TITLE:
Impact of Cluster Thinning on Quality of “Malbec” Grapes in Encruzilhada do Sul-RS
AUTHORS:
Maria Inez Lopes Fernandes de Barros, Dianini Brum Frölech, Letícia Leal de Mello, Roberta Manica-Berto, Marcelo Barbosa Malgarim, Vagner Brasil Costa, Paulo Mello-Farias
KEYWORDS:
Vitis vinifera, Maturation Index, Bioactive Compounds, Ravaz Index, Polyphenols
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.9 No.3,
February
27,
2018
ABSTRACT: The cultivar Malbec has been present’s good
performance and quality in the South Half of Rio Grande do Sul (RS). In this
context, we aimed to evaluate the quality of “Malbec” grapes in relation to the phytotechnical, physicochemical
parameters and bioactive compounds under different intensities of cluster
thinning in Encruzilhada do Sul-RS. The
experiment was carried out in a commercial vineyard in the 2015/16 with the
cultivar Malbec (Vitis
vinifera L.) under rootstock “1103 Paulsen”, with spacing of 2.2 m between rows and 1.1 m
between plants. The experimental design was of randomized complete blocks with
five replications. The treatment factor tested was the cluster thinning, with
four levels (0%, 10%, 30% and 50%), performed in véraison. The evaluated phytotechnical variables were cluster
length, cluster fresh weight, berries fresh weight, number of berries, rachis
fresh weight. Also what were determined are the number of clusters, production and Ravaz index. The physicochemical
variables verified were pH, soluble solids (SS), titratable acidity (TA) and
SS/TA ratio. The bioactive compounds were total polyphenols index and total anthocyanins.
The appropriate balance between source and sink, by the Ravaz index, occurs to zero and 10% of cluster thinning.
The “Malbec” grapes present an increase
of the maturation index (SS/TA) at 50% of cluster thinning, due to the low titratable
acidity at this level. The total polyphenols index has a larger increment when
the plants are submitted to the cluster thinning of 10%, providing a larger
quality to the fruits. At all the levels of cluster thinning tested, when
compared to the control, there was a greater contribution of total anthocyanins
in the berries.