Section 12 — Plasmatic Inheritance 



TV. tabacum in sylvestris cytoplasm and syivestris 

 in tabacum gave typical tabacum or sylvestris 

 plants, indicating that the sylvestris parent had 

 provided the cytoplasm in the original hybrid 

 from which N. tabacum was derived by am- 

 phiploidy. Association of tabacum with cyto- 

 plasm of certain Australian species and bigelovii 

 resulted in the development of split corollas and 

 complete pollen sterility. When plumbagimfolia 

 cytoplasm was involved, corollas were reduced 

 in size and there were only scanty amounts of 

 pollen formed. In the combination, tabacum 

 chromosomes with rustica cytoplasm, plants were 

 normal tabacum in appearance and had abun- 

 dant germinable pollen. They were fully female 

 fertile but, when selfed, set only an occasional 

 small capsule with a greatly reduced number of 

 seeds in each. When pollen of this type was 

 applied to stigmas of tabacum, virtually all 

 pollinated flowers abscissed. 



12.11. Nucleo-cytoplasmic Interactions. Luis B. 

 Mazoti and Ruderico S. Velasquez (Llaval- 

 lol, Argentina). 



A pure line of Zea mays (Selfing 20 ) was used 

 as male recurrent parent during 14 back-crosses 

 X Euchlaena mexicana. Among both lines of the 

 same homozygous genotype, which were differ- 

 ent only in their cytoplasm, were found the 

 following differential characters: 



(a) Significative of mean differences in per cent 

 of pollen sterility. In cytoplasm of Euchlaena, 

 x = 52.1 per cent, in cytoplasm of Zea, x = 8.8 

 per cent; «i + m = 480 anthers, P<i\ percent. 

 The environment affects the percentages, but the 

 signification is permanent. 



(b) Correlation in the percentages of pollen 

 sterility between neighbor anthers. In cytoplasm 

 of Zea, r — 0.575; in cytoplasm of Euchlaena, 

 r = 0.948; m + n% =-- 480 anthers. This results 

 are indicating that the initial factor responsible 

 of pollen sterility is independent from meiosis. 



(c) Significative of variance differences in the 

 nucleolus diameter. In cytoplasm of Euchlaena 

 V -■ 2.653 n, in cytoplasm of Zea V == 0.751 u, 

 ni + n2 = 86 and P<T per cent. This results 

 would indicate that the variance in nucleolus 

 diameter could be an index of the nucleo-cyto- 

 plasmatic harmony. 



(d) Significative of mean differences of the 

 Knobs volume. The Knobs volume in Zea cyto- 

 plasm is x = 17.41 |i 3 , in cytoplasm of Euch- 

 laena x = 26.62 m 3 , ni + « 2 = 960, P<1 

 per cent. This results could indicate that the 

 cytoplasm had modificated the chromosomic 

 structure. 



When, after 14 back-crosses of (Euchlaena x 

 Zea) ', Zea 14 , we obtain autofecundations, the 

 pollen sterility decreased in a significant measure: 

 x == 20.8 per cent in the back-cross to x = 16 

 per cent in selfing, m -f «a = 960 (anthers), 

 jP<T per cent. When this genome of Zea, which 

 was modified by the cytoplasm of Euchlaena, 

 was transported again to Zea's cytoplasm, an 

 increase of the per cent of pollen sterility is 

 produced from x = 8.92 per cent with the ori- 

 ginal genome) to x = 13.75 per cent (with the 

 recuperated genome), n\ + W2 — 1161, P<C\ 

 per cent. It wasn't changed in one year selfing. 

 This results would indicate that the variation 

 produced by Euchlaena' s cytoplasm on Zea's 

 genotype, are inheritable and favorable to 

 Euchlaena's cytoplasm and unfavorable (and 

 irreversible in S 1 ) to Zea's cytoplasm. 



The percentage of pollen sterility was esti- 

 mated in every "item" in base of 100 counted 

 pollen grains of one anther. 



12.12. Morphology, Cytology, and Biochemistry of 

 Male-sterile Lines of Maize. Patricia Sar- 

 vella and C. O. Grogan (Mississippi, 

 U.S.A.). 



Normal, cytoplasmic male-sterile, and restored 

 versions of five lines of maize were studied mor- 

 phologically, cytologically, and biochemically. 

 Measurements were taken from meiosis to 

 anthesis (about 15 days after meiosis). At an- 

 thesis only slight variations occurred in ear loca- 

 tion, ear height, tassel length , and number of 

 internodes to the ear. Some internodes and 

 sheaths above the ear, and tassel culms 

 and sheaths were shortened in the male- 

 sterile plants. Internode-sheath ratios show- 

 ed large differences between the versions. Stalk 

 lengths above the ear were correspondingly af- 

 fected which sometimes was reflected in the total 

 stalk length. Restored plants usually were shor- 

 ter than normal which could be attributed in 

 some cases to fewer internodes above the ear 

 rather than shorter internodes. Variations of the 

 different versions in different environments 

 showed a cytoplasmic-environmental interaction. 

 Pre-anthesis plants showed that shortening start- 

 ed in the male-sterile versions between 10 and 14 

 days after meiosis. At ten days after meiosis it 

 could even be the longest of the three versions. 

 The exact time of the shortening depended on 

 the line, on the internode location in relation to 

 the ear, and when elongation started. Pollen 

 degeneration in all lines occurred about 5 days 



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