Efficacy of Peroxidase Activity and Isozyme as Molecular Markers for Assessing Iron Deficiency and Toxicity Via in Vitro Culture as a Rapid Technique in Banana

Abstract

In arid and semi-arid zones, iron (Fe) deficiency represents great challenge for banana cultivations. There is no available standard table for fertilization program of banana in these areas. Therefore, the current study aimed to test the in vitro culture technique as a more rapid methodology for screening the appropriate Fe level and its relation to the activity and isozymes fingerprints for peroxidase in “Williams” banana plantlets. After the fourth subculture of multiplication, the experiments were started. The tested concentrations of Fe relative to Fe content in the Standard Murashige and Skoog medium (MS) were 0%, 100%, 200%, 300%, 400%, 500%, 1000% and 1500%. The analogous concentrations of Fe were 0, 5.50, 11.0, 16.5, 22.0, 27.5, 55.0 and 82.5 mg L^–1, respectively, which applied in a completely randomized design using ten replicates. The obtain results proved that removing Fe from MS caused Fe deficiency and the most common symptom was chlorosis of the entire lamina, then all plantlets turned yellow or white. On the contrary, the excess concentration in Fe (82.5 mg L^–1) in MS tended to blacken the shoots and arrested growth. Removing Fe from the medium gave the lowest value of peroxidase activity. Contrariwise, peroxidase activity was progressively increased by elevating concentration of Fe in the medium. The activity of peroxidase remained stable in plantlets grown in 11, 16.5 and 22 mg L^–1 Fe. Thereafter, a sharp increase in activity was observed in plantlets grown in 27.5 mg L^–1 Fe. This increase continued to reach the maximum in plantlets grown in the medium supported with the highest Fe concentration (55 mg L^–1). It could be concluded that there is a positive relationship between Fe concentration in MS-medium and peroxidase isozymes. This is useful in diagnosing iron deficiency or toxicity in laboratory, affording the opportunity to perform various tests to obtain rapid information that can be used in constructing an accurate fertilization program schedule for banana under field conditions.