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Wheat Information Service
Number 72: 3-8 (1991)


Production of D addition lines in tetraploid wheat: I. Cytology of F1 and F2 hybrids involving tetraploid and hexaploid wheats

A. K. Misra* and P. K. Gupta

Cytogenetics Laboratory, Department of Agricultural Botany, Meerut University, Meerut -250 005, India


Introduction

Spontaneous transfer of traits from some alien species to wheat under natural conditions has been established and some cultivated varieties of wheat, particularly those grown in Europe and USSR, are known to have whole chromosomes or segments of chromosomes from one or the other alien source (Gupta 1979). While on one hand the attempts to artificially incorporate such transfers have met with success in many cases, on the other they have generated valuable information regarding homoeologous relationships between wheat chromosomes and chromosomes from several alien species.

In hexaploid bread wheat, addition lines that carry a pair of alien chromosomes have been obtained using several related genera like Aegilops, Haynaldia, Secale and Hordeum. However, despite continued cultivation and utility, tetraploid wheats have received little attention for such chromosome manipulations. Joppa (1973) reported production of D genome substitution lines in durum wheats by crossing nullisomic-tetrasomic plants of hexaploid wheat with durum wheat. Yashvir and Kesavan (1979) obtained three monosomic addition and one double monosomic addition plants by selfing pentaploid hybrids produced by crossing hexaploid and tetraploid wheats. Joppa and McNeal (1972) and Joppa et al (1979) developed disomic addition lines for chromosomes 1D, 3D, 4D, 5D and 6D in durum wheat.

Since only limited work has been done towards production of addition or substitution lines in durums, there is a need to attempt addition or substitution of many more alien chromosomes to this crop. Such work may also generate valuable basic material for exploitation in wheat breeding programmes.


Materials and Methods

Reciprocal crosses were made between tetraploid wheat strains DD-21, Jairaj and ED-1570 and hexaploid wheat strains Sonora-64 and C-306. Nine F1 plants reached maturity. They were selfed to obtain F2 progeny. Emerging ears were bagged to avoid pollen contamination. Standard aceto-carmine squash technique was used for cytological studies.


Results and Discussion

The data on chromosome associations at metaphase I of meiosis of nine F1 plants are presented in
Table1. All the plants had expected number of chromosomes (2n = 35). Mean number of bivalents ranged between 13.88 to 14.00. As expected, the mode of the number of bivalents was 14. Mean number of ring bivalents per cell ranged between 10.44 to 12.20, with 11 being the most common number. For rod bivalents, mean/cell ranged from 1.80 to 3.52, with two modes (2 and 3). As expected, number of univalents in all the cases was 7 (Fig.1A), with the mean ranging between 7.00 and 7.24. The presence of a quadrivalent in AD2 (5) in a very low frequency could be due to homoeologous pairing or interchange heterozygosity.

In pentaploid F1 hybrids (2n = 35, 14" + 7'), the gametic chromosome number is expected to range between 14 and 21. Accordingly, the somatic chromosome number in F2 plants was found to range between 28 and 42. However, since the aim of the present experiment was to obtain disomic additions of D genome chromosomes to tetraploid wheat, the plants with more than fifteen bivalents were of no consequence.

* Present address: Department of Botany, North-Eastern Hill University, Mayurbhanj Complex, Nongthymmai, Shillong-793014, Meghalaya, India

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