient solution buffered to pH 7.5 with excess CaCO₃. Twenty replications were grown in a growth chamber with a 26°C ‐ 15 hour light (300μE M^‐2S^‐1) and a 22°C ‐ 9 hour dark period. Leaf chlorosis was visually scored on a 0–4 rating scale after 10 days in nutrient solution and chlorophyll content was determined spectrophotometrically after extraction with 80% (v/v) acetone. Differences in leaf chlorophyll production correlated significantly with measured levels of chlorophyll in both growth chamber and field grown sorghum. Plant cultivars were readily separated into Fe‐susceptible, Fe‐tolerant, and intermediate groupings. This suggests that a visual, rating scheme which is both rapid and efficient could be readily used in evaluation of Fe efficiency in crop plants.

Key words:

• Chlorophyll
• Iron stress
• CaCO₃ buffered nutrient solution