Variation in genotypic responses of Indian hexaploid wheats for haploid production in crosses with maize
G. Najafian* and T.B. Singh
Department of Genetics and Plant Breeding, College of Agriculture, G.B. Pant University of Agriculture & Technology, Pantnagar 263 145, Uttaranchal, India
Summary
To study genotypic effects of wheat plant on haploid production through wheat x maize crossing, five F1 hybrids of wheat (W1-W5) obtained from crossing of different hexaploid wheat varieties were pollinated with pollen from a composite variety of maize Kanchan in outdoor conditions. Cut glume method was used for emasculation. Hormonal treatment was 75 ppm solution of 2,4-D for two days after pollination and 300 ppm solution of gibberellic acid on the 3rd day. Seed set, rates of embryo formation, embryo germination and plantlet recovery were studied. Seed set was not directly affected by wheat genotypes. Response of wheat genotypes was different for embryo formation rate. The best genotype was W1 with 12.8% embryo formation, while the poorest genotype W2 showed 2.5% embryo formation. The pollen tube growth measurements inside the stigma conducted on W1 and W5 crosses showed a significant difference; W1 had a higher mean of pollen tube length than W5, which was in agreement with their embryo production percentage. It was suggested that growth of maize pollen tube inside the stigma of wheat genotypes followed by embryo production might be under control by some unknown crossability systems different from that by Kr genes. No genotypic effect was observed for embryo germination and plantlet recovery.
Key words: genotypic effects, haploid production, Triticum
aestivum, wheat x maize crosses.
Introduction
Haploid breeding has potential of integration in wheat breeding programs, because of the production of homozygous lines from F1 generation of a particular cross within a short period of time compared with other traditional methods. To be used successfully and cost-effectively in a breeding program any particular doubled haploid (DH) system should fulfil the following three criteria. (Snape et al. 1986). These are 1) easy and consistent production of large number of DHs of all genotypes. 2) DHs should he genetically normal and stable and 3) DHs should contain a random sample of the parental gametes.
Production of wheat haploid plants through wheat x maize crossing, which at first was performed by Laurie and Bennett (1988), appears to fulfil above three criteria. This method has been suggested as a more perfect procedure of haploid induction in hexaploid wheats compared to the earlier procedures including anther/microspore culture and bulbosum system. So far several studies have reported the genotypic effect of wheat parent for percentage of embryo formation (eg Suenaga et al. 1991; Riera and Mujeeb-Kazi 1993; Giura 1994; Sadasivaiah et al. 1999). Some of these studies have shown the ineffectiveness or less effect of Kr crossability genes in wheat x maize crosses but still it is not fairly clear whether these genotypic effects are output of a crossability system (Laurie and Bennett 1987). The Kr crossability genes are effective through preventing or reducing the growth rate of male parent pollen tube inside the style or ovary of wheat flowers in case of wheat x Secale cereale and wheat x Hordeum bulbosum crosses. In consequence, there would be no or less number of embryos in such crosses( Falk and Kasha 1981, 1983; Sitch and Snape 1987).
In this study, through crossing of Indian hexaploid wheat genotypes with maize, the genotypic effect of wheat parent was studied on some characteristics of wheat x maize crosses including pollen tube growth.