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Wheat Information Service
Number 88: 21-26 (1999)
Research article

Transfer of alien genes Lr9, Lr24 and Lr28 to bread wheat cultivars susceptible to leaf rust

R. N. Brahma, M. Sivasamy and Aloka Saikia

Indian Agricultural Research Institute Regional Station, Wellington, The Nilgiris, Tamilnadu, India


Summary

Twelve wheat lines (VA92-10, CR7, CLRP-6, DW876, DW880, CPAN4166, CPAN4167, CPAN4168, Veery's', HW741, HD2329 and HD2285) possessing good agronomic traits but susceptible to leaf rusts under natural epiphytotic conditions at Wellington were chosen from different nurseries grown under All India Coordinated Wheat Improvement Program. They were crossed with HW 2005 (carrying Lr24+Sr24), PH 127 (carrying Lr9) and HW 2037 (carrying Lr28) which were conferring high degree of resistance at Wellington, to obtain specific crosses. The resistant progenies to stem, leaf and stripe rusts were constituted at BC3F5 stage. The constituted lines were evaluated for three seasons under natural epiphytotic conditions (The predominant races of leaf rust pathotypes include 11, 77A, 77-1, 77-2, 77-5, 104B and 16, stem rust pathotypes are 11, 40, 40A, 40-1, 117, 117A and 117-1 and stripe rust pathotype I). The seedling tests were also carried out under glasshouse conditions against the individual races of stem, leaf and stripe rusts, predominantly prevalent in the Nilgiris, South India. The resistant lines to all the three rusts will be useful in combating the rust at foci of rust.


Introduction

Leaf rust caused by Puccinia recondita f. sp. tritici is the most important and destructive disease on wheat in India (Joshi et al. 1986; Anand et al.1969; Evermeyer and Browder 1974; Sawhney et al. 1977). In the past several successful attempts were made to develope resistant wheat lines to leaf rust but time to time the varieties became susceptible due to occurrence of new virulence. Hence, the exploitation of specific rust resistance genes to combat the rust gains paramount importance.

Transferring these genes into different genetic background will offer a useful solution by way of durable resistance in the new lines. Though Van der Plank (1963) advocated development of rust resistant lines with horizontal resistance to have durable resistance, Johnson (1981) opined that the horizontal resistance which are apparently non specific to pathogenic races it may be difficult to identify, evaluate and recover in breeding programs and still there is no guarantee that the resistance so introduced would be permanent. Considering these factors the practical approach would be to deploy the known rust specific genes under different genetic background and it will act as a mosaic to combat the rust in an environment favoring the disease. Therefore, we have to depend mainly on the alien sources of resistance genes and exploiting its interculture nature under different genetic background.

Over 30 key rusts resistance genes (Lr genes) have been identified from different sources and designated as Lr1 through Lr35 (McIntosh 1988). Out of which none of the specific genes from Triticum aestivum was found to offer complete resistance and only alien source of rust resistance genes viz. Lr9, Lr19, Lr24, Lr28, Lr31 and Lr32 are found to offer excellent resistance (Gupta 1985). In the present study an attempt was made to transfer the alien genes Lr9, Lr24 and Lr28 to different genetic background to develope resistant lines.

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