3.4.45
GENERATION OF BLAST RESISTANT DOUBLED HAPLOIDS OF INDICA RICE

TR SHARMA, RS CHAUHAN, BM SINGH, MK RANA, V SAGAR and R PAUL

Biotechnology Centre, HP Krishi Vishvavidyalaya, Palampur, 176 062, India

Background and objectives
Blast caused by Pyricularia grisea is an important disease of rice in the north-western Himalayan region of India. Development of rice germplasm with durable blast resistance is a high priority area of research in this region. Resistant rice cultivars succumb to the pathogen within 2 to 3 years of introduction in these areas [1]. High levels of pathogenic variation, inadequate resistance screening and evaluation methods, and improper deployment of resistance genes alone or in combination have been suggested to cause breakdown of blast resistance under field conditions [2]. Therefore, identification of diverse sources of resistance against the pathogen population present in a particular epidemiological region has great significance in devising suitable blast management strategies and for the production of germplasm with durable blast resistance. The objectives of this study were to identify genes effective against P. grisea populations of the north-western Himalayan region and to transfer resistance gene(s) to the locally adapted cultivars using anther culture technique.

Results and conclusions
Fourteen international differential hosts possessing known gene(s) for resistance were tested against 55 isolates of P. grisea collected from different epidemiological regions of Himachal Pradesh, Jammu and Kashmir and Uttar Pradesh. All the P. grisea isolates were found avirulent on Tetep, whereas virulence frequency on Fukunishiwi and Tadukan was 1.82 and 3.64 %, respectively.

Fukunishiki and Tetep were crossed with three elite indica rice genotypes, HPU 741, HPR 842 and Ram Jawain, and two local cultivars, LCH 7 and LCH 9. Immature/mature embryos of different cross combinations were cultured on MS medium supplemented with kinetin (8-10 mg) + sucrose (30 g) + agar (8 g) per litre of the medium in order to obtain sufficient number of F1 seedlings. Anthers (3179) of F1 plants of the cross Fukunishiki x LCH 7 were inoculated on different callus induction media. Maximum callusing (9.09%) was observed on N6 + 2,4-D (2.0 mg/l )+ kinetin (0.5 mg/l) + sucrose (50 g/l) + agar (8 g/l). Calli (147) derived from anthers of F1s of Fukunishiki x LCH 7 were cultured on different regeneration media for developing doubled haploid (DH) lines. Of these, 17% calli differentiated into plantlets on MS medium containing BAP (1.0 mg/l), kinetin (1.0 mg/l) and NAA (0.5 mg/l) and 27% calli produced albino plants. Similarly, results on plant regeneration were obtained with other cross combinations. More than 67% DH lines of Fukunishiki x LCH7 were found resistant to P. grisea under artificial inoculation conditions. Use of these DH lines in developing durable indica germplasm with durable blast resistance and tagging of Pi-z blast resistance gene in Fukunishiki with molecular markers will be discussed.

References
1. Kumar J, Nelson RJ, Zeigier RS, 1996. Second lnt. Crop Science Cong., New Delhi.
2. Ou SH, 1979. In Proc. Rice Blast Workshop. International Rice Research Institute,Manila, Philippines, pp. 81-137.