Population dynamics of endophytic bacteria in field-grown sweet corn and cotton

Abstract

Investigations were designed to gain fundamental information on the microbial ecology of endophytic bacteria in model dicotyledonous and monocotyledonous hosts. Population dynamics of indigenous endophytic bacteria in cotton (Gossypium hirsutum L. 'DES119') and sweet corn (Zea mays L. 'Silver Queen') stems and roots were studied in a 2-year field trial by quantifying culturable bacteria at intervals during the season on three media: R2A, medium SC, and tryptic soy agar. Population dynamics of endophytic bacteria inside cotton petioles and bolls were also determined in 1 year. Endophytes were recovered from sweet corn roots and stems at seedling emergence at mean population densities of 4 log (colony-forming units per gram fresh weight (cfu/g-fw)) for both seasons, and were present throughout most of the growing season at populations ranging from 4 to 6 log(cfu/g-fw) in 1990 and 4 to 7 log(cfu/g-fw) in 1991. Endophytic bacteria were also present at emergence in cotton roots and stems in 1991 but were not detected until 2 days after emergence in 1990. Endophytic populations in cotton roots ranged from 4 to 6 log(cfu/g-fw) for most of the growing season in 1990 and 1991, while populations in cotton stems fluctuated between 3 and 7 log(cfu/g-fw) during both seasons. In cotton petioles, mean populations generally ranged from 1 to 4 log(cfu/g-fw), while no endophytic bacteria were recovered from bolls (minimum detectable limit = 1.30 log(cfu/g-fw)). The relative contribution of seeds and soil as sources of endophytic bacteria recovered from inside plants was assessed using surface-disinfested seed in a potting mix or on water-agar. With sweet corn, the mean endophytic bacterial population in seedlings grown on water agar was below 2 log(cfu/g-fw), while with cotton the mean was 5 log(cfu/g-fw) 6 days after germination. Internal populations resulting from surface-disinfested seed planted in nonsterile potting mix were 6 log(cfu/g-fw) at 6 days after planting with corn but only 2 log(cfu/g-fw) with cotton. These results indicate that endophytic bacteria are natural inhabitants of internal regions of roots and stems and that the endophytes may arise from both seeds and soils.Resume : Des recherches ont Ct C planifiCes pour obtenir des informations de base sur 1'Ccologie microbienne de bactkries endophytes chez des reprksentants modbles de monocotylCdones et de dicotyltdones. La dynamique des populations de bactkries endophytes indigbnes des racines et des tiges du cotonnier (Gossypium hirsutum L. 'DES119') et du mals sucrk (Zea mays L. 'Silver Queen') a Ct C CtudiCe durant 2 ans, dans des essais au chemp, par numkration B intervalles au cours des saisons des bactkries viables sur trois milieux de culture : le R2A, le milieu SC et la gClose tryptique de soya. La dynamique des populations des bactCries endophytes dans les petioles et les capsules du cotonnier a aussi Ct C CtudiCe au cours d'une saison. Des endophytes ont Bt C recouvrCes de racines et de tiges de mals sucrk, au stade de plantule en Cmergence, B des densitks ...

Response of endophytic bacterial communities in banana tissue culture plantlets to Fusarium wilt pathogen infection

“…Bacterial endophytes have been isolated from many different plant species, including tomato (Nejad and Johnson, 2000), potato (Garbeva et al, 2001;Sturz et al, 1999), wheat (Coombs and Franco, 2003;Germida et al, 1998;Siciliano et al, 1998), sweet corn (McInroy and Kloepper, 1995), cotton (McInroy and Kloepper, 1995), Vol. 54 LIAN,WANG,and ZHOU oilseed rape Nejad and Johnson, 2000), coffee (Fernando et al, 2005), sugarcane (James and Olivares, 1998) and citrus plants (Araujo et al, 2001(Araujo et al, , 2002.…”

A Bacterial Endophyte, Pseudomonas brassicacearum YC5480, Isolated from the Root of Artemisia sp. Producing Antifungal and Phytotoxic Compounds

“…After confirmation of the surface sterility of root segments, 1.0 g of dried plant root was ground in 9.0 ml of phosphate buffer (pH 7.2) with a sterile mortar and pestle. Serial dilutions were made using phosphate buffer and 100 µl of 10 3 -10 5 dilutions was applied on the 1/10 TSA plates and incubated at 28 o C for 3 days (McInroy and Kloepper, 1995). Among growing bacterial colonies, only bacterial strains having antifungal and/ or seed germination inhibitory activity were selected and maintained on 1/10 TSA at 4 o C for further experiments.…”

Identification and determination of characteristics of endophytes from rice plants and their role in biocontrol of bacterial blight caused by Xanthomonas oryzae pv. oryzae

“…The solution was diluted serially in the buff er and cultured on a TSA medium in a Petri dish. Single colonies were selected and purifi ed on fresh TSA plates (McInroy and Kloepper, 1995).…”