Transpiration Response and Growth in Pearl Millet Parental Lines and Hybrids Bred for Contrasting Rainfall Environments

Abstract

Under conditions of high vapor pressure deficit (VPD) and soil drying, restricting transpiration is an important avenue to gain efficiency in water use. The question we raise in this article is whether breeding for agro-ecological environments that differ for the rainfall have selected for traits that control plant water use. These are measured in pearl millet materials bred for zones varying in rainfall (8 combinations of parent and F1-hybrids, 18 F1-hybrids and then 40 F1-hybrids). In all cases, we found an agro-ecological variation in the slope of the transpiration response to increasing VPD, and parental line variation in the transpiration response to soil drying within hybrids/parent combinations. The hybrids adapted to lower rainfall had higher transpiration response curves than those from the highest rainfall zones, but showed no variation in how transpiration responded to soil drying. The genotypes bred for lower rainfall zones showed lower leaf area, dry matter, thicker leaves, root development, and exudation, than the ones bred for high rainfall zone when grown in the low VPD environment of the greenhouse, but there was no difference in their root length neither on the root/shoot index in these genotypes. By contrast, when grown under high VPD conditions outdoors, the lower rainfall hybrids had the highest leaf, tiller, and biomass development. Finally, under soil drying the genotypes from the lower rainfall accumulated less biomass than the ones from higher rainfall zone, and so did the parental lines compared to the hybrids. These differences in the transpiration response and growth clearly showed that breeding for different agro-ecological zones also bred for different genotype strategies in relation to traits related to plant water use.Highlights:• Variation in transpiration response reflected breeding for agro-ecological zones• Different growth strategies depended on the environmental conditions• Different ideotypes reflected rainfall levels in specific agro-ecological zones

The Plant-Transpiration Response to Vapor Pressure Deficit (VPD) in Durum Wheat Is Associated With Differential Yield Performance and Specific Expression of Genes Involved in Primary Metabolism and Water Transport

“…The following day the transpiration response to changes in VPD was performed by exposing the plants, organized in a complete randomized design, to controlled increments in VPD from 0.6 to 4.1 kPa, applied by changing both temperature and humidity every hour from 8 a.m. (19°C and 70% RH), after 80 min. of light adaptation, to 5 pm (38°C and 40% RH), and maintained at a constant PPFD of ~400 μmol m −2 s −1 during the entire experiment, as reported in previous studies (Gholipoor et al, 2013; Vadez et al, 2014; Medina et al, 2017). The RH and temperature were recorded by two external sensors (DO9847, Delta Ohm, Caselle di Selvazzano, Italy) placed inside the chamber.…”

Breeding Drought-Tolerant Pearl Millet Using Conventional and Genomic Approaches: Achievements and Prospects

“…The limited TR trait in pearl millet operates by hydraulic regulation and partial closure of stomata contributing to water conservation. Drought-adapted genotypes have lower transpiration rates at high atmospheric evaporative demand than terminal drought-sensitive lines ( Kholová et al, 2010a , b ; Medina et al, 2017 ; Tharanya et al, 2018 ; Choudhary et al, 2019 ). The genotypes contrasting for transpiration rate under elevated VPD condition was found to differ in their dependence on water channeling pathway mediated through aquaporins which play an important role in hydraulic regulation ( Tharanya et al, 2018 ).…”

“…Drought stress in the vegetative stage is of frequent occurrence and seriously affects pearl millet growth ( Kholová et al, 2010a ; Medina et al, 2017 ; Shivhare and Lata, 2017 ), tillering ability ( van Oosterom et al, 2003 , 2006 ), and flowering ( Bidinger et al, 1987a ; Mahalakshmi et al, 1987 ), which are important components of crop productivity. The high-tillering nature of pearl millet compensates for loss of panicles in the main shoot under intermittent drought provided that water is available at a later season.…”

“…During high VPD conditions, transpirational water loss is higher, and photosynthetic efficiency is low; in other words, plants spend a lot of water molecules in transpirational cooling with very minimum CO2 fixation ( Figure 3 ). Limited TR under increasing atmospheric VPD was identified as one of the water-saving mechanisms and genotypic variations were reported in pearl millet ( Kholová et al, 2010b ; Medina et al, 2017 ). The limited TR trait in pearl millet operates by hydraulic regulation and partial closure of stomata contributing to water conservation.…”

Genome‐wide miRNAs profiles of pearl millet under contrasting high vapor pressure deficit reveal their functional roles in drought stress adaptations

“…Root exudation rates play a crucial role in plant water transport pathways and substantial variation in root exudation rate have been found in crops like sorghum, pearl millet, and chickpea (Medina et al, 2017;Sivasakthi et al, 2020;Tharanya et al, 2018). It also suggested that drought-adapted genotypes have a lower root exudation rate than drought-sensitive genotypes.…”