Assessment of leaf spot disease on water leaf (Talinum triangulare (jacq.) Willd and in vitro effect of three medicinal plant extracts on pathogen(s) in the Northwest Region of Cameroon

Abstract

Cultivation of waterleaf improves the life quality of families and provides additional income for farmers. However, waterleaf production in Cameroon has suffered a major blow from leaf spot disease. Ten farms with dimensions of 4 m by 3 m each in Nkwen, Bamenda, Cameroon were surveyed for leaf spot disease of Talinum triangulare. Disease incidence and severity were assessed by surveying the farms after every fourteen days for three months. Small pieces of infected leaf parts were inoculated on prepared plates of potato dextrose agar. After 7 days of incubation, pure cultures were made, and isolated fungi were identified according to recommended references. Aqueous extracts from Moringa oleifera (Leaves), Ocimum gratissimum (Leaves) and Zingiber officinale (Rhizomes) were evaluated for in vitro antifungal activities on Alternaria and Cercospora. Data collected for disease incidence and severity showed varying intensities at the different locations. Two fungi species were isolated from the diseased leaf samples collected from 5 farms and were identified as Alternaria spp. and Cercospora spp. All the extracts had inhibitory activities on the test fungi with the highest inhibition (79.6%) obtained from Zingiber officinale (Rhizomes) extract and the lowest inhibition (4%) obtained from Ocimum gratissimum extract.

Cowpea (Vigna unguiculata (L.) Walp) Accessions Evaluation for Cercospora Leaf Spot Resistance Under Changing Weather

“…TVU-9099 had a relatively high yield, this result was rather absurd, but due to the fact that it was moderately susceptible to the CLS, the high yield observed could be attributed to the ability of the accessions to spread and maximize the rainfall and temperature for its yield, therefore, these accessions can be regarded as a high yielding accession 28 . This agreed with the report of Ahanger et al 26 , Timko and Singh 27 and Omoigui et al 28 and Anembom et al 29 that different reactions of cowpea genotypes to CLS were a result of genotypic differences. Generally, in this study the resistance to Cercospora leaf spot and yield of the accessions of cowpea were affected at a different rate on the accessions screened which attributes to the genetic makeup of the cowpea accessions.…”

“…The Cercospora leaf spot disease spread was favored by cool humid weather, high rainfall and moderate temperatures which must be favorable for combined initiation, development of plant disease during which it destroyed the foliage of the susceptible cowpea crops, the high rate of Cercospora leaf spot infection recorded in 2018 wet season was due to the high rainfall and high temperature recorded during the period of the experiment. The high temperature and moisture were favorable and combined for the initiation and development of plant disease which was consistent with the report 29,30 that high humid damp weather and high temperature favors the spread of Cercospora leaf spot disease. The high rate of Cercospora leaf spot incidence and severity was recorded in the wet season and no accessions were completely free of the disease.…”

“…This result supports the hypothesis that Cercospora leaf spot has marked effects on cowpea yield and disease development in cowpea plants. As corroborated by the findings 29 which reported that Cercospora canescens have a serious effect on yield under severe infestation up to 42% loss in yield.…”