Entitled Response Of Apple Rootstocks (mm.111 M.9 And Mm.106) And Cultivars (anna And Jonagored) To Low Soil Ph Of Chencha

Acid soils are severe problems in many parts of Ethiopia, especially on the highland areas ofrnthe southern regions of the country. The coverage of acid soil of the country is estimated to bernabout 40% of the landmass of which 15.6% is strong acid soil. It is generally known that acidrnsoils have adverse effects on growth and yield of apple trees. In view of the wide cultivation ofrnapple in southern Ethiopia, a study was conducted to assess the effect of naturally occurringrnacidic soils and two low soil pH modified soils on three apple rootstocks (MM.111, MM.106,rnand M.9) and two apple cultivars (‘Anna’ and ‘Jonagored’). The soil pH of the study site wasrn4.9; the pH was adjusted, down to pH 3.5 (in H2SO4) and higher to pH 6.3 (in lime). Thernapple rootstocks were grown under these three pH treatments and studied for one year.rn‘Anna’ and ‘Jonagored’ cultivars grafted on these three rootstocks under similar pHrntreatments were also studied for three years. Data on vegetative growth and mineral contentrnof the different plant parts as well as yield components was followed. There were significantrngrowth differences between rootstocks. Under naturally occurring acidic soil (pH 4.9) thernvegetative growth of rootstocks were severely affected compared to soil pH of 6.3. Similarly,rnstrongly acidic soil of pH 3.5 severely decreased the growth of rootstocks in comparison withrnpH 4.9 and 6.3. Among the three rootstocks, maximum vegetative growth were recorded forrnMM.111 followed by M.9 whereas, least growth was registered for MM.106 in soil pH of 3.5.rnThe increase in growth was pH related. The effect of low pH on rootstocks elemental statusrnwas significant. In soil pH of 3.5, MM.111 showed least concentration of Al in roots and Mnrnin leaves and maximum amount of Ca, Mg, P and N in soil pH of 3.5 which makes it the mostrnthe most tolerant of low pH followed by the rootstock M.9. On the other hand, least amount ofrnCa, Mg, P, N and highest concentration of Al in the roots and Mn leaves was recorded forrnMM.106which was the least resistant of the rootstocks. Under naturally occurring acidic soil (pH 4.9) both ‘Anna’ and ‘Jonagored’ cultivars grafted on MM.111, MM.106, and M.9rnproduced reduced vegetative growth, mean number of flowers and fruits compared to soil pHrnof 6.3. ‘Anna’ and ‘Jonagored’ grafted on MM.111rootstock had the least growth with leastrnnumber of flowers and fruits were recorded on MM.106 in soil pH of 3.5. On the contrary,rnboth ‘Anna’ and ‘Jonagored’ grown on M.9 under soil pH of 6.3 produced more flower andrnfruits followed by MM.106 and least was found on MM.111. Among the two cultivars, morernnumber of flowers and fruits were produced by ‘Anna’ than ‘Jonagored’. Rootstock type hadrnsignificant influence on scion leaf nutrient accumulation. The higher concentration of Al andrnMn was found in leaf of both ‘Anna’ and ‘Jonagored’ grafted on all three rootstocks underrnnaturally occurring acidic soil (pH 4.9) compared to soil pH of 6.3. In strongly acidic soil ofrnpH 3.5, the accumulation of Al and Mn in leaves of ‘Anna’ and ‘Jonagored’ grafted onrnMM.106 was higher followed on M.9, and least was recorded on MM.111. Leaves of ‘Anna’rngrown on MM.111 accumulated significantly higher concentration of macro-nutrients, Ca,rnMg, P, and N,all within the sufficiency range for macronutrients, while, on M.9and MM.106rnthe concentrations were all in the deficiency range. In contrast, nutrient absorption ofrn‘Jonagored’ was most efficient on MM.106 in uptake of Ca, Mg, P, and N, followed by M.9rnand least on MM.111 under soil pH of 3.5. Similar findings were registered under pH of 4.9.rnThe study showed that the rootstock MM.111 is the most tolerant of acid soils and could bernused in the large acid soils of apple cultivating regions. The cultivars ‘Anna’ andrn‘Jonagored’ grafted on MM.111 had the most tolerance of acid soils and least accumulationrnof the deleterious Al and Mn in their tissues. The implications of the findings are discussedrnand recommendations on future work suggested.rnKey Words: apple, scion cultivars, rootstocks, growth, mineral content, pH levels.

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