Recently, we identified two monosomics among progenies of soybean primary trisomics
(2n = 41).
All 146 [F.sub.1] plants involving T31 crosses with 14 other primary trisomics
had either 2n = 40 or 2n = 41 chromosomes, as expected.
Furthermore, progenies of MAALs with small seed consisted of mostly plants with 2n = 41 chromosomes (Singh, unpublished data), which is similar to that recorded in the primary trisomics
of many crop species (Singh, 1993).
Of the 220 [F.sub.1] progeny analyzed, five were trisomic
, 148 disomic, 60 monosomic and seven had 40 chromosomes.
First, there is a prevalence of trisomics
(hyperploidy) over monosomics (hypoploidy) among spontaneous abortions and liveborns (Hecht and Hecht, 1987).
speltiodes, transfer of leaf rust resistance from Aegilops umbellulata to wheat, and use of balanced tertiary trisomics
for breeding barley hybrids are some of the elegant examples of the use of cytogenetics in plant breeding.
Studies on the trisomics
in rice plants (Oryza sativa L.) I.
Cromosomal assignment of the nine linkage groups of sugar beet (Beta vulgaris L.) using primary trisomics
The complete set of twenty primary trisomics
for soybean (2n = 40 + 1) were provided by T.
In soybean [Glycine max (L.) Merr.], the complete set of primary trisomics
(2x + 1 = 41) has been difficult to establish because mitotic metaphase chromosomes are morphologically indistinguishable.
Palmer (1976) made an early attempt to develop primary trisomics
The two monosomic plants were identified among progenies of triplo 3 (B[C.sub.3]) and triplo 6 (B[C.sub.4]) trisomic
plants, backcrossed to 'Clark 63' as the recurrent parent.