Relationship between soil extractable boron and tissue concentrations in Rosaceae shrubs in Utah

Native species are distributed among a broad range of soil and environmental conditions and vary widely in boron (B) content. Soil B tests have been used often, but inconsistently, to characterize the supply of B to cultivated crop species; however such tests have never been correlated with B concentrations in native species. This study was designed to determine (a) how well three soil B extraction procedures (hot water, pressurized hot water and DTPA-sorbitol extraction) predict tissue B concentrations in three native Rosaceae shrubs [serviceberry (Amelanchier utahensis), chokecherry (Prunus virginiana), and Woods' rose (Rosa woodsii)]; (b) the effects of other soil factors (soil pH, percent organic matter and percent clay) on availability of soil B to the forgoing species; and (c) if mature leaf sorbitol concentrations are correlated with B concentrations in plant tissues and B availability in soils. We found that there was no significant difference among soil extraction methods used in predicting tissue B concentrations in the native species studied. The B concentrations of mature leaf, new twig, and flower alone (averaged 37.1, 21.0, and 35.2 mg B kg(-1), respectively) correlated poorly with extractable soil B (R2 < 0.28, p < 0.05). Only when soil pH, organic matter, clay content, and extractable B were included in multiple regression analyses to predict plant B concentrations, did predictions improve (R2 = 0.72, p < 0.002). Boron content of new twigs of serviceberry and chokecherry, high sorbitol producers (73 and 37 mg sorbitol g(-1) dry wt., respectively), was the variable best predicted by each of the three soil B tests. With Woods' rose, a low sorbitol producer (0.3 mg g(-1) dry wt.), mature leaf B concentrations offered the best predictable relationship. A significant relationship between mature leaf sorbitol content and plant B in chokecherry and Woods' rose was significant when soil pH was added to the regression equation. There is strong evidence that B is translocated more efficiently within serviceberry and chokecherry (high sorbitol producers) than with Woods' rose (low sorbitol producer). These observations have relevance for plant breeders searching for genetic traits that may enhance B movement and concentrations in related cultivated species.