[Submergence tolerance and Sub1 locus in rice].

Great progresses have been made in understanding of both submergence tolerance in rice (Oryza sativa L.) and the molecular mechanism of tolerance over 4 years. Tolerance of rice plants to submergence is controlled by Submergence-1 (Sub1) locus. Sub1 regulates ethylene- and GA-mediated responsiveness, leading to restriction in carbohydrate consumption and quiescence in shoot elongation during submergence and subsequently causing submergence tolerance. This article reviewed two strategies adopted by rice plants to cope with flooding stress, major physiological factors affecting submergence tolerance, and physical mapping of Sub1 locus, as well as the mechanisms of submergence tolerance, and assessed the prospects of the use of Sub1 in hybrid rice production.

[Cytogenetic maps and their applications in plants].

Integrated cytogenetic maps encompass the information from both genetic maps and cytological maps. It is possible for cytogenetic maps to simultaneously report the cytological and genetic position of a maker. To constructure cytogenetic maps it is necessary to relate the markers mapped across linkage groups to cytological position on chromosomes. Cytogenetic maps have been constructured primarily in two ways. The first general strategy is to utilize the chromosome breakpoints to determine the location of genetically mapped markers on the chromosomes. A second way is by the direct hybridization of genetically mapped sequences onto chromosomes by FISH. In addition, a novel approach is to use RN-cM maps to predict the physical position of genetic markers on the chromosomes. Cytogenetic maps suggest that both the density of genes and the frequency of recombination increase towards the distal regions of chromosome arms, and they play significant roles in revealing gene colinearity between two species, exploring the evolution relationship between both of them and in map-based gene isolation.