| Genetic pistillody in New Zealand wheat
H. E. CONNOR and A. W. PURDIE Botany Division, Department of Scientific and Industrial Research, Christchurch, New Zealand When anthers of the wheat flower show various degrees of transformation towards the form of the gynoecium the phenomenon has been called pistillody (LEIGHTY and SANDO 1924) carpellody (CALDER 1930) and multiple-carpel (BHATIA and SWAMINATHAN 1963). It has been reported, and abundantly illustrated, from apparently normal wheat (LEIGHTY and SANDO 1924), in nuclear substitution lines incorporating cytoplasmic male sterility (KIHARA 1951, 1966, 1967, KIHARA and TSUNEWAKI 1961, 1967), in progenies from irradiated seed (BHATIA and SWAMINATHAN 1963), in two hybrid generations of New Zealand wheat (CALDER 1930), and in Triticum-Agropyron hybrids (TSITIN and LUBIMOVA 1959). In nulli-6B and nulli-7A lines of cv. Chinese Spring, SEARS (1954) found pistillody fairly common but this character was suppressed in the monotelo- and mono-isosomics. No simple genetic ratios were obtained in any experiments, but CALDER, and BHATIA et al. concluded that pistillody was a heritable recessive character. Pistillody was recently seen in one of 10 families involving repeated backcrossing of a standard New Zealand wheat cultivar-Aotea1). Nine plants in this family of 31 displayed pistilloid anthers varying from a few stigmatic hairs on an anterior anther to the complete transformation of all stamens into gynoecia. Not all florets in a spike bore pistilloid anthers. Such variability in expression within florets, spikelets, and spikes of the same plant has been detailed by most of the authors cited above. In the records presented here plants were classified as pistilloid if any anther displayed pistilloid characteristics. Small F3 families were raised from 19 of the 22 normal F2 plants. Fourteen of these families contained plants classified as pistilloid while 5 families contained no abnormal plants (Table 1). These results would fit the action of an autosomic pair of alleles with the homozygous recessive permitting the development of pistilloid anthers. The F2 would fit a 3: 1 segregation (x12=0.24); two thirds of the normal F2 plants segregated both normal and pistilloid types in F3 (x12=0.4) indicating heterozygous F2 genotypes. Among the 14 segregating F3 families there was non-significant heterogeneity (x132=8.38), and a good fit to a 3: 1 ratio (x12=1.04). This genetic solution may be an over simplification. The expression of pistillody was rarely complete-as few as 10% in some spikes-and would fit BHATIA and SWAMINATHAN'S suggestion that pistillody is a character of low expressivity and low penetrance. KIHARA (1951), and KIHARA and TSUNEWAKI (1961) are emphatic that environmental effects, especially day length, are important in the expression of the pistilloid potentiality. Here,all F2 and F3 families were raised in growth chambers with temperature and light control. |
| 1) Aotea7 x A Federation 2 x Aotea7 x 1066/1 3 x Aotea6 x Hilgendorf 61. |
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