Alterations of Biochemical Composition of Leaf and Stem of Cowpea (Vigna unguiculata (L.) Walp.) by Colletotrichum destructivum O’Gara in Nigeria

Abstract

Colletotrichum destructivum during pathogenesis reduced the nutrient values of cowpea leaf and stem. The protein, fat, carbohydrate, fibre contents of the leaf decreased from 34.91%, 5.42%, 43.61% and 19.46% in the uninfected leaf samples to 20.40%, 2.15%, 37.03% and 15.53% in the infected leaf respectively whereas the moisture and ash contents increased by 10.88% and 11.15% in the uninfected leaf sample to 12.51% and 11.24% respectively in the infected leaf samples. The composition of zinc, sodium, magnesium, iron, and potassium in the leaf increased whereas calcium and phosphorous decreased after inoculation with the test fungus. It reduced the protein content from 15.64% in the healthy stem tissue to 12.69% in the infected one, fat from 1.29% to 0.78%, crude fibre from 16.87% to14.62%, and carbohydrate from 31.11% to 25.39%. Also, the fungus caused a reduction of the calcium and phosphorus contents of the healthy stem tissue from 2.09 mg and 326.50 mg to 1.19 mg and 299.10 mg respectively. Infection of the stem with the pathogen led to increasing moisture, potassium, sodium, zinc, iron, and magnesium contents from 11.80%, 230.12 mg, 111. 28 mg, 1.66 mg, 0.89 mg and 0.95 mg to 12.65% , 364.21 mg, 203.64 mg, 3.02, 1.52 mg, and 2.18 mg respectively. The average loss of the major nutrients; protein, fat, and carbohydrate was more in the leaf than stem, 34.29% and 18.14%  respectively 8 weeks after planting (WAP).