Comparative responses of morphophysiology and nitrogen metabolism in the interaction between peanut cultivars with contrasting drought tolerance and Bradyrhizobium sp.

FURLAN, ANA LAURA; MORLA, FEDERICO; BIANUCCI, ELIANA; CASTRO, STELLA

Congreso; LVIII Reunión Anual SAIB; 2022

Legumes are environmentally important due its ability to fix atmospheric nitrogen into organic compounds through biological nitrogen fixation (BNF). They grow in temperate and warm climates, being susceptible to unpredictable episodes of water deficit. Drought stress constraints legume vegetative growth stages such as germination, growth, dry matter partitioning as well as reproductive stages such as tiller production, organ development, seed filing and seed quality. Therefore, this study aimed to evaluate morphophysiology, nitrogen metabolism and yield in the interaction between peanut cultivars with contrasting drought tolerance and the strain able to infect peanut plants Bradyrhizobium sp. For that, seeds of two peanut cultivars, Granoleico (sensitive) and EC-98 (tolerant), were inoculated with Bradyrhizobium sp. SEMIA6144 and 30 days after sowing, plants were separated into the experimental groups: control, drought stress (withholding irrigation until the apparition of wilting symptoms), and drought stress and subsequent rehydration (rewatering of plants subjected to drought stress). Root and nodule morphology were analyzed by light microscopy (histological preparations); N-compound contents (i.e. aminoacids, ureides and nitrates) were quantified spectrophotometrically; N and C contents in shoots were analyzed by inductively coupled mass spectrometry (ICP-MS) and, finally, crop yield was evaluated in two seasons (2016/17 and 2017/18). The results obtained on root anatomy and histology, although revealed differential responses between cultivars were not associated with tolerance traits in the tolerant cultivar (EC-98). However, nodules of EC-98 showed invariable diameter and infection zone upon the exposition to drought stress and rehydration compared to nodules of Granoleico plants exposed at the same treatments. The balance of C- and N-contents and N-compounds in EC-98, i.e., an invariable content of C in shoots and of nitrates and ureides in roots and nodules of stressed and rehydrated plants, an increase in total amino acids only in nodules of stressed plants and small reduction in shoot N-content (compared with the sensitive cultivar), were associated to an efficient BNF. This cultivar may be able to transport the N products from nodules to shoots in order to prevent the N-feedback limitation of BNF. These traits would contribute to greater yields in the peanut-Bradyrhizobium sp. interaction as observed in the dry season 2017/2018. Thus, the EC-98-Bradyrhizobium sp. interaction exhibits tolerance traits derived from the N-balance and nodule metabolism (as revealed by histology and physiology) which would contribute to yield during challenging seasons with drought stress episodes affecting the crops.