2018 ASHS Annual Conference

River birch (Betula nigra L.) is a common landscape shade tree known to develop iron deficiency interveinal leaf chlorosis (IFC) when grown in high pH and CaCO₃ soils. While variation in symptomology has been observed, provenances endemic to high pH soils may not always display chlorosis. The increased interest for environmentally sustainable landscape selections could be made if additional screening was conducted to determine their potential adaptability to high pH and CaCO₃ soils. The first study (Expt. 1) evaluated open-pollinated (OP) seedlings of Iowa provenances and ‘BNMTF’ OP in an elevated pH substrate. A second study (Expt. 2) evaluated clones from selected Iowa provenances, ‘BNMTF’, ‘Cully’, and ‘BNMTF’ OP. Twice-weekly 120 mL drenches of 4.8% CaCO₃ were used to maintain an elevated substrate pH. In Expt. 1, leaf chlorophyll was reduced by 36% in elevated pH substrate (pH = 7.57) compared to the control (pH = 5.57): (16.95 and 26.39 μg·cm^-2, respectively) with differences in seed sources observed. A seed source from Bearbower Sand Prairie, Buchanan Co., IA (BSP3) had the greatest leaf chlorophyll content (25.86 μg·cm^-2) but was not statistically greater than two sources from Clemons Creek WMA, Washington Co., IA (23.90 μg·cm^-2, CCWMA1 and 22.76 μg·cm^-2, CCWMA2). Total leaf iron (Fe) concentrations were reduced by 61% for sources growing in the elevated pH substrate. In Expt. 2, leaf chlorophyll was reduced by 32% in elevated pH substrate (pH = 7.00) compared to the control (pH = 5.29); (19.40 and 28.73 μg·cm^-2, respectively). An Iowa clone, CCWMA3, had greater chlorophyll content than some other sources (26.78 μg·cm^-2) but no greater leaf chlorophyll content than ‘BNMTF’ (25.70 μg·cm^-2), a source from Ciha Fen, Johnson Co., IA (24.95 μg·cm^-2, CF3), and a source from Princeton WMA, Scott Co., IA (24.13 μg·cm^-2, PWMA2). ‘Cully’ had lower leaf chlorophyll (21.87 μg·cm^-2) than CCWMA3 and ‘BNMTF’. Total leaf Fe content was also reduced in elevated pH substrate for all sources compared to their controls. Based on our studies, these Iowa provenances did not sequester more substrate Fe in their leaves than the industry standards, but two selections (BSP3 and CCWMA3) were perhaps more Fe efficient, because they were considerably less chlorotic than ‘BNMTF’ OP and ‘Cully’. These Iowa seed sources and clones should be further evaluated in field studies to determine their extent of Fe-use efficiency in high pH soils compared to popular industry cultivars.