Field Efficacy of a Biopesticide Based on <i>Tithonia diversifolia</i>against Black Sigatoka Disease of Plantain (<i>Musa</i>spp., AAB)

Black Sigatoka disease (BSD) is a foliar disease caused by Mycosphaerella fijiensis, responsible of reduction of the photosynthetic area of banana plant and yield at harvest since it has an influence on fruit physiology. The control of BSD relies on the use of chemicals which are not affordable for the small holder farmers and increase the cost of production. Moreover, this chemical control is ineffective, negatively impacting the environment and human health, and is at the origin of strain resistance. Tithonia diversifolia is known as rich in many compounds such as mineral elements, defense metabolites, some phytochemicals;and it is increasingly used in agriculture. Recently, the protective effect of Tithonia diversifolia liquid extract against BSD development on plantain vivoplants in the nursery was highlighted. The aim of our study was to evaluate the efficacy of a biopesticide base on Tithonia diversifolia on the BSD development in a plantain field under high disease pressure. The effect of Tithonia diversifolia biopesticide on Mycosphaerella fijiensis mycelial growth in vitro was evaluated. An experimental field at the flowering stage was selected and treated with the biopesticide base on Tithonia diversifolia at three different concentrations: undiluted (100%), diluted at 1/2 (50%) and diluted at 1/4 (25%) for 17 weeks. The disease severity, the number of functional leaves, the youngest spotted leaf (YSL) and the youngest necrotic leaf (YNL) were evaluated in course of time. The biopesticide treatments significantly (P < 0.001) reduce the BSD severity in course of time, but it is more effective for the most diluted concentration (25%). The number of leaves increases in course of time as well as the rank of the YSL and the YNL confirming the efficiency of BSD control. The efficacy of this biopesticide base on Tithonia diversifolia could be a hopeful ecoresponsible solution for the plantain sector in general and in particular for poor small farmers.

Plantain Bananas PIF Seedlings Treatment with Liquid Extracts of <i>Tithonia diversifolia</i>Induces Resistance to Black Sigatoka Disease

Plantain bananas culture encounters the problems of seedlings quantity and quality unavailability. Black Sigatoka Disease (BSD) is one of the main pathological constraints of banana that can severely reduce the photosynthetic leaf area, leading to the losses of production of about 50% in banana plantation. The use of liquid extracts of Tithonia diversifolia could potentially induced the resistance of the PIF seedlings to BSD during the vegetative stages in the nursery. The aim of this work was to evaluate the effect of Tithonia diversifolia liquid extracts against the development of BSD on the PIF plantain bananas seedlings. The explants in the greenhouse and the seedlings in the shade were watered with liquid extracts of T. diversifolia during the process of PIF seedling production in sterile and non-sterile conditions. The treated seedlings show a more effective enhancement of seedlings quality parameters and also induce resistance against BSD. The vegetative stages parameters (the number of shoots, the diameter and the height of shoots, the foliar area, the length and weight roots) were improved in treated seedlings compared to controls ones. The treated seedlings showed maximum protection against BSD of up to 87% compared to controls. They also exhibited an increase in the accumulation of total proteins and total phenolics, as well as the activity of defense-related enzymes (peroxidase, polyphenol oxidase and glucanase). The treatment seems to acts as a vital stimulator and could therefore be a useful tool for small holder farmers favouring an eco-friendly agriculture using fewer synthetic inputs.

<i>Tithonia diversifolia</i>Mulch Stimulates the Growth of Plantain PIF Seedlings and Induces a Less Susceptibility to <i>Mycosphaerella fijiensis</i>in the Nursery

Plantain is an important crop that serves as a staple food and contributes significantly to income generation for millions of people in tropical and sub-Saharan Africa. Its cultivation faces the main constraint of seedlings unavailability in quantity and quality, essential for the creation of new plantations. The advent and popularization of the plantlets from stem bits (PIF) in the 2000s raised hopes for solving this problem. However, after about ten years, the PIF has shown some problems limiting its adoption and should be improved for more efficiency. The amendment of PIF substrate production with Tithonia diversifolia could be an alternative to seedlings’ unavailability. This study aims to evaluate the potential stimulative effect of T. diversifolia mulch on plantain PIF seedlings growth and protection against black Sigatoka disease (BSD)caused by Mycosphaerella fijiensis. The parameters of vegetative growth stages and biomarkers accumulation were assessed in sterilized substrate and non-sterilized substrate conditions. T. diversifolia mulch treatment increases the germination rate, the number of shoots, the height and the diameter of shoots, the leaf area as well as the seedlings roots, but it also protects the seedlings against BSD up to about 81% compared to the control seedlings. It also enhances the accumulation of biomarkers such as proteins, polyphenols content and defense-related enzymes (peroxidase, polyphenol oxidase and glucanase). T. diversifolia mulch seems to act in PIF seedlings production as a vital stimulator. It can therefore be taken as a tool for a more sustainable and resilient agriculture, and for poverty alleviation of poor small holder farmers.