Abstract

Rice is the primary source of food for 57% of the world’s population. Genetic resistance is important to control many kinds of pathogenic diseases. Bacterial blight caused by Xanthomonas oryzae pv oryzae (Xoo) decreases rice production by 20 – 30% and up to about 90% loss of grain weight. xa5 is an important recessive bacterial blight resistant gene, which is effective and important in Asian rice breeding program. It was also used in combination by incorporation with various recessive and dominant BB resistant genes. The purpose of our study was to identify the bacterial blight resistant genes xa5 in Pakistani rice germplasm including Basmati varieties. The seeds were collected from different research institute and then sowed in the National Institute for Biotechnology and Genetic Engineering (NIBGE) in pots. DNAs were extracted and surveyed for polymorphism by using DNA marker linked to xa5 gene. During this polymorphic survey, out of 88 germplasm lines, 45 lines showed the presence of xa5 gene like MB 2, MB 33 MB 57 and MB 66. All these lines showed the amplification of 240 bp corresponding to resistant source IRBB-5 line, while 43 germplasm lines showed no such fragment and elucidated same bands as susceptible source IR-24 having fragment of about 230 base pair. The 10 Pakistani Basmati varieties were also surveyed for xa5 gene. It was observed that none of our cultivated basmati varieties exhibited the presence of xa5 gene. The purpose of screening of xa5 gene in Pakistani rice germplasm is to utilize the local source of xa5 gene for elite molecular breeding program being carried out at NIBGE in future including pyramiding of different disease resistant gene in Basmati varieties.

Key words: Rice, xa5, bacterial blight, linked marker.

Abbreviation

BLB, Bacterial leaf blight; CR, complete resistance; PR, partial resistance; LRR, leucine-rich repeat; NBS, nucleotide-binding site; RFLP,restriction fragment length polymorphism; BAC, bacterial artificial chromosome;PCR, polymerase chain reaction.