Abstract
Beauveria bassiana strain 04/01-Tip, obtained from a larva of the opium poppy stem gall wasp Iraella luteipes (Hymenoptera; Cynipidae), endophytically colonizes opium poppy (Papaver somniferum L.) plants and protects them against this pest. The goal of this study was to monitor the dynamics of endophytic colonization of opium poppy by B. bassiana after the fungus was applied to the seed and to ascertain whether the fungus is transmitted vertically via seeds. Using a species-specific nested PCR protocol and DNA extracted from surface-sterilised leaf pieces or seeds of B. bassiana-inoculated opium poppy plants, the fungus was detected within the plant beginning at the growth stage of rosette building and them throughout the entire plant growth cycle (about 120–140 days after sowing). The fungus was also detected in seeds from 50% of the capsules sampled. Seeds that showed positive amplification for B. bassiana were planted in sterile soil and the endophyte was again detected in more than 42% of the plants sampled during all plant growth stages. Beauveria bassiana was transmitted to seeds in 25% of the plants from the second generation that formed a mature capsule. These results demonstrate for the first time the vertical transmission of an entomopathogenic fungus from endophytically colonised maternal plants. This information is crucial to better understand the ecological role of entomopathogenic fungi as plant endophytes and may allow development of a sustainable and cost effective strategy for I. luteipes management in P. somniferum.
Highlights
The symbiosis between plants and entomopathogenic Ascomycetes such as Beauveria bassiana (Bals.) Vuill., Isaria sp., Lecanicillium spp. (Ascomycota: Hypocreales) etc., has become an important area of study in crop protection, agronomy and ecology over recent years [1]
Our first objective was to ascertain whether B. bassiana strain EABb 04/01-Tip can effectively establish as an endophyte and colonize different opium poppy tissues at various stages of plant growth after spores were applied as a seed treatment
Using our PCR protocol and DNA extracted from surface-sterilised leaf pieces of B. bassiana seed-inoculated opium poppy plants, we detected the endophyte in 100% (8/8 plants), 87.5% (7/8 plants), 62.5% (5/8 plants) and 62.5% (5/8 plants) during the growth stages of rosette, early notching, end of notching, and capsule formation, respectively (Figure 1)
Summary
The symbiosis between plants and entomopathogenic Ascomycetes such as Beauveria bassiana (Bals.) Vuill., Isaria sp., Lecanicillium spp. (Ascomycota: Hypocreales) etc., has become an important area of study in crop protection, agronomy and ecology over recent years [1]. (Ascomycota: Hypocreales) etc., has become an important area of study in crop protection, agronomy and ecology over recent years [1] This interest has been triggered because endophytic behaviour is a newly discovered aspect of the life style of arthropod pathogenic fungi, and because entomopathogenic Ascomycetes symbioses can positively impact plant growth, resistance against invertebrate pests and fungal pathogens [1] [2] [3] [4]. We have described such an endophytic association between B. bassiana and opium poppy Papaver somniferum L., one of the oldest medicinal plants that is today the commercial source of important narcotic analgesics such as morphine [5] [6]. This molecular tool was used to demonstrate that B. bassiana strain EABb 04/01-Tip, when applied to leaves as a conidial suspension, effectively colonized aerial tissues of opium poppy plants mainly through intercellular spaces and even leaf trichomes [7]
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