Pathophysiological studies on sugar beet plants infected with Alternaria alternata, the causal agent of Alternaria leaf spot

Abstract

In vitro and in vivo experiments have been conducted to investigate the effect of the acetone extract of Capsicum annuum (ACA) and the fungicide Eminent (EMT) on Alternaria leaf spot (ALS) disease of sugar beet in Egypt. In vitro, the ACA was more effective than the fungicide, EMT as to its effect on linear growth inhibition of Alternaria alternate measured by IC50 (the concentration inhibiting 50% of linear fungal growth). Sixteen bioactive phytochemical compounds were identified in ACA by Gas chromatography and mass spectroscopy (GC-MS) analysis as follows: pentadecanoic acid, 14- methyl and methyl ester followed by n- Hexadecanoic acid, 1-(+) Ascorbic acid 2.6-dihexadecanoate, 6.9- Octadecadienoic acid, methyl ether, 10- Octadecenoic acid, methyl ester, Ethanol, 2-(9, 12- octadecadienyloxy)-, (Z, Z), 9, 12- octadecadienoic acid (Z, Z), 17- Octadecynoic acid, Oleic Acid, Cis- vaccenic acid, 2- myristynoyl pantetheine, Adipic acid, di(oct-4-yl ester), Di isooctyl adipate, alpha- Naphthyl red 1- Naphthalenamine, 4(phenylazo), Di -n- octyl phthalate 1,2- Benzenedicarboxylic acid, dioctyl ester and capsaicin. Identification of phytochemical compounds is based on the peak area, retention time of molecular weight, and molecular formula. In vivo experiments, the efficacy % of ACA treatment in reducing ALS was higher than treatment of EMT. Both treatments led to an increase in the total yield, sucrose %, and white sugar.