Bactérias endofíticas na produção de biomassa e potencial teórico de etanol do sorgo sacarino (Sorghum bicolor, L.) em condições de estresse salino

Abstract

The sweet sorghum is an alternative for the production of ethanol and biomass in areas that have water deficit, and/or salinity that restrict agricultural activity for showing tolerance to these abiotic stresses. Endophytic bacteria have been indicated as a factor of production in various cultures to confer nutritional, hormonal advantages, among others that result in promoting growth of plants (PGPB). Objective of this work is to evaluate the

potential of endophytic bacteria as a factor of production of sorghum under saline and non- saline conditions. An experimental model was established in the laboratory to select

cultivars of sorghum and sorghum PGPB with stress and without salt stress. Cultivars were selected from 13 genotypes (Sorghum bicolor: Rio, BR 501, BR 506, Roma, Ramada,

Tale, Theis, Willey, Wray, IPA 467-4-2, SF-15, IPA 8602502 and, S. sudanense: Sudan- 4202) cultured (30 d) in nutrient solution containing 8 and 75 mM NaCl. Three cultivars

were tolerant (IPA 8602502, Rio, Tale and BR 501) and two susceptible (Ramada and Wray). The Wray cv. was used for selecting PGPB (isolated from sugarcane). The IPACC8, IPACC9 (Herbaspirillum seropedicae) and IPACC12 (Azoarcus sp.) isolates were selected and evaluated with reference strains (BR11192 and BR11175). The three isolates attenuate the effect of salinity on water consumption of Wray. Without salt stress, some endophytes promoted biomass production in shoots (BR11192) or root (IPACC12 and IPACC8). The IPACC12 induced more hydrated plants. Endophytes were field tested with Wray and IPA 467-4-2 cultivars grown in saline and non saline soils. The fertilization with N (+N) or without N (-N) were controls. Juice production in +N, IPACC9 and IPACC12, promoted the highest theoretical ethanol (>14.9 m3 ∙ha-1 ) achieved in -N (9.7

m3 ∙ha-1 ) and, TEP promoted by IPACC12 was higher (1703 L∙ha-1

) than –N (908 L∙ha-1 ),

however, the TEP was intermediate in the other treatments (±1259 L∙ha-1

) in non-saline

soils. In saline soil, BR11175 showed higher biomass yield (28.8 Mg∙ha-1

) than –N (20.9

Mg∙ha-1 ), however, not differ to +N (±25.36 Mg∙ha-1

). Juice yields and TEP, treatments did

not differ (±9.03 m3 ∙ha-1 and ±830.2 L∙ha-1

). Adaptability analysis of PGPB effect over soil conditions showed stable effects on juice production and TEP. IPACC12 promotes the production of juice and TEP in sweet sorghum at least equivalent to N fertilization over soil condition.