Biological and chemical induction of resistance to the Globodera tabacum solanacearum in oriental and flue-cured tobacco (Nicotiana tabacum L.).

The effects of acibenzolar-S-methyl (ASM) and four combinations of plant growth-promoting rhizobacteria (PGPR) on the reproduction of a tobacco cyst nematode, Globodera tabacum solanacearum, and growth of Nicotiana tabacum (cv. K326 and Xanthi) were tested under greenhouse and field conditions. The PGPR included combinations of Bacillus subtilis A13 with B. pumilis INR7, B. pumilis SE34, B. licheniformis IN937b, or B. amyloliquefaciens IN937a, respectively. Among the four rhizobacterial combinations, IN937a + A13 exhibited the most consistent reduction in G. t. solanacearum cysts under greenhouse and field conditions. No undesirable effects of IN937a + A13 were observed on tobacco growth under greenhouse and field conditions. Use of INR7 + A13 reduced G. t. solanacearum reproduction on flue-cured tobacco cv. K326 but not on oriental tobacco cv. Xanthi. Application of ASM reduced final numbers of G. t. solanacearum cysts, but also resulted in phytotoxicity mainly under the greenhouse conditions. When oriental tobacco seedlings were pre-grown in a IN937a + A13-treated soil-less medium, a single application of ASM at 200 mg/L one week after transplanting significantly reduced G. t. solanacearum reproduction in the field.

Effects of Ph gene-associated versus induced resistance to tobacco cyst nematode in flue-cured tobacco.

Effects of the systemic acquired resistance (SAR)-inducing compound acibenzolar-S-methyl (ASM) and the plant-growth promoting rhizobacterial mixture Bacillus subtilis A13 and B. amyloliquefaciens IN937a (GB99+GB122) were assessed on the reproduction of a tobacco cyst nematode (TCN- Globodera tabacum solanacearum) under greenhouse conditions. Two sets of two independent experiments were conducted, each involving soil or root sampling. Soil sample experiments included flue-cured tobacco cultivars with (Ph(p)+: NC71 and NC102) and without (Ph(p)-: K326 and K346) a gene (Ph(p)) suppressing TCN parasitism. Root sample experiments examined TCN root parasitism of NC71 and K326. Cultivars possessing the Ph(p) gene (Ph(p)+) were compared with Ph(p)- cultivars to assess the effects of resistance mediated via Ph(p) gene vs. induced resistance to TCN. GB99+GB122 consistently reduced nematode reproductive ratio on both Ph(p)+ and Ph(p)- cultivars, but similar effects of ASM across Ph(p)- cultivars were less consistent. In addition, ASM application resulted in leaf yellowing and reduced root weight. GB99+GB122 consistently reduced nematode development in roots of both Ph(p)+ and Ph(p)- cultivars, while similar effects of ASM were frequently less consistent. The results of this study indicate that GB99+GB122 consistently reduced TCN reproduction in all flue-cured tobacco cultivars tested, while the effects of ASM were only consistent in Ph(p)+ cultivars. Under most circumstances, GB99+GB122 suppressed nematode reproduction more consistently than ASM compared to the untreated control.