Abstract
LC-MS analysis of plant growth-promoting rhizobacterium (PGPR) Bacillus velezensis AP203 supernatants indicated the presence of nematode-inhibiting compounds that increased in abundance when B. velezensis AP203 was grown on orange peel. Meloidogyne incognita J2 were incubated with B. velezensis AP203 spores and orange peel, spores alone, orange peel alone, or with a non-inoculated control, and the combination of B. velezensis AP203 with orange peel resulted in 94% mortality of M. incognita juveniles (p ≤ 0.05). The J2 mortality rate for B. velezensis alone was 53%, compared to 59% mortality with orange peel, and the non-inoculated control exhibited 7% mortality. When tested on soybeans raised in a greenhouse, it was observed that when grown in the presence of orange peel, B. velezensis AP203 culture broth, cell suspension or supernatant reduced the numbers of M. incognita eggs per g of root at 45 days after planting (DAP) compared to inoculated controls in soybean and cotton (p ≤ 0.05). Likewise, soybean root length and fresh root weight significantly increased after inoculation with B. velezensis AP203 amended with orange peel. In cotton, shoot and root length significantly increased after inoculation with cell pellets of B. velezensis AP203 amended with orange peel compared to the M. incognita inoculated control. These data indicate that B. velezensis AP203 responds to growth on pectin-rich orange peel by production of biologically active secondary metabolites that can promote plant growth and inhibit root-knot nematode viability.
Highlights
Cotton (Gossypium hirsutum L.) and soybean (Glycine max L.) are economically important crops in the United States and worldwide
The mortality percentage of M. incognita J2 ranged from 0 to 100%, with 94% mortality observed for M. incognita eggs inoculated with the combination of B. velezensis strain AP203 with 1.0% (w/v) orange peel powder (OPP), which was significantly greater (p < 0.05) than that observed when eggs were incubated with B. velezensis AP203 alone (53%), 1.0% OPP (59%), or the negative control (7%) (Fig. 1)
Soybean root length of plants treated with culture broth from B. velezensis AP203 with OPP was significantly greater compared to the glucose treat ments and M. incognita positive control treatment (Table 1)
Summary
Cotton (Gossypium hirsutum L.) and soybean (Glycine max L.) are economically important crops in the United States and worldwide. In the U.S alone, cotton yield in 2018 was 18.4 million bales, and soybean yield was 4.54 billion bushels (Anonymous, 2018). Meloidogyne incognita (Kofoid and White) Chitwood, the southern root-knot nematode, is broadly distributed in soils cultivated with cotton (Xiang et al, 2017b) and other crops (Huang et al, 2016), and causes economically significant yield losses annually; for example, in 2018, soybean yield losses due to M. incognita in the southern U.S were estimated at 11.92 million bushels
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
