POSSIBLE INTERACTIONS OF POLYAMINES AND ETHYLENE DURING RIPENING OF GUAVA (PSIDIUM GUAJAVA L.) FRUITS

Recent Advances in Novel Packaging Technologies for Shelf-Life Extension of Guava Fruits for Retaining Health Benefits for Longer Duration

Guava (Psidium guajava L.) fruit is also known as the apple of tropics, belongs to the family of genus Psidium, and is widely cultivated in tropical zones of the world. Recently, the importance of guava fruit has increased due to its inherent nutritional content, pleasant aroma, excellent flavor, and delicious taste. It is considered an excellent source of nutrients and phytochemicals. Guava is a climacteric fruit that continues to mature or ripen even after harvest, showing an increase in the rate of respiration and metabolic activities within a short period, leading to rapid senescence or spoilage of fruit. It has limitations in terms of commercialization due to short storage life after harvest and sensitivity to diseases and chilling injury during the storage period. Many postharvest technologies such as edible packaging, modified atmosphere packaging (MAP), composite packaging, controlled atmosphere packaging (CAP), antimicrobial/antifungal packaging, and nano packaging have been used to retard the chilling injury and enhance the keeping quality of guava fruits during the storage period to control respiration rate, reduce weight loss, minimize lipid oxidation, and maintain organoleptic properties. However, these packaging technologies have varied effects on the internal and external quality attributes of guava fruits. This review, therefore, discusses the physiology, mechanism of ripening, oxidation, and ethylene production of guava fruits. The review also discusses the packaging technologies and their effect on the postharvest characteristics of guava fruits during the storage period.

Functional characterization of 1-aminocyclopropane-1-carboxylic acid oxidase gene in Arabidopsis thaliana and its potential in providing flood tolerance

Ethylene is a phytohormone that has gained importance through its role in stress tolerance and fruit ripening. In our study we evaluated the functional potential of the enzyme involved in ethylene biosynthesis of plants called ACC (aminocyclopropane-1-carboxylic acid) oxidase which converts precursor ACC to ethylene. Studies on ethylene have proven that it is effective in improving the flood tolerance in plants. Thus our goal was to understand the potential of ACC oxidase gene overexpression in providing flood tolerance in transgenic plants. ACC oxidase gene was PCR amplified and inserted into the pBINmgfp5-er vector, under the control of a constitutive Cauliflower Mosaic Virus promoter. GV101 strain of Agrobacterium tumefaciens containing recombinant pBINmgfp5-er vector (referred herein as pBIN-ACC) was used for plant transformation by the 'floral dip' method. The transformants were identified through kanamycin selection and grown till T3 (third transgenic) generation. The flood tolerance was assessed by placing both control and transgenic plants on deep plastic trays filled with tap water that covered the soil surface. Our result shows that wild-type Arabidopsis could not survive more than 20 days under flooding while the transgenic lines survived 35 days, suggesting development of flood tolerance with overexpression of ACC oxidase. Further molecular studies should be done to elucidate the role and pathways of ACC oxidase and other phytohormones involved in the development of flood adaptation.

Bioactive amines in Passiflora are affected by species and fruit development

Bioactive amines were determined in selected passion fruit species and throughout fruit development. The same amines (spermine, spermidine, agmatine, putrescine and tryptamine) were found in four Passiflora species (2008-2010 growing seasons) at different concentrations: P. alata had higher polyamines (spermine+spermidine, 8.41mg/100g); P. setacea and P. nitida had higher putrescine (>7.0mg/100g); and P. setacea had higher agmatine contents (1.37mg/100g) compared to the others. The indolamine tryptamine was present at low concentrations in all species (~0.05mg/100g). P. nitida and P. alata had the highest soluble solids (~18°Brix); P. edulis had the lowest pH (2.97) and P. nitida the highest pH (4.19). Throughout P. setacea fruit development, the concentrations of spermidine, putrescine and agmatine decreased; spermine contents did not change; and pH decreased. Fruit shelf life and some of the health promoting properties of Passiflora and their synthesis are modulated by species.

Oxidative stress and antioxidant systems in Guava (Psidium guajava L.) fruits during ripening

Two varieties of guava viz., L-49 and Hisar Safeda differing in their shelf lives were analyzed for various components of oxidative stress and of enzymatic and non-enzymatic antioxidative system at different stages of fruit ripening. Indices of oxidative stress viz., lipoxygenase activity, malondialdehyde value and H2O2 content increased throughout during ripening in both the varieties. The extent of oxidative stress was more pronounced in Hisar Safeda (shelf life 3-4 days) than in L-49 (shelf life 7-8 days). Except for superoxide dismutase, activities of all other antioxidative enzymes viz., catalase, peroxidase, ascorbate peroxidase and glutathione reductase increased up to color turning stage and decreased thereafter. Superoxide dismutase activity, however, increased upto ripe stage followed by a decline. Contents of ascorbic acid and glutathione (total, oxidized and reduced) were found to be the maximum at turning and mature stage, respectively. It is inferred that ripening of guava fruit is accompanied by a progressive increase in oxidative/peroxidative stress which induces antioxidant system but not until later stages of ripening. Over-accumulation of ROS due to dysfunctioning of ROS scavenging system at later stages of fruit ripening appears to be responsible for loss of tissue structure as observed in ripened and over-ripened fruits.