Genetic variation and association of molecular markers for iron toxicity tolerance in rice

Iron toxicity in rice field can cause abnormality in plant growth leading to yield loss of 35-45%. This is caused by microbial reduction under flooded conditions of insoluble iron-III (Fe 3+) into soluble iron-II (Fe2+). The severity and symptoms of Fe toxicity depends on the growth stage of rice plant at which it is exposed to the stress. The plant developed various mechanisms to avoid/tolerate such stress which is a complex phenomenon governed by multiple genes/QTLs. Very few chromosomal loci are reported for Fe toxicity resistance in rice. But no locus has been fine mapped or cloned yet. Association mapping provides opportunity to have a greater coverage of genetic diversity in various germplasm lines so that large number of loci can be identified for Fe toxicity in rice. In the present investigation, 71 genotypes including landraces and released varieties were screened for their Fe toxicity resistance ability. Various agro-morphologic traits were observed to be affected by Fe stress. The genotypes Dhusura, Jalapaya, Gelei, Kendrajhali, Rasapanjari, Saluagaja and Asinasita were observed to be
resistant under field stress condition and controlled condition in hydroponic culture. These genotypes can be used as donor lines for improvement of Fe tolerance in rice. The marker-trait association study could identify the markers namely RM243, RM234, RM248, RM501, RM594 and RM517 to be associated with leaf bronzing index which is considered to be indicator of Fe toxicity resistance. These markers individually showed phenotypic variance ranging from 6.0-10.5%. These markers can further be used for marker assisted breeding programs to incorporate the Fe resistance genes/QTLs into susceptible high yielding popular varieties.