Plant Growth Promoting Rhizobacteria: A tool to complement plant peanut breeding programs.

BIGATTON ED; HARO R; ARCHILLA MV; FABIO E; LUCINI EI; PALMERO F; VÁZQUE C; BRUNO M ; MORENO V; AYOUB I; BERDINI A; DUBINI L ; MERLO C

Córdoba

Simposio; 1° Simposio de Mejoramiento Genético Vegetal; 2021

Introduction.Ensuring food security has become a crucial challenge for plant breeding programs (PBP) in the face of climate change events. Drought and heat stress will be the major problems to achieve high yields. An alternative to complement the benefits gained in the PBP are Plant Growth Promoting Rhizobacteria (PGPR). PGPR interacts with plant rhizosphere through direct and indirect effects stimulating plant growth under stressful conditions. PGPR could be used on many different crops, such as peanut (Arachis hypogaea L.). Peanut is one of the most important oilseeds sown in Argentina, especially in Cordoba, which concentrates more than 88% of the sowing area (350.000 ha). This crop is mainly affected by water restriction in different moments during their life cycle. Root growth enhancement is a valuable plant trait to overcome drought events during the early crop stages and set plants stand. Objective.Evaluate the effects on root growth of peanut seedlings treated with PGPR under water stress conditions. Materials and Methods.ASEM 400 INTA (ASEM) and GRANOLEICO (GRA) cultivars grew in pots without water restrictions from seeding to the emergence and, under water restrictions from emergence onwards. Four treatments were tested: (i) Bacillus sp. (RI3), (ii) Bacillus sp. (SC6), (iii) Pseudomonas sp. (PSE10), and (iv) control without PGPR application. Fifteen pots were used per treatment. Seeds were surface-sterilized and after inoculated to reach an apparent concentration of 9 x 109 CFU.seed-1 (i-iii treatment). An extra 80 µL. seed-1 of PGPR application was added to the bottom of the seed socket (3cm depth) to reach 8 x 106 PGPR.seed-1. The seedling grew to germination without water and soil limitations, after that, two water regimens per treatment were imposed [40% and 60% of field capacity (FC)]. Root biomass was determined to 15 days after emergence. Treatments effects were relativized to the control (iv) and a means comparison test was performed using Fisher´s LSD test (p< 0.05). Results.PGPR stimulated root growth concerning the Control treatment and its effects contrasted among treatments. There were variations between cultivars and water regimes (15% and 4%, respectively). Nevertheless, the effect of the application of PGPR was higher and statistically different. PGPR stimulated higher root growth when water restriction was higher (40% FC> root biomass> 60% FC). Root growth increased up to 20-120% (6-35% with respect to the same treatments at 60% FC) when seedlings were subjected to moderate stress (40% FC). This trend was similar in all treatments, except in PSE10 for cultivar ASEM (Figure 1). SC6 was the PGPR that induced closer responses between water regimes in both cultivars, suggesting higher stability. RI3 had the greatest contrast between growth conditions, increasing root production under water deficit by approximately 40%. That is a valuable attribute for the environment of Córdoba province.Conclusion.PGPR under water stress enhance the root growth of peanut plants and this attribute should be considered in PBP. Further studies with more severe water stress and variable analysis should be carried out to elucidate the effects.