Potential of Botanicals for the Disinfection of Cowpea (Vigna unguiculata) Seeds and Bacterial Control in Burkina Faso

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Résumé

In Burkina Faso, diverse seed sources and weak phytosanitary control compromise seed quality and promote the spread of pathogens such us Xanthomonas genus strains. Strengthening local capacity in diagnostics and biocontrol is essential to enhance production system resilience. To this end, cowpea seed lots (Komcallé variety) were collected from six provinces of Burkina Faso. The bacterial load of the seed lots was evaluated on working samples of 1,050 seeds per province. The presence of bacteria of the genus Xanthomonas in these samples strains were genotyped using the X4c/X4e PCR primers. In addition, the efficacy of Ocimum gratissimum, Capsicum chinense, Zingiber officinale, Cassia nigricans and Piper nigrum extracts at a concentration of 4 g L-1 was evaluated in vitro on the bacterial load of cowpea seeds. In situ, germination rate and percentage
of leaf blight symptoms were used to compare the different treatments. The results showed that bacterial loads, expressed as log CFU mL-1, ranged from 7.585 to 8.185 depending on the origin. The PCR was positive for seven suspected strains. Among the treatments tested, Ocimum gratissimum and Capsicum chinense extracts (4 g L-1) significantly reduced residual bacterial load, with respective averages of 37 and 52 colonies, showing efficacy comparable to the bactericidal control IDEFIX (67 colonies). Under field conditions, O. gratissimum induced a high initial germination rate (83%) and reduced the incidence of bacterial blight symptoms (31%). Conversely, Zingiber officinale, Cassia nigricans and Piper nigrum promoted early germination but did not limit symptom progression.

Mots-clés

Bacterial; Burkina Faso; Capsicum chinense; Cowpea seed; Ocimum gratissimum