Water deficit and impaired pegging effects on peanut seed yield: links with water and photosynthetically active radiation use efficiencies

Abstract

Peanut (Arachis hypogaea L.) production is frequently affected by unpredictable events of water deficit during pod set, which modulate water use, water use efficiency for biomass production (WUEB), and biomass partitioning to seeds. We studied the effects of drought-induced impaired pegging on WUEB and the link between WUEB and photosynthetically active radiation use efficiency (PAR-UE). Field experiments were conducted that combined: two cultivars of contrasting pegging capacity (ASEM > Florman), two water regimes (irrigated and water stress) and different sowing dates. WUEB ranged between 6.1 and 6.7 g kPa/mm for irrigated plots, and between 2.9 and 7.1 g kPa/mm for water-stressed plots. WUE for pod production showed similar trends, but was larger for ASEM than for Florman because of higher biomass allocation to pods and pegging capacity of the former. The relationship between standardised values of WUEB and PAR-UE varied linearly for the post-R6 period, but fitted models differed between water regimes. This difference was attributed to the relative importance of stomata control on gas exchange (direct effects of water deficit) respect to feedback effects on photosynthesis caused by reproductive sink size (indirect effects of water deficit). Variation in post-R6 PAR-UE could be linked exclusively to the latter, but variation registered in WUEB acknowledged both controls.

Peg viability and pod set in peanut: Response to impaired pegging and water deficit

“…Interestingly, genotypic differences were detected in the general pattern of decline in peg viability. A permanent delay was observed for Cv ASEM as compared to Cv Florman, which may be linked to the enhanced biomass partitioning to reproductive structures registered for the former in previous studies (Haro et al, 2008(Haro et al, , 2010. These attributes, together with a more synchronous flowering pattern, may be responsible of the improved seed number and grain yield registered for Cv ASEM grown under water deficit (Haro et al, 2010).…”

“…A total of 480 pots were distributed at a distance of 50 cm among them. Pots were filled with soil of the type found in the peanut growing region of Argentina (Typic Haplustoll), for which water retention curves and the relationship between soil water availability and soil strength were described in previous papers (Haro et al, 2008(Haro et al, , 2010. Pots were kept free of weeds by manual weeding.…”

“…When water deficit takes place during pegging, reductions in seed yield are mostly linked to decreased pod set, and to a less extent to decreased seed weight Haro et al, 2008;Ono et al, 1974;Pallas et al, 1979;Skelton and Shear, 1971;Wright, 1989). This response is due to the direct effects of water deficit on plant growth (Haro et al, 2010) but also to indirect effects linked to topmost soil strength on pegging (Underwood et al, 1971). Lack of rainfall during this stage promotes increased surface soil strength, which impairs pegging and represents an additional factor limiting pod set and final seed numbers (Haro et al, 2008).…”

“…Similarly, no research documented the histological changes experienced by this reproductive structure. Moreover, studies on the negative effects of surface soil desiccation on pegging (Collino et al, 2001;Underwood et al, 1971), and related physiological responses (Haro et al, 2008(Haro et al, , 2010 did not analyze alterations in peg viability, which may vary widely among crops exposed to contrasting levels of deep soil water content that modifies plant water status. Genotypic variation in final pod number among peanut crops exposed to drought and surface soil desiccation Wright, 1989) may be also related to differences in peg viability, a trait that deserves attention for breeding crops adapted to the occurrence of water deficit events during pegging.…”

Peanut (Arachis hypogaea L.): A Prospective Legume Crop to Offer Multiple Health Benefits Under Changing Climate

“…Drought mediated increase in top soil hardness can restrict or delay peg penetration into the soil and therefore restrict the pegging stage resulting in limited pod set and subsequent seed numbers (Haro, Dardanelli, Otegui, & Collino, , ). However, in contrast, if the drought affected pegs are re‐watered, viable pegs starts penetrating the soil again (Haro et al., ).…”