Submitted to: In Vitro Cellular and Developmental Biology - Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 3, 2013
Publication Date: April 19, 2013
Citation: Wada, S., Niedz, R.P., De Noma, J.S., Reed, B.M. 2013. Mesos components (CaC12, MgSO4, KH2P04) are critical for improving pear micropropagation. In Vitro Cellular and Developmental Biology - Plants. 49:356-365. Interpretive Summary: The USDA-ARS National Clonal Germplasm Repository collection of tissue cultured plants contains over 200 pears in 18 species. Due to the wide genetic diversity of this collection there is also a diverse response to growth on standard tissue culture media. An initial study of mineral nutrition with five mineral stock solutions [ammonium nitrate, potassium nitrate, mesos (calcium, magnesium and phosphorous) , minors and iron] found that the mesos factor affected the most responses and the most genotypes. This study was designed to optimize the three mesos components for 10 pears in six species. Factors evaluated included overall quality, leaf characters, shoot multiplication and shoot height. Short stature, leaf spots, edge necrosis and red or yellow coloration were some of the main symptoms of poor nutrition in these diverse pears. Increased concentrations of all three constituents of the mesos solution decreased leaf symptoms and significantly increased overall plant quality for most of the pears. Treatments with higher concentrations all three chemicals produced the best quality ratings for eight of the 10 genotypes. The remaining pear species required one or two of the chemicals at higher rates for the best quality.
Technical Abstract: The USDA-ARS National Clonal Germplasm Repository in vitro collection contains over 200 pear accessions in 18 species. Due to the wide genetic diversity of this collection there is also a diverse response to growth on standard tissue culture media. An initial study of mineral nutrition using a systematic response-surface approach with five Murashige and Skoog (MS) medium mineral stock solutions, found that the mesos factor (CaCl2, MgSO4, KH2PO4) affected the most plant responses and the most genotypes and additional study was needed to optimize these three mesos components for a wide range of genotypes. A surface response experimental design was used to model the optimal responses for factors including overall quality, leaf character, shoot multiplication and shoot height. Short stature, leaf spots, edge necrosis and red or yellow coloration were the main symptoms of poor nutrition in shoot cultures of 10 diverse pears in six species. The growth morphology, shoot length and multiplication of these pear shoots could be manipulated by adjusting the mesos components. Suitable combinations of the meso nutrients were determined that produced both an optimum shoot number and a reasonable shoot length in addition to general good plant quality. The highest quality for the majority of genotypes, including five P. communis cultivars, P. koehnei, P. dimorphophylla and P. pyrifolia ‘Sion Sz Mi’, required higher concentrations (>1.5X-2.5X) of all the components compared to MS medium. ‘Capital’ (P. calleryana) required high CaCl2 and MgSO4 with low KH2PO4 and for ‘Hang Pa Li’ (P. ussuriensis) low CaCl2 and moderate to low MgSO4 and KH2PO4 produced high quality shoots. Optimization of nitrogen components and the effect of an optimized medium on rooting are in progress.