Calcium Nitrate Fertilizer Effect on Anthracnose Disease Caused by Colletotrichum Gloeosporioides penz. and Tuber Rot by Botryodiplodia Theobromae pat. in Dioscorea Alata Variety Alakisa

Otusanya MO*

Received: July 12, 2018;   Published: July 30, 2018

DOI: 10.26717/BJSTR.2018.07.001493

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Abstract

Three or more years fallow may not replenish enough for optimum quality of Dioscorea (food cultivars) tubers. This study indicated this because Calcium and Nitrogen of values 0.47cmol kg^-1 and 0.2% respectively were still below the critical determined for optimum yam production (South West Nigeria) even after three years fallow followed by two consecutive years of calcium nitrate fertilization to Dioscorea on the field plot used in this study. The experiment was a 3 by 3 factorial, arranged in RCBD and 3 replicates. Ca (NO₃)₂ soil amendment at 0, 1, 2kg ha^-1 of calcium was the main plot treatment applied at 3 MAP (months after planting) and one foliar spray only at the rates 0, 100 and 500mg l^-1 Ca (NO₃)₂ applied at 5 MAP. Ca (NO₃)₂ soil amendment (1 and 2kg ha^-1) and 100mg l^-1 Ca (NO₃)₂ foliar spray all promoted more leaf phytoanticipins namely flavonoid, lignin and tannin over the control. Leaf minerals namely N, P, Fe and S increased in the soil amendment treatments over the control and N, P and Fe in turn correlated significantly with the three phytoanticipins with their antimicrobial activities. The 2kg ha^-1 x 0mg l^-1, 0kg ha^-1 x 100mg l^-1 gave anthracnose severity score of 1 which is resistant level. The 1kg ha-1 x 500mg l^-1, 1kg ha^-1 x 100mg l^-1 both gave anthracnose severity score of 2 which is moderately susceptible. Only the highest fertilizer interaction of 2kg ha-1 x 500mg l^-1 gave susceptible severity score of 3.67. The remaining four interactions had the score of 3 (moderately susceptible). As Alakisa is an early susceptible variety the 3 MAP soil amendment plus monthly 100mg l^-1 Ca (NO₃)₂ is recommended in further trials to establish optimum interaction for anthracnose control. Infection of 1.03% and 0% weight loss in tubers incubated with B. theobromae for 2 weeks is lower than any report of infection and weight loss reduction of B. theobromae by calcium fertilizer. Yield of 18.24tons ha^-1 in this study is within the potential range of 16 to 25tons ha^-1 with the recommended 8 bags (400kg) of NPK 15-15-15 per hectare under continuous yam monocropping in Niger.

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