Section 13 — Plant Genetics and Breeding 



ditions are as follows: for the pupil plant: of a 

 less advanced age than the mentor-plant and 

 total removal of leaves all along evolution; for 

 the mentor plant: maintenance of leaves and 

 absence of flower-buds which are cut off as soon 

 as they appear. 



The influence of the black nightshade mentor 

 on the "white round" eggplant pupil became 

 apparent only in the offsprings of the third 

 generation of grafts. Out of 7 symbionts carrying 

 fruit at the third generation of grafts, 2 offer in 

 their descendency an alteration that so far 

 prevailed down to F3: the colour of the stem is 

 slightly purple. These anthocyanins are extreme- 

 ly thermolabile. Chromatographic analyses made 

 so far show the Rf of anthocyanins to be differ- 

 ent from those found in the black nightshade. 



In these interspecific grafts we did not observe 

 any mentoi -oriented alterations. However, the 

 new traits that have become apparent in the 

 descendency of both modified plants are of the 

 same type, therefore, the influence of the mentor 

 may be assumed to work in both pupils in the 

 same direction. 



Article to be published in: Comptes rendus des 

 seances de la Societe de Biologie de France, 1963 ; 

 Archives des Sciences de Geneve, 1963. 



13.30. Alteration of Traits obtained in Solanum 

 melongena as a Consequence of Inter-variety 

 Grafts. M. Stroun and J. Stroun (Poitiers, 

 France). 



The "Early Violet" variety was used as mentor- 

 plant and the "White Round" variety as pupil- 

 plant. The mentor-epibiont / pupil-hypobiont 

 grafting procedure is applied as follows: the 

 pupil-plant is totally rid of its leaves all along 

 its development, whereas the mentor-plant 

 retains its foliage but is rid of its flower buds 

 which are cut off. The graft is repeated on each 

 new generation until alterations appear. Sexual 

 crossbreeds were also made "White Round" § x 

 "Early Violet" $. 



The 19 homografted "White Round"/"White 

 Round" controls did not show any alterations. 



The influence of the mentor-plant "Early 

 Violet" on the pupil variety "White Round" 

 appeared only at the third generation of grafts. 

 Out of 24 fruit-bearing symbionts, 9 presented 

 various alterations in fruit and stem colour, 

 shape of fruit, or in a trait of the stamen. These 

 alterations resemble the traits of the mentor 

 variety. They are found again in the sexual 

 descendants of the modified symbionts, studied 



so far down to F2. They often differ from the 

 characteristics conveyed by sexual crossings 

 between the two varieties used. There is a dis- 

 junction in Fi, only part of the alterations being 

 transmitted. Futhermore, new traits appear on 

 certain plants. To all appearances therefore, 

 grafts, as practised by the authors, seem to 

 influence the hereditary traits of a given variety. 



C. R. Acad. Sci. 255, 561-563, 1962; Arch. Set. 

 Geneve, 1963, to be published. 



13.31. To a Correlation of the Objectives in 

 Tree Breeding. C. Lazarescu and E. San- 

 duleac (Bucharest, Rumania). 



Since trees constitute the most constant 

 vegetable covering of the earth, the approaching 

 of the problem of tree breeding from the point 

 of view of timber production — as that is 

 applied usually in forest genetics — is only a 

 single aspect of this question. 



The multilateral task of trees in nature requires 

 a simultaneous correlation of the objectives in 

 their breeding: (a) fast growth and higher 

 quality of the timber; (b) resistance to damages 

 by biotical and abiotical factors and the achieve- 

 ment of a stable biological balance within the 

 biocenoze; (c) increase of the task for protection 

 of nature (soil, sources, rivers, mineral water 

 sources, etc.); (d) increase of their healthy and 

 aesthetical task in the crowded centres. 



We refer here as an example to the breeding of 

 black locust in Rumania. In the best conditions 

 (light but rich sandy soils and more than 11 °C 

 annual mean temperature), the 25-30-year-old 

 stands of this species realize yearly mean growths 

 up to 18 m 3 per hectare. As a first objective in 

 the breeding of black locust cultivated in this 

 country, we have in view to propagate the de- 

 scendants of the plus trees, which give maximum 

 growth and better properties of the wood. 



Regarding the second objective, we have 

 identified a few hybridogenous populations ob- 

 tained in the cultivation (Robinia pseudacacia 

 R. viscosa and R. pseudacacia R. neomexi- 

 cana), which realize a more large biocenoze, 

 due to their more marked entomophyll character 

 and their increased resistance against frost and 

 disease. At the same time, these hybrids are 

 faster in growth and give a higher nectariferous 

 production (0.0700 g bloom instead of 0.0460 g, 

 at the 62-63 per cent concentration). 



On the other hand, the black locust is fre- 

 quently used in erosion control and sand 

 fixation. The selection of the forms with a 



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