Influence of Prunus rootstocks and spacing on performance of Japanese plum grown under sub–tropical conditions

Abstract

In India as well as in other significant regions of the world, plum production is focussed on a very small pool of varieties that inhibits its expansion and limits the availability of fruits all year round. This situation emphasizes on the urgent requirement of evolving alternative cultivars of rootstock and scion, with better performance under local situation and contrasting spacing. Japanese plum cultivar ‘Satluj Purple’ (Fla 1–2) is known for its hardy nature, precocity, high productivity and regularity in bearing appropriate for both the juice manufacturing industry and fresh fruit marketplace. In spite of having good fruit quality under sub–tropical scenario and early market availability when other fruits are not accessible, only a few rootstock studies for ‘Satluj Purple’ have been executed in India. Consequently, a field study was conducted at Punjab Agricultural University, Ludhiana state, to assess the horticultural output of ‘Satluj Purple’ Japanese plum grafted on four rootstocks: ‘Kala Amritsari’ (Prunus salicina L.), ‘Kabul Green Gage’ (Prunus salicina L.), Sharbati (Prunus persica Batsch) and Flordaguard (Prunus persica Batsch) over two consecutive seasons. The experimental grove was planted in 2015 using a 6 × 6 m and 6 × 1.5 m spacing, in a randomized block design, with three replications and two trees per replication under climate conditions typical of a semi–arid and sub–tropical area. Fruiting, yield and fruit quality were assessed for each rootstock at different spacing. Reproductive growth (fruit set, fruit retention and fruit yield per tree) was found to be higher on ‘Kala Amritsari’ rootstock. Fruits harvested from trees grafted on ‘Kala Amritsari’ were superior in fruit quality (fruit weight, fruit colour, total soluble solids (TSS), titratable acidity (TA) and ripening index (TSS/TA). Irrespective of the rootstocks, the performance of plum trees in terms of fruiting, yield and fruit quality was better in 6 × 6 m planted trees as compared to trees planted at 6 × 1.5 m distances. Yield was found to be positively correlated with fruit weight, chroma, TSS, ripening index, fruit set and retention while it was negatively correlated with the TA values. Overall, the results from this study indicated that the rootstocks ‘Kala Amritsari’ and ‘Kabul Green Gage’ are the most suitable rootstocks for ‘Satluj Purple’ under the conditions investigated herein. Finally, the ‘Satluj Purple’ trees at spacing of 6 × 6 m performed better as compared to 6 × 1.5 m planted trees regardless of the rootstocks.