Submitted to: Society for In Vitro Biology Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2011
Publication Date: June 2, 2011
Citation: Reed, B.M., Wada, S., De Noma, J.S., Evens, T.J., Niedz, R.P. 2011. Physiological Disorders of Pear Shoot Cultures. Society for In Vitro Biology Proceedings. 47:S18-19. Interpretive Summary: Micropropagation is a tissue culture technique used to rapidly produce large numbers of plants. Growth disorders are one of the most difficult challenges in micropropagation. Little is known about the causes of growth disorders such as waterlogged leaves, shoot tip dieback, leaf spots and irregularly shaped stems. During our study of mineral nutrition to improve the growth of pear shoot cultures, we noted the effects of mineral stock solutions on these disorders. Mineral nutrient solutions, including combinations of nitrogen, calcium, potassium, phosphorous, magnesium, trace elements and iron, were tested over a range of concentrations. Five pear types were grown on each treatment combination. Data was collected and analyzed for each disorder. The analysis identified which minerals contributed to specific disorders and also the mineral combinations that remedied them. Many of the same minerals that affected poor overall shoot quality also contributed to these disorders. Increasing the concentration of one of the stock solutions eliminated most or all of the disorders for the five pear cultures.
Technical Abstract: Physiological disorders are some of the most difficult challenges in micropropagation. Little is known of the causes of plant growth disorders which include callus formation, hyperhydricity, shoot tip necrosis, leaf lesions, epinasty, fasciation and hypertrophy. During our study of mineral nutrition to improve growth of pear shoot cultures we also noted the effect of mineral stock solutions on these disorders. Five mineral nutrient factors from Murashige and Skoog (MS) salts, NH4NO3, KNO3, meso elements (CaCl2, KH2PO4 and MgSO4), minor elements (Zn-Mn-Cu-Co-Mo-B-I), and Fe-EDTA, were tested over a range of concentrations in a 5-dimensional experimental design. Five pears (Old Home x Farmingdale 87, Pyrus dimorphophylla, Horner 51, Hang Pa Li, and Winter Nelis) were grown on each treatment combination. Analysis for all genotypes identified the factors that contributed to these disorders and also the factors that remedied them. Many of the factors affecting overall shoot quality also contributed to specific physiological disorders. Leaf disorders (spotting and edge burn) were prominent when the mesos concentrations were = MS concentrations, but were also influenced by interactions with either low iron or high NH4NO3. Shoot tip necrosis varied with the genotype and either mesos or low nitrogen concentrations contributed to the necrosis. Hyperhydricity was more prominent with low mesos for some genotypes or low NH4NO3 for others. Epinasty, fasciation and hypertrophy were seen infrequently and were due either to interactions between mesos and KNO3 or to low NH4NO3. Callus was common on MS medium and appears to be increased by low NH4NO3 concentrations.