In vitro screening and production of karnal bunt resistant doubled haploids in wheat
Naveen Singh, R. K. Behl, M. S. Punia and Vikram Singh
Dept. of Plant Breeding, CCS Haryana Agricultural University,
Hisar-125 004, India
Summary
Two Karnal bunt susceptible wheat varieties viz. UP2338 and WH533 were crossed with two Karnal bunt tolerant varieties viz. HD2285 and PBW343. Resultant F1's were crossed with different maize lines (pollinator) and embryos were rescued between 13 to 16 days post pollination. To enhance embryo survival, 2,4-D + GA3 solution was injected in the upper node and also applied in the florets. Rescued embryos were cultured on MS medium containing 5mg/l 2,4-D. The callus as well as the callus regenerated haploid plantlets were screened in vitro at threshold concentration of culture filtrate. The resistant haploid calli and plantlets were selected and plated on colchicine mediated MS medium for doubling their chromosomes and production of Karnal bunt resistant doubled haploids.
Key words: wheat, karnal bunt, wide hybridization, wheat x
maize cross, doubled haploid
Introduction
The Karnal bunt (KB) of wheat caused by Neovossia indica (Mitra) Mundkur has been of great concern worldwide. Beside India and Pakistan, KB is reported from Syria (Williams 1983), Afganistan, Mexico (Joshi et al. 1983), Nepal (Singh et al. 1989), USA (Yakema et al. 1996) and Iran (Torarbi et al. 1996) etc.
Karnal bunt causes heavy losses during epidemic years and adversely influence wheat grain end use quality and thus consumer acceptability besides quarantine related procedural wrangles create trade barriers. KB is difficult to control by seed treatment by fungicides. Moreover, genetic variability for KB resistance is limited, therefore, wheat improvement program for KB resistance must proceed with creation of novel genetic variability through in vitro methods as the conventional breeding has not paid much dividend. Studies have shown that genes for KB resistance are scattered over a number of wheat genotypes. Concentration of favorable alleles governing Karnal bunt resistance and high yield in few genetic backgrounds is one of the most important task, wheat breeders would like to accomplish. Any method, which offers infinite F2 population in homozygous state, would cut short breeding time and help increase selection efficiency for KB resistance. In this context, doubled haploid (DH) technique would facilitate creation of new genetic variability in the form of multitude of homozygous true breeding lines. Wheat x maize crosses, being free of crossability alleles, have proved efficient mean of haploids and hence doubled haploids production.