ISOLAMENTO E CARACTERIZAÇÃO DE BACTÉRIAS SOLUBILIZADORAS DE FOSFATO DA RIZOSFERA DE Eucalyptus sp.1

RESUMO A inoculação de micro-organismos solubilizadores de fosfato, em conjunto ou não com fungos micorrízicos, pode ser alternativa para a redução dos custos de produção de eucalipto por meio da diminuição dos gastos com fertilizantes fosfatados. Dessa forma, objetivou-se com este trabalho isolar e caracterizar bactérias solubilizadoras de fosfato da rizosfera de Eucalyptussp., visando à sua coinoculação com fungos ectomicorrízicos. Entre os 24 isolados de bactérias originários do solo rizosférico de eucalipto, 12 são do filo γ-Proteobacteria e pertencentes à família Enterobacteriaceae (Enterobacter, Kluyvera e Klebsiella); 9 do filo β-Proteobacteria (Burkholderia); 1 do filo Actinobacteria (Curtobacterium); e 1 do filo Firmicutes (Enterococcus). O índice de solubilização de fosfato, calculado dividindo-se o diâmetro do halo de clareamento pelo diâmetro da colônia, variou de 0 a 11, sendo Enterococcus avium a espécie com o maior potencial de solubilização de CaHPO4in vitro. A produção de acidez em meio glicose-extrato de levedura pelos isolados bacterianos rizosféricos foi significativa, no entanto a capacidade de solubilização de CaHPO4 não se correlacionou com a acidificação do meio. Alguns isolados bacterianos promoveram forte inibição do crescimento de Pisolithus sp., isolado H4111, enquanto outros não causaram esse fenômeno. Os isolados RE 56 (Enterococcus avium), RE 41 (Burkholderia cepacea), RE 52 e RE 30 (ambos Burkholderia pyrrocinia) foram aqueles que apresentaram maior potencial para utilização em experimentos de coinoculação com fungos ectomicorrízicos

Effects of low dose gamma irradiation of long period storage tomato seeds on germination percentage and seedling growth

Abstract Low dose gamma irradiation was used to study stimulation effects on germination percentage and seedling growth of long period storage tomato seeds. Irradiation dose of Co-60 source ranging from 0 (control), 20, 40, 60, 80 and 100 Gy were used to irradiated 2 yearsstorage tomato seeds. After irradiation, the seeds were planted in tissue paper. On the eight days of germination, germination percentage, seedling length and root length were measured. The result shows that the germination parameters of the tomato seedssignificantly increased when irradiated with 20 Gy of gamma rays. This study may be useful for stimulating the germination percentage of tomato seeds stored for a long period.</jats:p

Antifungal Activity of Plant Growth Promoting Rhizobacteria Against Fusarium oxysporum and Phoma sp. of Cucurbitaceae

Cucurbitaceae is the largest group of summer vegetables which includes about 118 genera and 825 species and most of which are known to possess medicinal values. Several major pathogens are known to infect cucurbits and cause yield loss up to 70–80 %. Among them, Fusarium wilt and black rot are prevalent in and around Mysore, Karnataka, India. Plant growth promoting bacteria (PGPR) in the rhizosphere, enhances plant growth by exerting their beneficial effects through metabolites that directly or indirectly influence the plant growth. In the present study, seven bacterial isolates were isolated from the rhizosphere soils of Cucurbitaceae crops near Mysore, India. The bacterial isolates were identified based on the morphological and biochemical tests. The root rot pathogen Fusarium oxysporum and black rot causing Phoma sp. were isolated from Cucurbitaceae crops. The antifungal activity of PGPR isolates against F. oxysporum and Phoma sp. was studied by dual culture assay. All the isolates were screened for their plant growth promoting traits such as phosphate solubilisation and ability to produce—indole acetic acid (IAA), siderophore, hydrogen cyanide (HCN) and enzymes. The PGPR strains showing more than two traits also showed good antifungal activity against F. oxysporum and Phoma sp. An increase in the growth rate accompanied by decreased disease intensity was noticed in the plants treated with selected PGPR