Int.J.Curr.Microbiol.App.Sci (2017) 6(5): 2058-2066 2058 Original Research Article https://doi.org/10.20546/ijcmas.2017.605.229 Effect of Stem Rust Resistance Gene Sr2+ on Spot Blotch (Bipolaris sorokiniana) of Wheat and Triticale D.P. Singh* ICAR-Indian Institute of Wheat and Barley Research, 132 001, Karnal, Haryana, India *Corresponding author ABSTRACT Introduction The spot blotch caused by Bipolaris sorokiniana (Sacc.) Shoemaker in wheat and Triticale is a major disease problem in warmer and humid regions of India, Bangladesh and other South Asian countries. It causes losses up to 50% in grain yield and deteriorates seed quality. The host resistance is most effective and easily adopted way to manage the losses caused by this disease in grain and seed crop besides use of fungicides as pre sowing seed treatment and foliar sprays. Stem rust caused Puccinia graminis Pers.: Pers. f. sp. tritici Eriks. & E. Henn. is also one of the most devastating diseases affecting wheat yields globally. Sr2 is a stem rust resistance gene that has been used in breeding for around 60 years as a source of durable and broad-spectrum adult plant resistance, which includes resistance to Ug99 and its related isolates. Sr2 is located on the short arm of chromosome 3B and confers partial resistance only in the homozygous state (recessive resistance gene). It was originally transferred from Yaroslav emmer wheat into hexaploid wheat. Stem rust had been effectively managed using different resistant genes in International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 5 (2017) pp. 2058-2066 Journal homepage: http://www.ijcmas.com Spot blotch caused by Bipolaris sorokiniana is major disease problem in warm and humid areas of South Asian and other countries. Host resistance is an effective method to manage it and varieties with resistance to spot blotch and rusts are preferred. The stem rust resistant gene Sr2 along with other Sr genes is widely used in wheat and Triticale breeding programme to provide resistance against stem rust pathotypes including new Ug99 (TTKS). The presence of Sr2+ is also associated with morphological marker, pseudo black chaff (PBC) character, a dark pigmentation on the glumes, peduncle and below stem internodes of wheat. A total of 136 numbers of diverse genotypes of wheat and triticale having Sr2+ gene in sole and in combination with other Sr genes (Sr5+, Sr5+, Sr7b+, Sr8b+, Sr9b+, Sr9e+, Sr11+, Sr13+, Sr24+, Sr30+, Sr31+) were evaluated against spot blotch under artificially inoculated and epiphytotics at ten hot spot locations in northern plains agro ecological zones in India during 2000-01 to 2011-12 crop seasons. Based on scoring of spot blotch severity on top two leaves at mild milk stage, the genotypes were categorization of in to R, MR, MS and S category. A total of 69.9% of genotypes possessing Sr2+ genes were susceptible to spot blotch. Twenty genotypes possessing gene combinations of Sr2+5+, Sr2+5+24+, Sr2+5+3, Sr2+8b+11+, Sr2+9e+11+, and Sr2+24+ were all susceptible to spot blotch. The resistant and susceptible genotypes with Sr2+ gene were 30.1 and 69.9%, respectively. The results suggests that Sr2+ and other stem rust resistant genes may be used cautiously in varieties meant for warm and humid regions where spot blotch and leaf rust are major diseases. Keywords Stem rust, Resistant gene, Sr2+, Puccinia graminis f. sp. tritici, Spot blotch, Bipolaris sorokiniana, Wheat, Triticale Accepted: 19 April 2017 Available Online: 10 May 2017 Article Info