Abstract
Climate change is expected to intensify water restriction to crops, impacting on the yield potential of crops such as popcorn. This work aimed to evaluate the performance of 10 field cultivated popcorn inbred lines during two growing seasons, under well-watered (WW) and water stressed (WS) (ψsoil≥ −1.5 MPa) conditions. Water stress was applied by withholding irrigation in the phenological phase of male pre-anthesis. Additionally, two contrasting inbred lines, P7 (superior line) and L75 (low performer) were compared for grain yield (GY) and expanded popcorn volume (EPV), selected from previous studies, were tested under greenhouse conditions. In the field, no genotype x water condition x crop season (G×WC×CS) interaction was observed, whereas GY (−51%), EPV (−55%) and leaf greenness (SPAD index) measured 17 days after anthesis (DAA) (> −10%) were highly affected by water limitation. In general, root traits (angles, number, and density) presented G×WC×CS interaction, which did not support their use as selection parameters. In relation to leaf senescence, for both WS and WW conditions, the superior inbred lines maintained a stay-green condition (higher SPAD index) until physiological maturity, but maximum SPAD index values were observed later in WW (48.7 by 14 DAA) than in WS (43.9 by 7 DAA). Under both water conditions, negative associations were observed between SPAD index values 15 and 8 days before anthesis DBA), and GY and EPV (r ≥ −0.69), as well as between SPAD index 7, 17, and 22 DAA, and angles of brace root (AB), number of crown roots (NC) and crown root density (CD), in WS (r ≥ −0.69), and AB and CD, in WW (r ≥ −0.70). Lower NC and CD values may allow further root deepening in WS conditions. Under WS P7 maintained higher net photosynthesis values, stomatal conductance, and transpiration, than L75. Additionally, L75 exhibited a lower (i.e., more negative) carbon isotope composition value than P7 under WS, confirming a lower stomatal aperture in L75. In summary, besides leaf greenness, traits related to leaf photosynthetic status, and stomatal conductance were shown to be good indicators of the agronomic performance of popcorn under water constraint.
Highlights
Since the pre-industrial period, anthropogenic activities mainly associated with increased greenhouse gas emissions, have caused an increase of about 1°C in the average global temperature
This study evaluated the use of possible players in the selection of contrasting grain yield (GY) and expanded popcorn volume (EPV) genotypes cultivated under greenhouse conditions
Plant Material This study evaluated ten popcorn inbred lines (S7), whose genealogy is derived from germplasm adapted to tropical (L61, L63, L65, and L71 from the BRS-Angela population) and temperate/tropical conditions (P7, from the commercial hybrid Zélia; P2 and P3, from the compound CMS-42; P6, from the commercial hybrid IAC-112; L54, L55, and L75 and L76, from the Barão de Viçosa population) (Kamphorst et al, 2019)
Summary
Since the pre-industrial period, anthropogenic activities mainly associated with increased greenhouse gas emissions, have caused an increase of about 1°C in the average global temperature. This increase may reach up to 1.5°C between 2030 and 2052, which tends to aggravate the frequency of extreme droughts and rainfall events worldwide (IPCC, 2019). This will have severe impacts on world agribusiness (Awange et al, 2016; Van Loon et al, 2016), for Brazil, whose economy relies on large-scale agricultural activities. The seed market offers cultivars with high-yield potential for environments with optimal water supply but, to date, there are no cultivars adapted to water deficit conditions, with droughts being one of the most limiting abiotic factors for the productivity of this crop (Kamphorst et al, 2019; Lima et al, 2019). It is essential to obtain genotypes which are more efficient regarding water use and identifying plant traits for genotypic selection under drought conditions
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