Fungos micorrízicos arbusculares, bactérias diazotróficas e adubação fosfatada em mudas de mamoeiro

Abstract

RESUMO-Conduziu-se um experimento em casa de vegetação para avaliar o crescimento de mudas de mamoeiro inoculadas com fungos micorrízicos arbusculares (FMAs) e com bactérias diazotróficas, na ausência e presença de fósforo. O delineamento experimental foi o de blocos casualizados, em arranjo fatorial 4 x 3 x 2, sendo os tratamentos compostos por: espécies de fungos micorrízicos arbusculares Glomus clarum, Gigaspora margarita, o inóculo misto Glomus clarum + Gigaspora margarita e o controle sem FMAs; as bactérias diazotróficas Stenotrophomonas maltophilia e Azospirillum sp. e o controle sem bactéria diazotrófica; duas doses de fósforo no solo, 0 e 25 mg dm -3 , todos com quatro repetições. Aos 105 dias após a semeadura, as plantas foram coletadas e avaliadas quanto à altura, área foliar total, diâmetro do caule, matéria seca da parte aérea, da raiz e matéria seca total, porcentagem de colonização micorrízica e contagem de bactérias diazotróficas nas raízes. As inoculações com os FMAs proporcionam aumentos significativos no crescimento das mudas de mamoeiro, mesmo em condições de baixa disponibilidade de fósforo, independentemente da presença de bactéria diazotrófica. O fungo G. margarita e o inóculo misto G. margarita + G. clarum destacam-se como os mais promissores para a cultura do mamoeiro. A inoculação com bactérias diazotróficas, na ausência ou na presença de FMAs, não propiciou efeito estimulatório ou supressivo no crescimento das mudas de mamoeiro. Termos para indexação: Carica papaya L., Gigaspora margarita, Glomus clarum, Stenotrophomonas maltophilia, Azospirillum sp. ARBUSCULAR MYCORRIHIZAL FUNGI, DIAZOTROPHIC BACTERIA AND PHOSPHATE FERTILIZATION ON PAPAYA SEEDLINGSABSTRACT -An experiment was carried out in a greenhouse to evaluate the growth of papaya seedlings inoculated with arbuscular mycorrhizal fungi (AMF) and diazotrophic bacteria, in the absence and presence of phosphorus. The experimental design was randomized blocks in a 4 x 3 x 2 factorial scheme, treatments consisting of: species of mycorrhizal fungi Glomus clarum, Gigaspora margarita and mixed inoculum Glomus clarum + Gigaspora margarita and a control without AMF; diazotrophic bacteria Stenotrophomonas maltophilia and Azospirillum sp., and a control without diazotrophic bacteria, and two levels of phosphorus in the soil, 0 and 25 mg dm -3 with four replications. At 105 days after sowing, the plants were collected and evaluated for plant height, leaf area, stem diameter, dry matter of shoot, root and total dry matter, percentage of root colonization and enumeration of diazotrophs in roots. Inoculation with AMF provides significant increases in the growth of papaya seedlings, even under low phosphorus availability, regardless of the presence of diazotrophic bacteria. The fungus G. margarita and the mixed inoculum G. margarita + G. clarum stand out as the most promising to the cultivation of papaya. The inoculation with diazotrophic bacteria in the absence or presence of AMF did not provide suppressive or stimulatory effect on papaya growth.

Growth and nutrient accumulation in mycorrhized papaya seedlings cultivated in a phosphorus-fertilized substrate

“…Inoculation with E. colombiana, G. margarita and S. heterogama promoted a 32, 33 and 36% increase in shoot dry matter, respectively, in relation to the control treatment, but did not differ among the fungal species (Table 3). Lima at al. (2011) reported that papaya seedlings inoculated with mycorrhizal fungi exhibited higher growth rates than those not inoculated, regardless of the amount of phosphorus in the soil.…”

“…(2001a) demonstrated that papaya cultivars can benefit from inoculation with Glomus clarum and G. margarita, reducing up to seven times the need for P fertilization so that maximum shoot growth can be achieved. Lima at al. (2011), evaluating growth of papaya cv Golden seedlings, showed that fungal inoculation treatments promoted an increase in seedling leaf area, with an increment of 19.3% in relation to the control treatment, which influenced dry matter accumulation but did not differ among the fungal species studied.…”

“…2008), potassium and phosphorus uptake (OLIVEIRA & OLIVEIRA 2005), tolerance to root diseases (BORGES at al. 2007), and improved seedling growth and vigor during its formation period (LIMA at al. 2011), can be jeopardized under field conditions.…”

Arbuscular mycorrhizal fungi and phosphate fertilization on star fruit tree seedlings

“…An alternative to the preparation of these seedlings is to use AMFs, which have contributed to reduce the production time of several fruit trees such as citrus (Altoé et al, 2008), yellow passion fruit (Cavalcante et al, 2001;Cavalcante et al, 2002), sweet passion fruit (Anjos et al, 2005;Vitorazi et al, 2012), papaya (Lima et al, 2011) and cashew (Weber et al, 2004), in addition to reducing phosphate fertilization (Riter Netto et al, 2014).…”

Brassinosteroide e fungo micorrízico arbuscular na produção do porta-enxerto tangerineira ‘Cleópatra’

“…Os fungos micorrízicos arbusculares, por sua vez, também têm proporcionado efeitos positivos no crescimento de plantas (Lima et al, 2011;Coelho et al, 2012), além do aumento da absorção de nutrientes, como o fósforo (Santos et al, 2011a) e o nitrogênio (Santos et al, 2011b). Assim, a utilização desses insumos pode promover um crescimento maior das mudas e, consequentemente, reduzir a fase de viveiro.…”