Crotalaria spectabilis and Raphanus sativus as Previous Crops Show Promise for the Control of Bacterial Wilt of Tomato Without Reducing Bacterial Populations

Abstract

Ralstonia solanacearum is responsible for bacterial wilt affecting many crops worldwide. The emergent population of R. solanacearum (phylotype IIB/ 4NPB) wilts previously resistant varieties and has rapidly spread throughout Martinique. No conventional method is known to control it. In this study, previous crops used as sanitizing crops were investigated as an environmentally safe alternative method of control. The ability of the emergent population of R. solanacearum to persist in planta and in the rhizosphere of Brassicaceae, Asteraceae and Fabaceae grown as previous crops was evaluated in controlled conditions, and the incidence of bacterial wilt was assessed in the following tomato crop. Results showed that all species carried R. solanacearum latently. Among Brassicaceae and Asteraceae, the highest density of R. solanacearum was found in planta and in the rhizosphere of Tagetes erecta. The density of the R. solanacearum population in the rhizosphere of Raphanus sativus cv. Karacter was significantly higher than that in Raphanus sativus cv. Melody. In Fabaceae, the density of R. solanacearum population in planta was statistically similar in all species. The density of the R. solanacearum population in the rhizosphere of Crotalaria juncea was significantly higher than that in Crotalaria spectabilis. This study showed for the first time that Crotalaria spectabilis and Raphanus sativus cv. Melody grown as previous crops improve the performance of the following tomato with similar effects on R. solanacearum populations in the soil as bare soil. The incidence of the disease in tomato decreased by 86% and 60%, after R. sativus cv. Melody and C. spectabilis, respectively, and the proportion of infected plants also decreased. These results suggest that C. spectabilis and R. sativus cv. Melody can be used as previous crops to help bacterial wilt control in ecological management strategies without drastic suppression of R. solanacearum population in stem tissues and in the rhizosphere.

Sample size for estimating mean and coefficient of variation in species of crotalarias

“…Bhandari et al (2016) highlight that the C. juncea is an important source of fiber, but that few studies have been developed, being the genetic breeding incipient in this species. C. spectabilis can reduce the incidence of Ralstonia solanacearum in tomato plants (Deberdt et al 2015) and also features low suitability for reproduction of Helicoverpa armigera (Reigada et al 2016). According to Machado et al (2007) and Braz et al (2016), C. spectabilis , C. breviflora and MARCOS TOEBE et al…”

Impacts of Temperature and Rootstocks on Tomato Grafting Success Rates

“…The environmental and human health impacts of chemicals used to control soilborne pathogens (e.g., methyl bromide, carbofuran, carbosulfan) have been raising concerns and have resulted in their gradually being phased out at various speeds depending on the countries involved. Efforts have been made to identify alternatives to pesticides, such as using plant extracts (Deberdt et al, 2012), applying compost (Noble and Coventry, 2005) or compost tea (Mengesha et al, 2017), intercropping (Deberdt et al, 2015), and soil solarization (Krueger and McSorley, 2009). However, such methods do not wipe out soilborne pathogens, but only reduce their pressure for a time in the first soil layers.…”

Tapping the potential of grafting to improve the performance of vegetable cropping systems in sub-Saharan Africa. A review

“…Interest in vegetable grafting has increased with the intensification of cropping systems, notably with the development of greenhouse cultivation in the 1950s and the phasing out of several chemicals used to control soilborne pathogens such as methyl bromide and carbosulfan. Although efforts have been made to identify different alternatives to chemicals, including the use of plant extracts (Deberdt et al 2012), intercropping (Deberdt et al 2015), use of compost or by-products of compost (Noble and Coventry 2010), and soil solarization, grafting is considered as one of the most effective ways to grow fruits and vegetables in soil containing soilborne pathogens. The advantages of grafting to improve yields of vegetables by increasing plant tolerance to abiotic stresses and their resistance to biotic stresses were discussed in several reviews (Rouphael et al 2017a;Keatinge et al 2014;Louws et al 2010).…”