Search Results
Abstract
Layering is a common commercial method of propagating plant material, particularly plants such as currants and gooseberries, which reproduce naturally in this manner. European nurserymen have used layering extensively for the propagation of ornamental schrubs and trees (5). Mound or stool layering (stooling) is a method which involves cutting a plant back to the ground during the dormant season and mounding soil or other media around the base of the newly developing shoots to encourage roots to form on them (1, 2). Stooling is the most common method of propagating clonal rootstocks (4) especially for material, such as some East Mailing, Malling-Merton and Malus robusta apple stocks that are not always easily rooted as cuttings.
Abstract
Diagnosis and Recommendations Integrated System (DRIS) norms for trees on dwarfing rootstocks were derived from a 7-year fertilization trial on a Blanford loam (coarse loamy, mixed, frigid Typic Fragiorthod) in southern Quebec. ‘Morspur McIntosh’ (Malus domestica Borkh.) scions budded on M.7, M.26, Ott.3, or M.9 dwarfing rootstocks received 12 fertilization regimes involving N-, P-, K-, Ca-, and Mg-based materials applied at three rates each. Top yielding trees on Ott.3 had lower Mg concentration in their leaves than those on other rootstocks. Year-to-year variation of DRIS norms led to yearly defined DRIS norms. Annual yields can be used instead of cumulative yields to generate DRIS norms, especially from the 6th year after planting. If tissue samples are collected at the appropriate sampling period, incorporating the dry matter index into the nutrient balance equation (M-DRIS) of orchard trees helps to separate limiting from nonlimiting nutrients and also integrates numerical information on nutrient concentrations and nutrient ratios. These concentrations and ratios are commonly diagnosed independently or concomitantly with the sufficiency range approach and with DRIS, respectively. M-DRIS may be particularly useful when available critical values are not fully satisfactory, as was the case in this investigation.
Abstract
One-year old trees of ‘Spartan’ and ‘Delicious’ apple (Malus domestica Borkh.) on 4 clonal rootstocks were cut to 3 scion nodes and transferred to an aerated Long Ashton full nutrient solution containing 45Ca. Treating the axillary buds with 6-benzylamino purine plus gibberellic acid (BA + GA3) resulted in a small increase in number, fresh weight, and total length of new shoots. Total area of new leaves per tree was unaltered. The BA + GA3 treatment significantly reduced the 45Ca content of the “new shoots” fraction and the total amount of 45Ca absorbed by the treated trees. ‘Spartan’ trees absorbed and transported more 45Ca than did ‘Delicious’ and there was no significant interaction with growth regulators. Of the rootstocks, Mailing Merton (MM) 111 was less efficient than Mailing (M) 26, M 7, or MM 106 in transporting 45Ca across the graft union to either scion cultivar. Growth-regulator-treated trees on M 26 roots absorbed significantly less 45Ca than did comparably treated trees on MM 106 or MM 111 roots.
Abstract
Softening of ‘McIntosh’ apples (Malus domestica Borkh.) during storage was reduced by dipping fruit 2 days after harvest in 4% CaCl2 solution (40 g of commercial CaCl2 in 1 liter of water). The addition of Keltrol, a commercial food thickener, at 3 g/liter to retain more Ca solution on the fruit increased the effectiveness of the treatment. After 4 months storage at 0°C, fruit treated with CaCl2 and with CaCl2 plus Keltrol was 0.30 and 0.56 kg firmer by the pressure test than untreated fruit.
A 12-week greenhouse experiment was undertaken to test the efficiency of inoculation of vesicular-arbuscular mycorrhizal fungi on four apple (Malus domestica Borkh) rootstock cultivars: M.26, Ottawa 3 (Ott.3), P.16, and P.22. The plants were grown in soil from an apple rootstock nursery, containing high levels of extractable P (644 kg Bray/1 ha-1). Inoculation treatments were Glomus aggregatum Shenck and Smith emend. Koske, G. intraradix Shenck and Smith, and two isolates of G. versiforme (Karsten) Berch, one originally from California (CAL) and the other one from Oregon (OR). Mycorrhizal plants were taller, produced more biomass, and had a higher leaf P concentration than the uninoculated control plants. Mycorrhizal inoculation also significantly increased the leaf surface area of `M.26' and `Ott.3' compared to the control. Glomus versiforme(CAL)-inoculated plants generally had the best nutrient balance, the greatest final height and shoot biomass, and produced an extensive hyphal network. All the mycorrhizal plants had similar percentages of root colonization, but the size of the external hyphal network varied with fungal species. Glomus versiforme(OR) had a larger extramatrical phase than G. aggregatum and G. intraradix. Mycorrhizal efficiency was associated with a larger external hyphal network, but showed no relation with internal colonization. Despite the high P fertility of the soil used, growth enhancement due to mycorrhizal inoculation was attributed to improved P nutrition.
Herbicides are increasingly used in orchards. Since apple trees strongly depend on mycorrhizae, the effects of three commonly used herbicides on the host plant and endophyte were examined. Symbiosis between tissue-cultured P16 apple rootstocks and Glomus versiforme (Karsten) Berch was established under greenhouse conditions. Simazine (1, 2, 10, and 20 μg a.i./g), dichlobenil (1, 5, 10, and 25 μg a.i./g), paraquat (0.5, 1, 10, and 100 μg a.i./g), or water was applied to mycorrhizal and nonmycorrhizal plants as a soil drench. The response of mycorrhizal plants to herbicide was greater, and the relative elongation rate was more sharply reduced in mycorrhizal (76%) than in nonmycorrhizal plants (33%). Six weeks after herbicide application, dry mass reduction due to herbicides was similar (39% and 36%) for mycorrhizal and nonmycorrhizal plant shoots, respectively, while root dry mass reduction was larger for mycorrhizal (63%) than nonmycorrhizal plants (46%). None of the herbicide treatments affected root colonization. However, an in vitro hyphal elongation test with G. intraradices Schenck & Smith and herbicide-amended (0, 1, 10, 100, and 1000 μg a.i./g) gellan gum solidified water showed that either dichlobenil or paraquat, even at the lowest concentrations, could significantly reduce hyphal elongation. Simazine did not affect hyphal elongation in vitro, a result suggesting that improved absorption capacity of mycorrhizae explains, at least in part, the increased phytotoxicity of some herbicides. It was found that plant mortality was higher among mycorrhizal than nonmycorrhizal apple trees for all herbicide treatments. The increased CO2 assimilation rates of dichlobenil-treated mycorrhizal plants contrasted with the decreased rates of control plants measured 1 week after dichlobenil treatment. This indicates a physiological interaction between mycorrhizal colonization and dichlobenil in the toxic response of apple plants. Chemical names used: 2-chloro-4,6-bis-ethylamino-s-triazine (simazine), 2,6-dichlorobenzonitrile (dichlobenil), 1,1'-dimethyl-4,4'bipyridinium (paraquat).