Quality of melons in relation to different qualities of irrigation water

Abstract

This research work was conducted in order to determine the effect of different water types on the quality of melons. Three varieties were considered for this experiment; Brimos, Ericino and Makdimon. The latter variety was grafted in order to determine the effects of grafting on fruit quality. The experiment was planned out in such a way that minimal environmental effects are experienced on the varieties, and therefore any differences would depend mainly on the water quality and genetic influences. Two water types were used mainly perched aquifer water (termed Spiera, sp) and sea water level aquifer (termed borehole, bh). Several morphometric parameters were studied mainly plant height, fruit dimensions, fruit weight and phytochemical constitution, mainly tint ratio, colour index, % Red, % Yellow, % Blue, anthocyanin content (mg/kg) and flavonoid content and polyphenols. There were interesting findings from this experiment. Although Ericino exhibited the highest fruit weight with both water treatments (>1979 g), the expected weight of mature fruit should be 2500 to 4000g. On the other hand, both grafted and non-grafted Makdimon exhibited high weights (1459-2225g) when compared to the suggested size range (1000-1500g). With respect to fruit lengths, Ericino exhibited larger lengths (>175mm) than for the Brimos and Makdimon. The melon varieties showed minimal width differences except for the grafted and non-grafted Makdimon melons especially with the borehole treatment. In order to compare growth trends between the varieties, the time was taken as days from transplanting. The Brimos and Ericino varieties exhibited a similar trend on plant height till maturity, while the non-grafted Makdimon exhibited different growth rates as compared to the grafted Makdimon. Physicochemical testing showed differences between varieties. The colour index was lowest for Ericino (0.123A) and highest for the grafted Makdimon (2.118A). Ericino exhibited a superior yellow colour for the bh water treatment rather than the more pronounced orange colour for the sp water treated melons. This goes in accordance with the tint ratio, being the highest with Ericino-bh treatment (15.89), while the lowest with Makdimon-sp treatment (1.534). The mean anthocyanin content was 2.80 mg/kg of melon fruit. This ranged from 0.16 mg/kg (Ericino-bh treatment) to 13.94 mg/kg (grafted Makdimon bh-treatment). The total polyphenolic content ranged between 0.0193 and 0.02330 %w/w, with the sp-water treated varieties showing values slightly higher than those treated with bh water. Principal component analysis on the morphometric analysis and polyphenolic content revealed that Ericino, Brimos and grafted Makdimon resulted in the varietal clustering, while the non-grafted Makdimon did not show consistent results. In conclusion, Ericino showed the best quality parameters although the maximum potential has not yet been achieved.