Abstract
DROUGHT is a major limitation to sustainable sugarcane production worldwide, and selection for improved drought tolerance can help sustain productivity while conserving water. Water deficit stress is known to alter a variety of physiological processes, which ultimately determine yield. Identifying suitable selection tools and drought tolerance traits would facilitate the crop improvement process. In this study, we evaluated the ability of three relatively rapid and nondestructive tools (namely, chlorophyll a fluorescence, CF, leaf chlorophyll content, CC, and leaf temperature, LT) to distinguish between sugarcane genotypes known to be either drought tolerant or susceptible, based on their yield performance under drought conditions in south Texas, U.S.A. Four susceptible, and four tolerant genotypes were grown in a field near Weslaco, S. Texas, and subjected to drought stress over a 90-day period and CF, CC and LT were measured three times during the treatment period. At 45 days after onset of treatments (DAT), CF (measured as the maximum photosystem II, PSII, photochemical efficiency), and leaf chlorophyll content (CC, measured with a Minolta SPAD meter) declined compared to values measured at 0 DAT. However, the reductions in CF and CC were only significant in leaves of drought-susceptible genotypes. Leaf temperature (measured with an infrared thermometer) increased in drought-stressed plants but the increase was significant only after 90 DAT and only in the drought-susceptible genotypes. The data indicate that either CF or CC can be used as rapid, nondestructive screening tools for drought tolerance among sugar genotypes. Introduction Drought is one of the most important environmental stress factors limiting sugarcane production worldwide. Development of drought-tolerant sugarcane germplasm is crucial for sustaining production in areas where water supply is limited. Water deficit stress is known to alter a variety of physiological processes such as radiation capture, leaf temperature, stomatal conductance, transpiration, electron transport, photosynthesis and respiration, which ultimately determine yield (Qing et al., 2001). Conversely, the ability to maintain physiological processes during moderate drought stress is indicative of the potential to sustain productivity under limited water conditions. Physiological traits of importance to drought tolerance seem to vary not only between species, but also among genotypes within a species and careful selection of suitable traits and methods of quantifying them is a necessary prerequisite for drought tolerance improvement. Although measurements of leaf photosynthetic rate may offer promise for characterising hybrid responses to drought stress, gas exchange techniques for assessing photosynthesis are laborious and not practical in crop improvement programs (Earl and Tollenaar, 1999). Previous
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Claims 5
Claim · model-written summary
At 45 days, chlorophyll fluorescence declined from day zero in sugarcane, significantly only in susceptible genotypes.
Verbatim
e0“At 45 days after onset of treatments (DAT), CF (measured as the maximum photosystem II, PSII, photochemical efficiency), and leaf chlorophyll content (CC, measured with a Minolta SPAD meter) declined compared to values measured at 0 DAT.”
e1“the reductions in CF and CC were only significant in leaves of drought-susceptible genotypes”
e2“subjected to drought stress over a 90-day period”
t0“sugarcane”
Claim · model-written summary
At 45 days, leaf chlorophyll content declined from day zero in sugarcane, significantly only in susceptible genotypes.
Verbatim
e0“leaf chlorophyll content (CC, measured with a Minolta SPAD meter) declined compared to values measured at 0 DAT”
e1“the reductions in CF and CC were only significant in leaves of drought-susceptible genotypes”
e2“subjected to drought stress over a 90-day period”
t0“sugarcane”
Claim · model-written summary
Drought raised sugarcane leaf temperature, significantly only after 90 days and in susceptible genotypes.
- Taxon
- sugarcanet0
- Treatment
- drought-stressede0
- Outcome
- Leaf temperaturee0
- Direction
- increasede0
- Qualifier
- only after 90 DAT and only in the drought-susceptible genotypese0
Not reportedComparator
Verbatim
e0“Leaf temperature (measured with an infrared thermometer) increased in drought-stressed plants but the increase was significant only after 90 DAT and only in the drought-susceptible genotypes”
t0“sugarcane”
Claim · model-written summary
The authors concluded that chlorophyll fluorescence can rapidly screen sugarcane genotypes for drought tolerance.
Not reportedComparatorValue
Verbatim
e0“either CF or CC can be used as rapid, nondestructive screening tools for drought tolerance among sugar genotypes”
e1“CF (measured as the maximum photosystem II, PSII, photochemical efficiency)”
t0“sugarcane”
Claim · model-written summary
The authors concluded that leaf chlorophyll content can rapidly screen sugarcane genotypes for drought tolerance.
Not reportedComparatorValue
Verbatim
e0“either CF or CC can be used as rapid, nondestructive screening tools for drought tolerance among sugar genotypes”
e1“leaf chlorophyll content, CC”
t0“sugarcane”
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