Xa33(t)

The Xa33(t) is one of Bacterial Blight(BB) resistance genes, having been identifyed from indica rice cultivar ‘Ba7’.

Annotated Information

Function Xa33(t) can confer resistance Xanthomonas oryzae pv. oryzae (Xoo). Bacterial blight (BB), a symptoms that lesions usually start near the leaf tips or leaf margins or both, and extend down the outer edge(s), caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive diseases in rice-producing areas in Thailand and it is especially prevalent in irrigated and rainfed lowland rice growing areas.BB disease can cause yield loss typically ranging from 20-30%, but in severely cases it can cause as high as 50% yield reduction. The utilisation of resistant varieties carrying resistance genes has been considered to be the most effective way to control the disease. Compare to Thai rice culticar 'TXO16' fully expanded leaves of each plant were inoculated, the leaves of 'Ba7' plants are measured few lesion length.And 'Ba7' with Xa33(t) confer resistance to many Thai Xoo isolates at both seedling and booting stages.

Expression Xa33(t) is a recessive gene with an incomplete dominance of susceptible allele in gene action, because the plants carrying heterozygous alleles (Xa33/xa33) exhibited an intermediate resistance in response to the Xoo pathogen.

Mapping This Xa33 resistance gene identified in rice ‘Ba7’ was located on the long arm of chromosome 6. In S. Korinsak1 and S. Sriprakhon1(2009) experiment, RM20590 was identified as the closest xa33(t)-linked marker.

Origin Amongst BB resistance genes identified on chromosome 6 including Xa7, Xa27 and xa32(t),Xa27 was reportedly located between RFLP markers RG424-RG162 (70.4-104.6 cM, Cornell map) on the long arm of chromosome 6, which is about 22.1 cM away from Xa7. It was originally found in wild rice O. minuta Acc 101141 [14] and introgressed into cultivated varieties.

References

Korinsak S, Sriprakhon S, Sirithanya P, et al. Identification of microsatellite markers (SSR) linked to a new bacterial blight resistance gene xa33 (t) in rice cultivar'Ba7'[J]. Maejo International Journal of Science and Technology, 2009, 3(2): 235-247.