Rhizosphere Acidification is Not Part of the Strategy I Iron Deficiency Response of Vaccinium arboreum and the Southern Highbush Blueberry

Abstract

<jats:p><jats:italic>Vaccinium arboreum</jats:italic> (VA) is a wild blueberry species that exhibits wider soil pH tolerance and greater ability for iron and nitrate uptake than cultivated <jats:italic>Vaccinium</jats:italic> species, including southern highbush blueberry (SHB, <jats:italic>V. corymbosum</jats:italic> interspecific hybrids). The ability of VA and SHB to respond to iron deficiency by rhizosphere acidification was investigated. Rooted cuttings of the VA genotype FL09-502 and SHB ‘Emerald’ were transplanted to a hydroponic system filled with complete nutrient solution. After 14 days of acclimation at 45 µ<jats:sc>m</jats:sc> iron, plants were transferred to unbuffered nutrient solutions containing 90 or 10 µ<jats:sc>m</jats:sc> iron. ‘Emerald’ and FL09-502 plants grown in 10 µ<jats:sc>m</jats:sc> iron exhibited less iron uptake and lower chlorophyll, total iron, and active iron contents than plants grown in 90 µ<jats:sc>m</jats:sc> iron. Generally, there were no species-level differences in iron or nitrate uptake. Neither FL09-502 nor ‘Emerald’ acidified the rhizosphere in either the nutrient solution or in a gel-based assay, regardless of external iron concentration. A screen of 18 additional genotypes of VA and SHB confirmed that this response is absent in these taxa. Thus, rhizosphere acidification is not part of the iron deficiency response of SHB and VA. In addition, the ability to acidify the soil is not likely to be responsible for the wider soil pH tolerance of VA.</jats:p>

Growth, Fruit Yield, Photosynthetic Characteristics, and Leaf Microelement Concentration of Two Blueberry Cultivars under Different Long-Term Soil pH Treatments

“…Brown and Draper [43] found that the rhizosphere acidification ability of blueberry was negatively correlated with the chlorosis degree of leaves; that is, the stronger the acidification ability, the lower the chlorosis degree. However, Nunez et al [3] proved that rhizosphere acidification is not part of the strategy I iron deficiency response of V. arboreum and the southern highbush blueberry grew in nutrient solution (initial pH 5.5) or agarose gels (initial pH 6.0) with nitrate as a nitrogen source. This study agreed with Brown and Draper [43], that 'Chaoyue No.…”

“…It is popular worldwide because of the high nutritional value of its fruit and its strong antioxidant capacity [1,2]. Blueberry is an acid-loving plant [3], and a suitable soil pH for its optimal growth is approximately 4.0-5.0 [4,5]. Some studies have shown that elevated pH in the rhizosphere for blueberry will lead to nutritional imbalance, leaf iron deficiency chlorosis, and a decrease in photosynthesis, thereby inhibiting plant growth and reducing yield [6,7].…”

Comparative Analysis of Rhizosphere Microbiomes of Southern Highbush Blueberry (Vaccinium corymbosum L.), Darrow’s Blueberry (V. darrowii Camp), and Rabbiteye Blueberry (V. virgatum Aiton)

“…The development of SHB cultivars was initiated by crosses between the tetraploid NHB V. corymbosum L. to Florida's native diploid blueberry species Vaccinium darrowii Camp, but later, native V. angustifolium and V. virgatum were introduced into breeding programs (Sharpe and Darrow, 1959). These efforts helped to introduce novel adaptation genes and led to the release of several commercial cultivars with improved tolerance to higher soil pH and drought (Finn et al, 1993;Nunez et al, 2015). However, despite significant progress, the expansion of SHB in the Gulf Coast region of the United States is still challenged by fluctuations in temperature, rainfall patterns, UV levels, elevated soil pH, and drought (Lobos and Hancock, 2015).…”

Ammonium Uptake Is the Main Driver of Rhizosphere pH in Southern Highbush Blueberry

“…SHB plants take up N preferentially in the NH 4 + form (Merhaut and Darnell, 1995). Although SHB plants do not acidify their rhizosphere in response to Fe deficiency (Nunez et al, 2015), other factors that affect SHB rhizosphere pH are unknown. This research aims to quantify the effect of NH 4 + uptake on SHB rhizosphere pH change.…”