Received: 17 July, 2011. Accepted: 10 August, 2011. Original Research Paper Fresh Produce ©2011 Global Science Books Effect of Natural Flooding and Postharvest Gibberellic Acid Application on Banana Fruits Alfonso Vargas 1* • Maricruz Ramírez-Sánchez 2 • Marco V. Sáenz 2 • Alvaro Segura 3 • Fabio A. Blanco 1 1 Corporación Bananera Nacional, P.O.Box. 390-7210, Guápiles, Costa Rica 2 Laboratorio de Tecnología Poscosecha, Universidad de Costa Rica, ZIP 2060, San Pedro, Costa Rica 3 Bayer S.A. P.O.Box 10018-1000, Heredia, Costa Rica Corresponding author: * alfvarga@corbana.co.cr ABSTRACT The effect of natural flooding for a period of 144 h was evaluated on banana fruit (Musa AAA, cv. ‘Grande Naine’) resulting from fruiting plants with physiological bunch age at the moment of the flood event of 10, 9, 8 and 7 weeks, from flooded (F) or non-flooded (NF) areas. Banana fruit of the F area were treated with GA 3 (0, 400, 800, 1200, 1600 mg kg -1 ) as a postharvest treatment. The variables measured were green and yellow life, pulp firmness (kg), soluble solids content (SSC; °Brix) and total titratable acidity (TTA; % of malic acid). A comparison of these variables between F and NF control areas determined the flooding effect. The effect of GA 3 evaluated only in the F area was determined by regression analysis. During the storage period of 21 days at 14°C (simulation transportation time) neither fruit from F nor NF areas showed any sign of natural ripening onset. The flooding event did not have any negative influence on the ripening process of the fruit. Flooding did not have any influence on firmness, SSC and TTA of harvested fruit. Independent of the GA 3 dose, the results showed an increment in SSC (19.04 to 23.17%) and TTA (0.31 to 0.42%) with an increase in the age of the fruit at the time of the flooding event. In general, different GA 3 rates applied to fruit from the F areas did not have an effect on the measured variables of yellow life, including the time to reach Grade 5 of maturity. These results suggest that the commercial practice of discarding bunches in the field after a flooding period may not be necessary in all cases. _____________________________________________________________________________________________________________ Keywords: Cavendish subgroup, flood, gibberellic acid, Grande Naine, green life, Musa AAA, yellow life Abbreviations: exp, experiment; F, flooded; GA 3 , gibberellic acid 3; NF, non-flooded; R-2, second ratoon INTRODUCTION Costa Rica exports approximately 104 million boxes of bananas of 18.45 kg each, from a planted banana area of 44,313 ha, with an income of USA $674 million (Jiménez et al. 2009). The largest planted area is located on the Caribbean side. This region is classified as Tropical Moist Forest and Tropical Moist Forest Premontane Transition (Holdrige 1967). The Caribbean zone has a high frequency of high inten- sity rainfall, with an annual average from 3,500 to 4,000 mm (Soto 2000). Some high rainfalls cause rivers to over- flow, especially those rivers with meandering courses. This, in connection with a flat topography of the area, induces serious flooding which affects the banana plantations situ- ated in this region. The decrease of soil oxygen levels caused by water excess, stops root growth, causes the roots to die, reduces plant photosynthesis and respiration rates, thus increasing the synthesis of foliar ethylene as a response to the stress condition. Symptoms of these alterations are primarily in the form of leaf chlorosis and wilting and the extent of damage depends on soil oxygen level (hypoxia, anoxia) reduction. Damage can vary from plant stunting and collapse, including the bunch (irreversible damage), up to loss in yield from reduced fruit dimensions or even the risk of fruit ripening during transport (Standard Fruit Co. 1975; Stover and Simmonds 1987; Soto 2000). Bananas may tolerate 72 h of flooding with flowing water, and 24 to 28 h under stagnant water or static flood water (Robinson 1992). Damage from flooding is more severe when water is standing than flowing (Israeli and Lahav 2000) which may be related with the lower oxygen content of standing water. Damage from flooding is more intense when high solar radiation occurs after the event (Sastry 1988). In plants flooded for 48 h growth ceases and first yellowing symptoms become apparent on leaves at this time, longer periods of flooding (72 to 92 h) result in irreversible damage (Israeli and Lahav 2000). The flooding effect is classified as light - when plants are exposed for 12 h or less; moderate - when they are exposed from 12 to 24 h; or severe - when exposure is for more than 24 h (Soto et al. 2008). In Central American banana plantations, the prac- tice is that after 48 h of flooding all bunches from affected areas are discarded in the field. Postharvest applications of gibberellic acid 3 (GA 3 ) delay fruit ripening (McDonald et al. 1997). The most cons- picuous effect is in the maintenance of fruit green color due to a delay in chlorophyll degradation (Khader 1991; McDonald et al. 1997; Zilkah et al. 1997). On bananas (Musa AAA), GA 3 induces vegetative elongation, abscis- sion of floral parts, delay in fruit senescence and an increase in fruit size (Vendrell 1970; Lockard 1975; Mishra et al. 1981; Lahav and Gottereich 1984; Satyanarayama 1985; Shanmugavelu et al. 1992; Kumar and Reddy 1998). The possibility of using GA 3 to delay ripening may help to postpone banana bunch harvest, and thus increasing dry matter accumulation. Also, as a postharvest treatment, there is evidence that AG 3 may affect the activity of starch deg- rading enzymes and therefore delaying the starch to sucrose conversion (Rossetto et al. 2003; Rossetto et al. 2004) al- though did not delay ethylene and CO 2 burst. This should happen also in fruits coming from bunches of plants stressed by biotic or abiotic factors like flooding. This ap- proach can contribute to increase yield. The objective of the present work was to evaluate the effect of natural flooding and postharvest application of GA 3 on banana fruit green and yellow life and quality. ®