Modified BBCH codification and correlation of phenological characteristics with climatic variables in jamun (Syzigium cuminii Skeels)

Abstract

Jamun (Syzigium cuminii Skeels) is gradually gaining importance due to its extraordinary medicinal properties and enhanced demand for fresh fruit, which is buttressed by the growth of the processing industry. Curative property of Jamun fruits against Diabetes mellitus type 2 has boosted its commercial orcharding, which necessitates gathering precise information on phenological responses to changing temperature and precipitation. A modified three digit extended Biologische Bundesanstalt Bundessortenamt and Chemische Industrie (BBCH) scale was developed and assigned 3 digit codes to describe the important phenological stages. Eight principal growth stages and 36 secondary stages have been described with illustrations that occur sequentially in Jamun under subtropics. Interestingly the primary phenophases of vegetative phenology i.e. bud development, leaf development and shoot development showed a large overlap and the interrupted phenostages are attributed to the inclemental weather conditions. Thus, under a warm temperate subtropical climate in the northern hemisphere, Jamun canopies presented two vegetative flushes (represented as mesostage 1 and 2), the second flush registering highest frequency (60–80 %) in months of September to October. This is in contrast to continuous growth under tropical climate conditions, wherein growth cessation does not occur. While vegetative growth flush occurred twice a year in a major part of canopy, flower-bearing panicles emerged on mature shoots in the months of February and March. Floral induction characterized by the inflorescence emergence and subsequent blooming closely followed the upswing of average monthly minimum and maximum temperature curve under subtropics, while average temperature downturn coupled with high precipitation released the vegetative flush episode. The phenostage (5) involving inflorescence emergence and growth occurred once in the subtropical climate, sustaining for around 8 weeks, followed by flowering (6) and fruit development(7). As with other evergreen trees, vegetative growth did not depict cessation and dormancy was observed after harvest and onset of winter. The correlation of emerging phenological events with temperature and humidity established the utility of the BBCH code for forecasting the outcomes of the canopy shoots. Early fruit production and synchronous shoot growth can be targeted by imposing shoot pruning strategy immediately after harvest at dormancy. The study establishes interplay of ecogeography and germplasm for expression of standard phenostages and the impact of climate change on fruit productivity.