20 



THE AGRICULTURAL NEWS. 



January 25, 1919. 



NOTES ON INHERITANCE IN THE 

 COWPEA. 



THK COLOUR OK THE SKED COAT PATTERN. 



Mr. .S. C Harland. B.Sc, has furnished us with the 

 following note in c ntinuation of his investigations on inheri- 

 tance of characters in the cowpea. 



A paper by the writer, shortly to be published in the 

 Joiirihi! (if Gi'iietics, contains data on the inheritance of three 

 factors which affect the colour of the seed coat pattern. 

 These are as follows: — 



B. The factor for Black. Dominant to Red, Brown, 



and Maroon; also causes colour to appear in the 

 calyx, peduncle, and tip of young pod. The New 

 Era factor (E) also produces colour in these regions 

 but of less intensity. 



N. The factor for Brown. Dominant over Maroon, and 

 over Red. 



M. The factor for Maroon. Incompletely dominant 

 over Red. 



In a cross between lilack and Brown the F., ratio was .3 

 Black to 1 Brown. The F.^ ratio of a cross between Brown 

 and Red was 12 Brown : 3 Maroon : 1 Red, i.e. the cross wa.s 

 N M (Brown) by n m (Red). The F., types were 9 N M 

 (Brown), -3 N m (Brown), 3 n M (Maroon), and 1 n m (Red). 



The object of the experiments to be described in the 

 present note was to learn more about the geneiic constitution 

 of the albino type Para, which has a white or cream-coloured 

 seed. 



Para by Red. 



Red is recessive to all colours so far worked with, and it 

 was thought that a cross with I'ara would show whether the 

 latter contains any hidden colour factor. 



The F, was Brown, of the same shade as the Brown 

 type N rii alluded to above. In the F.^ segregation occurred 

 into Brown, Red, and White, thus: — 



The numbers obtained are olose to expectation, and it 

 is probable that the cros.s involves two independently inher- 

 ited factors: — 



R, the factor for Red. 



\, the factor for Brown. X has no visible effect in 



ab.sence of 11. 



Red is a solid type, and it also possesses anlhocyanin in 

 stem and leaf axil. Thus its constitution is probably 

 X W H n R, while that of I'ara is X W H N r. It will 

 be noted that Para is asauined to contain the antho- 

 cyanin factor X. If Para did not contain this factor. 

 we .should expect to obtain in F.^ plants with Red 

 seeds but with no anth' cyanin in the vegetative part.s. 

 Such types are known to exist, but they do not appear in 

 Ihis cross. If Para does contain X, the latter is another 

 factor which cannot appear except in presence of the basal 

 factor for pigment in the sc'l coat, which may now bo 

 called 1! 



Piira hv Maroon ll'afson. 



Para does not contain the Maroon factor M, for no 

 Maroon types appear in the cross Para by Red. Thus its 

 constitution may be rewritten X W H N m r. Para w;is 

 crossed with a Maroon with Watson eye, the constitution of 

 which was X W h n M R. The F, should be Brown Solid. 

 An F,, family of twelve plants gave the expected result, but 

 the F.J was not grown. 



Para ly Black. 



Two crosses were made. The F,' was Black, and in the 

 F.J, segregation occurred into Black, Brown, and White in 

 the 9: 3: 4 ratio. 



Black. 

 Family 1 16 

 i 26 

 Total 42 



Expectation 42 75 



The first cross was with a Black Solid, and from what is 

 known of the genetic constitution of Para, it is probable that 

 a correct representation of the factors involved is as follows: — 



Black (B W H N R X) by Para (b W H N r X) 



The cross being a bifactorial one, the F.j 

 9 B R : 3 R r : 3 b R 



tyyes will be: — 

 : 1 br 

 Black While Brown White 



Thus the factor B has no effect except in presence of R. 

 The similarity between the results of this cross and that of 

 the Para by New Era cross is obvious. 



In the second cross, the Black parent was the variety of 

 Black eye which lacks the Watson and Holstein factors 

 (W and H). and is therefoic presumably of constitution 

 B w h N R X. It has preriously been argued that Para 

 i.s really a Solid type, but no pattern is vi.sible on the seed 

 coat owing to the absence of the factor R. Para has a white 

 flower. Black eye not having the Watson factor, has a pale 

 flower. If Para contains the factors for Solid colour, W and 

 H, the F, of a crnjs with Black eye will be Dark flowered, 

 with the pattern Solid colour, and in the ¥ .. , the following 

 types should appear: — 



Black Solid, I'.lack Watson, Black Holstein, Black eye. 

 Brown Solid, Brown Watson, Brown Holstein, Brown eye, 

 and Albino. All these were recorded except Brown eye, but 

 as this type is only expected to occur in three plants out of 

 2.56, its absence in a family of fifty plants need not occasion 

 surprises. The results of this cross in regard to the inheri- 

 tance of pattern, are as follows: — 



.Siilid AVatson Holstein Stnall eye 

 (WH) (Wh) (wH) (w h) 



« 3 1 



Expectation on 

 9;;5:3:1 basis 



24 



21-6 



•2 



2-4 



These results arc fairly close to expectation, and confirm 

 the suggestion that the albino type Para contains W and H, 

 the' factors for Solid colour. 



.SUMMARY. 



In cowpeas there is a factor R which produces a Red 

 colouration of the seed coat pattern. In the absence of this 

 factor no pattern c;ui appear on the seed coat, and thus the 

 factors which liavr been mentioned as responsible cither for 

 the production of pittern or foi variations in the colour of 

 the seed coat piiLiirn are without effect in absence of R. 

 These factors are: — 



I! (Black), X (I'.rown), M (.Mamon), X (factor for antho- 

 cyanin in stem and leaf stalk), W (Watson eye), and H 

 fllnl^tcin pafLcrn). 



