Ecophysiological and biochemical selection markers for tolerance to heat and water stress in soybean

ERGO, V.V.; LASCANO, R.H.; VEGA, C.R.C.; PAROLA, R.; CARRERA C.S

Florianopolis

Congreso; VII Congresso Brasileiro de Soja (VII CBSoja)- Mercosoja 2015; 2015

Embrapa Soja

ECOPHYSIOLOGICAL AND BIOCHEMICAL SELECTION MARKERS FOR TOLERANCE TO HEAT AND WATER STRESS IN SOYBEANERGO, V.V.1; LASCANO, R.H.2,3,4; VEGA, C.R.C.1; PAROLA, R.2; CARRERA C.S.2,3; 1INTA EEA Manfredi, Córdoba, Argentina, veronicaergo@gmail.com; 2IFRGV-CIAP-INTA; 3CONICET; 4FCEFyN-UNC. As a result of climate change, rising temperatures and modification of amounts and patterns distribution of rainfall can potentially impact on plant production and crop yield. There is ample evidence supporting that heat stress episodes (HS) and/or water stress (WS) during seed filling decrease yield mainly through decreases in seed weight (SW) and to a lesser extent in seed number (SN) (PRASAD et al., 2008). Multiple ecophysiological, biochemical, morphological and/or molecular alterations could underlie yield responses to abiotic stress. E.g. leaf total starch (LSt), protein (LPr) and total chlorophylls (TChl) decrease with HS and WS (ERGO et al., 2013); whereas total soluble sugars (LSS) increase under WS probably to maintain the osmotic adjustment in leaves (MANAVALAN et al., 2009). Maximum quantum efficiencies (Fv/Fm) and quantum yield of photosystem II (ᶲPSII) decrease due to deterioration of the photosynthetic apparatus (INAMULLAH & ISODA, 2005). Malondialdehyde (MDA, a widely used indicator of membrane damage by ROS) increases under stress conditions, while antioxidant compounds decrease (LIU et al., 2008).Although great effort has been made towards the understanding of the detrimental effect of abiotic stresses interaction on soybean production, approaches integrating different study scales, such as the ones combing ecophysiological and biochemical variables in field situations are still scarce. Therefore, the objective of this work was to analyze the assimilate source response to HS and/or WS during seed filling in soybean, and to find potential selection markers for genotypes screening. An experiment was conducted in INTA Manfredi (31º 49'S, 63º 46' W) during two crop seasons (2012-2014) using two soybean cultivars (SPS4x4 and SPS4x99). The experimental design was a split-split plot with 2 replications, resulting in a three factorial arrangement: water level, genotype, and temperature level. Water levels were: i) non water stress (NWS, near field capacity) achieved by drip irrigation, and ii) water stress (WS, near 20% of available soil water content) during 35 days from growth stage R5.5 (FEHR & CAVINESS, 1977). Temperature levels were: i) non heat stress (NHS, ambient temperature), and ii) heat stress (HS), comprising brief periods of exposure to temperature >32°C for 6 hours per day, during 21 days from R5.5. Recorded field variables were: ᶲPSII and Fv/Fm with a modulated pulse meter (Hansatech, FMS2 model), leaf chlorophyll meter (SPAD) with a chlorophyll meter (Minolta SPAD-502) and relative water content (RWC). Laboratory variables included measurements of ferric reducing ability of plasma (FRAP), MDA, TChl, LSS, LSt, LPr and total ureides (allantoic acid and allantoin). At harvest, yield (g m-2) and its components (SN, SW) were determined. ANOVA tests were performed at the 5% significance level (p