Abstract
This study was designed to characterize morphological, physiological and molecular responses of sugarcane genotypes to a simulated water deficit stress. Two genotypes (TSP05-4: Drought-tolerant; TCP02-4589: Drought-sensitive) were subjected to a 20-day water deficit treatment and an 8-day recovery period. Leaf photosynthesis (Pn), transpiration rate (E), stomatal conductance (Gs), leaf greenness index (SPAD) and variable-to-maximum chlorophyll a fluorescence ratio (Fv/Fm), were evaluated before, during and after water deficit. Root-to-shoot ratio (R/S), stalk height (SH), diameter (SD) and stalk weight (SW) were evaluated at the end of the experiment. Real-time RT-PCR confirmed seven differentially-expressed transcript-derived fragments (TDFs) identified by cDNA-AFLP. Pn rates were similar between the genotypes under well-watered conditions. However, under water deficit, TSP05-4 had higher Pn rates. SPAD, Fv/Fm and R/S were also generally higher in TSP05-4, regardless of soil moisture status. Water deficit-induced reductions in SH and SW were greater in TCP02-4589 than in TSP05-4. Three TDFs showing sequence similarities to genes encoding a putative expressed pentatricopeptide, a protein kinase CK2 regulatory subunit CK2β3, and a glucose-6-phosphate/phosphate translocator 2 were identified in TCP02-4589. One TDF similar to a drought-inducible protein was identified in TSP05-4. Recovery of physiological processes and gene expression patterns to the water stress levels was fast. Key words: Differential gene expression, water deficit stress, re-watering, Saccharum spp.
Highlights
Sugarcane (Saccharum sp.) is an economically important crop that is cultivated in more than 90 countries for sugar, ethanol and biomass production
Two sugarcane genotypes classified as either drought tolerant (TSP05-4) or sensitive (TCP02-4589) were used
Plants of each genotype were randomly divided into one group subjected to a water deficit stress regime by maintaining volumetric soil moisture (VSM) at ~15%, and another group being well-watered (VSM ~ 35%)
Summary
Sugarcane (Saccharum sp.) is an economically important crop that is cultivated in more than 90 countries for sugar, ethanol and biomass production. The period between 60 and 150 days of crop age, known as the formative phase, has been shown to be very sensitive to water deficit stress in sugarcane (Naidu, 1976). Water deficit during this phase has been shown to adversely affect gene and protein expression, morphological, physiological and biochemical traits, and cane and sugar yields (Rocha et al, 2007; Silva et al, 2008; Cha-um and Kirdmanee, 2009; Rodrigues et al, 2009). Plasticity in adjusting to and recovering from drought is often overlooked in drought response studies, even though these mechanisms can enhance crop survival during water shortages (Ashton, 1956; Inman-Bamber, 1995). A better understanding of these responses and mechanisms is necessary in developing guidelines and procedures to efficiently screen germplasm for stress tolerance
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