Adventitious Root Induction in Apple (Malus × domestica Borkh.) Clonal Rootstocks Through Mound Layering Under Shade Net Conditions

Apple clonal rootstock propagation through mound layering is commercially carried out in open-field conditions. However, the shade net conditions provide the congenial environmental conditions for better root formation and shoot growth. The preliminary study was conducted to elucidate the effect of different growing media (Cocopeat, Sawdust, Cocopeat + Sawdust [1:1], Soil) on rooting performance and growth of apple clonal rootstocks (M. 116, EMLA. 111, MM. 106) through mound layering under shade net conditions for 2 consecutive years (2021 and 2022). The growing media substantially impacted the different rooting metrics and growth of rooted stool shoots of apple clonal rootstocks. Results revealed that the clonal rootstocks exhibited a significant positive correlation with number of adventitious roots (r = 0.43), total root length (r = 0.44), length of rooted stool shoots (r = 0.42), fresh (r = 0.37) and dry weight (r = 0.38) of stool shoots, and plant biomass (r = 0.34), whereas a significant negative correlation with root:shoot ratio (r = −0.33). The combined application of growing media and rootstock M₃C₂ (Cocopeat + Sawdust [1:1] + EMLA 111) had a significantly higher number of adventitious roots per stool shoot (211.10), total root length (2.59 m), root diameter (2.11 mm), fresh weight (18.68 g) and dry weight (8.82 g) of roots, length (223.31 cm), diameter (11.58 mm), fresh weight (141.71 g), dry weight (79.01 g) and root:shoot ratio (0.16) of rooted stool shoots growth under mound layering in shade net conditions.