Vertical Distribution of Pasteuria penetrans Parasitizing Meloidogyne incognita on Pittosporum tobira in Florida

Abstract

Pasteuria penetrans is considered as the primary agent responsible for soil suppressiveness to root-knot nematodes widely distributed in many agricultural fields. A preliminary survey on a Pittosporum tobira field where the grower had experienced a continuous decline in productivity caused by Meloidogyne incognita showed that the nematode was infected with Pasteuria penetrans. For effective control of the nematode, the bacterium and the host must coexist in the same root zone. The vertical distribution of Pasteuria penetrans and its relationship with the nematode host in the soil was investigated to identify (i) the vertical distribution of P. penetrans endospores in an irrigated P. tobira field and (ii) the relationship among P. penetrans endospore density, M. incognita J2 population density, and host plant root distribution over time. Soil bioassays revealed that endospore density was greater in the upper 18 cm of the top soil compared with the underlying depths. A correlation analysis showed that the endospore density was positively related to the J2 population density and host plant root distribution. Thus, the vertical distribution of P. penetrans was largely dependent on its nematode host which in turn was determined by the distribution of the host plant roots. The Pasteuria was predominant mostly in the upper layers of the soil where their nematode host and the plant host roots are abundant, a factor which may be a critical consideration when using P. penetrans as a nematode biological control agent.

Chemical compounds from Dictyostelium discoideum repel a plant-parasitic nematode and can protect roots

“…incognita is a subterranean microbe that infects plants through the extended region behind the root tips. RKNs are widely distributed vertically, and some are distributed to a depth of 35 cm [ 20 , 21 ]. On the other hand, cellular slime molds are distributed on the surface layer of the soil, and it has been reported that fruiting bodies do not form below 1.5 cm from the soil surface [ 22 ].…”

Characterization of Nematicidal Activity and Nematode-Toxic Metabolites of a Soilborne Brevundimonas bullata Isolate

“…These bacteria include Bacillus subtilis [11], Bacillus thuringiensis [12,13], Bacillus amyloliquefaciens [14], Bacillus cereus [15], Bacillus firmus [16][17][18], Bacillus nematocida [19], Pseudomonas aeruginosa [20][21][22], Pseudomonas putida [23], Pseudomonas simiae [24], Pseudomonas syringae [25][26][27], Burkholderia cepacia [28], Streptomyces avermitilis [29,30], and Pasteuria penetrans [31]. These nematicidal bacteria affect the target nematodes through different mechanisms, such as restraining the growth and reproduction of nematodes and direct pathogenesis, which are carried out by the production of toxic proteins [32,33], enzymes [12,26,34], small-molecule metabolites [23,24,35], or invasive parasitization [36,37]. In this respect, bacterial nematicides have shown particular usefulness in terms of their relatively high specificity, their ability to act on the underground parts of plants, and the difficulty in resistance-development in nematodes.…”

Temporal expression patterns of Pasteuria spp. sporulation genes

“…Utilization of Pasteuria spp. as a biological control against plant-parasitic nematodes is a promising supplement to conventional methods (Luc et al, 2010;Schmidt et al, 2010;Kokalis-Burelle, 2015;Baidoo et al, 2017). Microscopic observations have been used to describe the development of P. penetrans inside the body of its host nematode (Phani and Rao, 2018), but more accurate methods with higher throughput are, in the current study, transcripts of Spo0F, and the Sigma factors Sigma-F and Sigma-G are used as landmarks to track the development of P. penetrans, inside their respective nematode hosts.…”