Gas Exchange and Transpiration Ratio in Sorghum

Abstract

Decreased water availability and increased food demand worldwide require development of more water‐efficient crops. This study was conducted to examine preflower transpiration ratio (CO2 assimilation rate [A]/transpiration rate [E], A:E) in four inbred sorghum [Sorghum bicolor (L.) Moench] lines and 12 of their F1 hybrids in terms of phenotypic and genetic variation, inheritance (i.e., additive and nonadditive genetic effects), and its relationship to water use efficiency (WUE) (i.e., the ratio of whole‐plant biomass to cumulative transpiration). Lines were selected with contrasting A and A:E in a field trial and then crossed in a full diallel pattern. All hybrids and lines were further analyzed for A, E, A:E, biomass, and WUE in a greenhouse. Variation among hybrids and lines was significant for all traits evaluated. In both environments, the most contrasting lines for A:E were Tx430 and Tx7078. Average A:E was 3.10 mmol CO2 mol−1 H2O for Tx430 and 2.91 for Tx7078. Both Tx430 and Tx7078 had highest A. Genetic effects resulting from general (GCA) and specific combining ability (SCA) for A, E, and A:E were significant for all traits. Tx430 had positive and Tx7078 negative GCA effects on A:E. Tx430 hybrids had the highest A:E values, and Tx7078 hybrids the lowest. The A:E ratio was correlated with total biomass and WUE for all crosses. Data suggest that concomitant selection for high A:E and A at preflowering could result in improved WUE and biomass of mature sorghum.

Stay-green quantitative trait loci's effects on water extraction, transpiration efficiency and seed yield depend on recipient parent background

“…Other reports also show the existence of genotypic variation in TE under differing water regimes (Donatelli et al, 1992;Balota et al, 2008) in a work that included Tx7078, a genotype with low TE and assumed to be tolerant to pre-flowering drought (Tuinstra et al, 1998). However, little prior assessment of TE in sorghum stay-green materials has been made and none of the previous reports show an evaluation of TE until maturity, except and Balota et al (2008). showed higher TE in one line having B35 as its source of stay-green.…”

“…In addition, the interaction of TE with water regime has been only tested in a few entries (Donatelli et al, 1992;Balota et al, 2008).…”

“…Conversely, it is difficult to obtain reliable yield data from plants grown in pots, especially because of the limited soil volume and planting density issues, although it has been done recently on a small set of hybrids (Balota et al, 2008). In our study, a lysimetric system is used to assess T, TE and HI in the same plants (Vadez et al, 2008).…”

Role of leaf photosynthesis and stomatal conductance in determining the genotypic variation in whole-plant Transpiration Efficiency (TE) in Sorghum

“…On the other hand, under severe drought stress, continual or severe restrictions in stomatal conductance severely implicates TE because of severe constraints on gas exchange that limits CO2 uptake, compromising photosynthesis and impeding further plant growth (Hammer et al, 2001;Monneveux and Ribaut, 2006a). Our data largely support the previous reports of increased TE under moderate levels of drought in sorghum and other crops.In addition, the absence of significant Genotype × Treatment (G×T) interactions for TE observed in our experiments was consistent with results reported by (Balota et al, 2008;Mortlock and Hammer, 1999), and may partly be due to the relatively low degrees of freedom in both of our experiments. However, it is important to note that genotype rankings were consistent across experiments (Tables 4.2 and 4.3), whereby, in Exp2, B923296, B963676 and R931945-2-2 consistently had the highest TE, while Tx7000, QL12, and NIL2219-3 had the lowest TE.…”

“…Sorghum is particularly recognised for its ability to be productive in water-limited situations due to its adaptation to arid environments (Burke et al, 2015). However, under severe water stress, particularly during growth stages most critical to yield formation, sorghum growth and yields can decrease (Balota et al, 2008). Under global climate change, both climate variability and the severity of climate events such as droughts are predicted to increase, which will put more pressure on dryland crop production, especially in the semi-arid regions (IPCC, 2014).…”