Effects of in vitro Drought Stress on Growth, Proline Accumulation and Antioxidant Defense in Sugarcane

Drought is the most limiting environmental factor to crop productivity and presents a great variability in the degree of tolerance among and within species, among varieties. The aim of this study was to characterize sugarcane accessions regarding tolerance to water stress during in vitro cultivation based on changes in biometric, physiological and biochemical characteristics, within species and among species, to support future breeding programs. Adventitious shoots of five sugarcane accessions: Saccharum robustum, Saccharum spontaneum and Saccharum officinarum species, cultivated in Murashige and Skoog medium supplemented with 2% sucrose and 4 g/l Phytagel were used in five water potentials, 0, -0.3, -0.6, -0.9, -1.2 MPa, induced by mannitol. Survival, length of shoots and roots, number of shoots and roots, biomass, proline content in leaves and activity of antioxidant enzymes were analyzed. There is difference among species, and also, within the same sugarcane species when submitted to in vitro drought stress, and S. officinarum was shown to be the most tolerant. Proline can be used as a biochemical indicator of response to drought in sugarcane accessions and its accumulation was intensified in S. robustum and S. spontaneum accessions. Catalase activity remained unchanged with increased drought in sugarcane accessions evaluated.

Genetic maps of Saccharum officinarum L. and Saccharum robustum Brandes & Jew. ex grassl

Genetic analysis was performed in a population composed of 100 F1 individuals derived from a cross between a cultivated sugarcane (S. officinarum `LA Purple') and its proposed progenitor species (S. robustum `Mol 5829'). Various types (arbitrarily primed-PCR, RFLPs, and AFLPs) of single-dose DNA markers (SDMs) were used to construct genetic linkage maps for both species. The LA Purple map was composed of 341 SDMs, spanning 74 linkage groups and 1,881 cM, while the Mol 5829 map contained 301 SDMs, spanning 65 linkage groups and 1,189 cM. Transmission genetics in these two species showed incomplete polysomy based on the detection of 15% of SDMs linked in repulsion in LA Purple and 13% of these in Mol 5829. Because of this incomplete polysomy, multiple-dose markers could not be mapped for lack of a genetic model for their segregation. Due to inclusion of RFLP anchor probes, conserved in related species, the resulting maps will serve as useful tools for breeding, ecology, evolution, and molecular biology studies within the Andropogoneae.