Fruit Quality and Polyphenolic Compounds of ‘Tupy' Blackberry Influenced by Pruning Time and Irrigation Management in a Subtropical Climate

In the southern states of Brazil, the largest blackberry cultivation area in the country, the harvest season for blackberries is November to February. In São Paulo state, the climate is warmer than the far south and harvest begins in October. Using management techniques such as pruning and growth regulators, it is possible to begin the harvest period earlier. Fruit marketed outside the normal harvest season returns higher prices to growers.  Our study examined berry weight and fruit quality impacts from winter pruning date and irrigation. The study was conducted at Fazenda Experimental São Manuel,  São Manuel-SP, Brazil. Three-year-old  ‘Tupy’ blackberries were trained to a 1.2 m high espalier-type trellis with four lateral canes retained in a “T” configuration. The experimental design was a 2 x 5 factoral, with two irrigation treatments (irrigated and non-irrigated) and five pruning-date treatments (pruning done on 5 May, 6 June, 7 July, 23 Aug., and 26 Sept.). There were four replications (six plants per replication. At the mid-point of the harvest period,  100 g of berries were collected from each replication and data recorded including average berry weight, titratable acidity, pH, soluble solids, and anthocyanin and total polyphenolic contents. There was an interaction between pruning date and irrigation treatment for berry weight and fruit quality variables. Berry weight ranged from 6.5 (pruned in May-non irrigated) to 9.7 g (pruned in August-irrigated). Soluble solids ranged from 9.5 (pruned in May-non irrigated) to 12.0% (pruned in August-irrigated), and  titratable acidity ranged from 0.66 (pruned in August-irrigated) to 1.44 mg/100g^-1fw of citric acid (pruned in June-non irrigated). The pH levels were different  only among  pruning dates,  ranging from 3.1 (pruned in May and June) to 3.6 (pruned in September). The highest concentrations of total polyphenols (258.7 mg of galic acid/100g^-1 fw) and anthocyanins (271.8 mg of cyanidin-3-glucoside/100g^-1 fw) were found with pruning performed in  May on non- irrigated plants. This was also a period when rainfall did not occur and temperatures were consistently lower than later in the harvest season.  Our study showed that date of pruning had a substantial influence on quality of ‘Tupy’ blackberry and this could impact acceptance by fresh-market consumers.