Incidence of Leaf Blight Disease of Mulberry Plant and Assessment of Changes in Amino Acids and Photosynthetic Pigments of Infected Leaf

Healthy growth and development of silkworm is largely depending on the quality of mulberry leaves fed. Leaf blight is one of the common disease, which reduce the leaf yield and affects the rearing quality of the leaves. Leaf blight disease incidence of mulberry plant in different parts of Bangladesh was studied for three years. Disease incidence was studied by counting the healthy and infected leaves in three vigorous branches of each plant and disease severity was recorded according to grading method. The changes of amino acids and photosynthetic pigments in infected leaf were also performed by biochemical analysis. Results showed that the maximum leaf infection was found in Comilla and Rangamati which was 71.01 and 68.45%, respectively. The highest disease severity was recorded in Comilla (42.28%), Rangpur (38.87%) and Dinajpure (37.6%). Biochemical studies showed eight and five amino acids present in healthy and diseased leaves, respectively. Amino acid contents were always found to be higher in healthy mulberry leaves than infected ones with total absence of iso-leucine, glutamic acid and cystine. Serine, lysine, aspartic acid, leucine, glutamic acid, alanine and cystin were found in excess in healthy mulberry leaves. The drastic reduction of total chlorophyll, chlorophyll a, chlorophyll b and β-carotene in blight infected leaves and decreased by 53.24, 51.65, 56.53 and 58.04% were recorded. This study indicates that due to leaf blight infection and change in amino acids and chlorophyll a and b might be the cause of yield and quality reduction of mulberry leaves for silkworm production in Bangladesh.