Cereal Rusts and Powdery Mildews Bulletin

A.N. Mishra¹, A.P. Roelfs² and H.J. Dubin³

¹ Indian Agricultural Research Institute, Regional Wheat Research Station, Indore 452 001, India

²Cereal Rust Laboratory (now Cereal Disease Laboratory), University of Minnesota, St Paul, MN 55108, USA

³ CIMMYT, P.O. Box 5186, Kathmandu, Nepal (Present address: CIMMYT, Lisboa 27, Apdo. Postal, 6-641, 06600 Mexico, D.F., Mexico)

Email: iariindore@sancharnet.in

Accepted for publication: 20 September 2001

Citation: Cereal Rusts and Powdery Mildews Bulletin [www.crpmb.org/] 2001/0920mishra

Four single-spore isolates derived from a leaf rust (Puccinia recondita) sample collected from wheat cultivar Sonalika in Nepal during 1994 (Collection No. 94NPL4008) were analysed for virulence at the Cereal Rust Laboratory (now Cereal Disease Laboratory), St. Paul, USA, using the current North American leaf rust differentials (Long and Kolmer, 1989) and an additional set of four Thatcher backcross lines carrying singly the leaf rust resistance genes Lr10, 18, 21 and 23. One of the above mentioned isolates (94NPL4008-1) showed virulence to the Thatcher backcross line carrying Lr24, the leaf rust resistance gene derived from Agropyron elongatum (now Lophopyrum elongatum). The race designation determined for this isolate was 'TFHR' with the following avirulence / virulence pattern in regard of the Thatcher backcross lines (Tc+) carrying singly 16 different leaf rust resistance (Lr) genes: Tc+Lr3ka, 9, 16, 17, 21 / Tc+Lr1, 2a, 2c, 3a, 10, 11, 18, 23, 24, 26, 30.

There is no other report of virulence to Lr24 from Nepal or India. Since central Nepal serves as one of the primary foci of leaf rust infection for the wheat crop in the Himalayan foot hills, and the eastern and north western plains of India (Joshi et al., 1985), occurrence of virulence for Lr24 in Nepal is a cause of concern for wheat production in India. The gene Lr24 is being used in the Indian wheat improvement programme, and three wheat cultivars, Amar (HW 2004), Vaishali (DL 784-3) and Vidisha (DL 788-2) carrying this gene have recently been released for commercial cultivation. Hence, wheat disease survey and surveillance in India needs to be strengthened to enable early detection of any Lr24-virulence. Furthermore, the Lr24 resistance in the current and future wheat cultivars in India needs to be complemented by other leaf rust resistance genes like Lr9, Lr19, Lr25, Lr28, Lr32, Lr37 and Lr45 which are highly effective against Indian leaf rust populations (Tomar and Menon, 2001).

The senior author is grateful CIMMYT-Mexico for financial support of his studies at the University of Minnesota. Thanks are due to Dr K.J. Leonard, Director, Cereal Rust Laboratory (now Cereal Disease Laboratory), St. Paul, USA, for providing guidance and facilities.

Joshi LM, Srivastava KD, Singh DV, 1985. Monitoring of wheat rusts in the Indian sub-continent. Proceedings of the Indian Academy of Science (Plant Science) 94, 387-406.

Long DL, Kolmer JA, 1989. A North American system of nomenclature for Puccinia recondita f.sp. tritici. Phytopathology 79, 525-29.

Tomar SMS, Menon MK, 2001. Genes for resistance to rusts and powdery mildews in wheat. 152 pp. Indian Agricultural Research Institute, New Delhi 110 012, India.