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The use of foliar applications of abscisic acid (ABA) to reduce blossom end rot (BER) in processing tomatoes

Smith, P. A., Argerich, C. A.
Acta horticulturae 2019 no.1233 pp. 7-12
Pyrus, Solanum lycopersicum, abscisic acid, biodegradability, canned vegetables, cultivars, evapotranspiration, foliar application, fruit set, fruits, mulches, pears, production costs, soil, soil quality, stomatal conductance, tomatoes, Argentina
Blossom end rot (BER) in susceptible cultivars can cause significant losses in the marketable production of processing tomatoes. When black biodegradable mulch is used, the cultivars of processing tomatoes that are susceptible to BER suffer an increase in the proportion of the affected fruits compared to bare soil conditions. Elongated Italian pear type cultivars of processing tomatoes that are used for premium whole peeled canned tomatoes are more susceptible to BER than blocky cultivars. The percentage of the fruits affected by BER increases by fivefold (2.7 vs. 14.5%) between a susceptible cultivar without, and with biodegradable mulch respectively. The objective of this study is to determine whether exogenous applications of ABA can reduce the incidence of BER in a susceptible cultivar. Trials were conducted in La Consulta, INTA Experimental Station in Mendoza, Argentina during the seasons 2014-2015, 2015-2016, and 2016-2017. Biodegradable black mulch 22 microns thick was used. Daily water replenishment was done by a single surface tape according to an evapotranspiration tank type “A”, adjusted by the local KC. A cultivar susceptible to BER was used: ‘HM 3861’ (HM CLAUSE). The experimental units were 5 m in length of soil bed with five replicates in a totally randomized complete design. During the main fruit setting period of the crop, four nocturnal foliar applications of ABA were used at five-day intervals. Four different concentrations of ABA were used: 0 (control), 100, 300, 500 mg L(-1) in season 2014-2015, 0 (control), 500, 1,000, 2,000 mg L(-1) in seasons 2015-2016 and 2016-2017. General production parameters including BER index, and stomatal conductance were measured. These parameters were evaluated by regression tests among treatments at α=0.05. The results obtained in the field showed no statistical differences in BER or any of the variables measured between treatments in the first season. In the second season stomatal conductance was lower with higher doses of ABA and the percentage of green fruit was higher. In the third season the highest concentration reduced BER, but at the cost of production. The results of the past two seasons indicate that the concentration at which ABA begins to reduce BER causes an unacceptable reduction in commercial yield, and is unviable for this purpose.