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Differential Flooding Tolerance of Some Dwarfing Pear Rootstock Clones Selected from the Progenies of Pyrus Betulaefolia and P. Calleryana

Dr. Mahbub Robbani
Professor
Department of Horticulture, PSTU

Abstract/ Executive Summary:

Responses and tolerance to flooding of some newly selected dwarfing pear rootstock clones, in which P. betulaefolia Bung (PB) with its 4 dwarfing clones (SPRB) and P. calleryana Decne (PC) with its 6 dwarfing clones (SPRC) in conjunction with scion-stock combinations (using scion cv. Kosui) were investigated. The degree of flood tolerance among the rootstocks could be separated into 4 overall rankings: most tolerant (SPRB22), very tolerant (SPRB13, SPRB15, PC1, PC2, SPRC15, and SPRC20), moderately tolerant (SPRC3 and SPRC8) and less tolerant (PB seedling, PB4, SPRB1, SPRC5, and SPRC13) types. Short-term flooding for 30 d showed significantly lower shoot growth reduction and induced enough new roots in the water in PC and SPRC clones in general followed by two SPRB clones (SPRB15 and SPRB22) in particular. The 2, 3, 5-triphenyltetrazolium chloride (TTC) reducing activity in flooded fine roots was generally higher in PC than PB, but SPRB15 and SPRB22 also showed considerable TTC reducing activity until 15 d of assessment in short-term flooding. These results suggest that development of adventitious roots and its extent could be related to the flood tolerance of certain PB clones except for the higher root activity and the emergence of enough new roots during flooding.

Keywords: Dwarfing pear rootstock, Flooding tolerance, P. betulaefolia, P. calleryana

Location: Department of Horticulture, PSTU

Start Date: 01-01-2004

End Date: 01-06-2006

Program Area: Variety and Species

Commodity: Pear

Objectives:

To find out satisfactory flood tolerant rootstocks from a number of selected dwarfing clones.

Methodology:

For flooding treatment, three-year-old cuttings of the selected dwarfing clones were used. For the evaluation of scion-stock performance, Japanese pear cv. Kosui was grafted onto the selected clones in 2001, and their flood tolerance was investigated in 2002. Two sets of plant materials were prepared comprising the scion-stock combinations and the stock clones alone. All the scion-stock combinations and the clones were replicated thrice, and potted into a clay loam soil. In this experiment, two sets of control plants for both PB (PB4 clones and PB seedlings) and PC (PC1 and PC2 clones) were compared with the selected dwarfing clones. TTC reducing assay in flooded fine roots of three SPRB (SPRB13, 15, and 22) and four SPRC (SPRC5, 8, 15, and 20) plus controls (PB4 and PC1) was done at several flooding intervals (on days 0, 5, 10, and 15) according to Steponkus and Lanphear (1967) with little modifications. Fine roots of approximately 0.5 g fresh weight were taken separately from each rootstock line, cut into 1-cm pieces, submerged in TTC incubation solution (0.4% TTC, 0.1M potassium phosphate, pH 7.4). The ratio of root fresh weight to incubation solution volume was 0.1 g fresh weight: 2.0 ml. Samples were incubated in the dark at 37°C for 3 h. After incubation, 2 ml of 2N H₂SO₄ was added in the incubation solution, kept for 5 min. Roots were separated, rinsed twice with 99% ethyl acetate, and extracted in 8 ml 99% ethyl acetate with 0.5 g quartz sand. The ethyl acetate extracted formazan was detected with a spectrophotometer (Hitachi, Model 100-10) at 485 nm. A standard line was constructed by using pure 1, 3, 5-triphenylformazan (TCI, Tokyo Kasei, Japan). Formazan concentration was calculated by using the standard line and expressed as mg. g^-1 DW. hr^-1.

Source of Information: J. Japan. Soc. Hort. Sci. 75 (4): 297-305.

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The analysis of short and long-term flooding data made it possible to specify certain clones, such as SPRB15, SPRB22, SPRC15, and SPRC20 having ability to withstand better to flooding stress, and also promising for establishing a sustainable scion-stock combination in wet lands. These clones also have shown significant dwarfing effects on both Japanese and European pear cultivars. Among these clones, SPRB15 shows the most desirable traits as dwarfing pear rootstock in our experimental trials, such as precocity, higher yield and good fruit quality.

Knowledge Management: Journal