1. Blotched leaf.

 

In June, 1944., a supply of seed of Hawaiian Yellow Field Corn was received from A. J. Mangelsdorf, Hawaii Sugar Planters Association. It was derived from crosses between many tropical and subtropical corns and was extremely variable. Several inbred lines were isolated from it and in these appeared plants showing protogyny, adherence and blotched leaves; the last‑named is discussed here.

 

Blotching appeared just before tasseling, at about 60 days; the spots were yellow, numerous, evenly scattered over the leaf and later became coalescent. They were not notably elongate; nor were they ever few in number and large in size with a necrotic centre as described by Emerson (Cornell Univ. Agr. Exp. Sta. Mem. 70, 1923). The present gene will be referred to as Bl3-bl3.

 

There was some variation of expression in different cultures but recessivity was complete and classification easy.

 

Some families segregated also for light red vs. green plant colour (table 1).

 

Table 1. Segregations

 

 

Red

Green

Parentage

Normal

Blotched

Normal

Blotched

 

 

 

 

 

Red‑normals selfed

62

15

18

18

Red‑normal selfed

39

9

Red‑blotched selfed

37

-

10

Green‑blotched selfed

-

-

-

43

Red‑normal x Green‑blotched

16

6

2*

1*

Green‑normal x Green‑blotched

-

-

11

10

 

* Presumably plants with 'red' genotypes mis‑scored.

 

Single‑factor segregations are in agreement with expectation; but there is good evidence of coupling linkage (X2 = 15.03; crossing over 31.2 5.4% by the method of maximum likelihood). Which anthocyanin locus was concerned is not known, but it seems likely that it was R, which would place Bl3 in the tenth chromosome (Rhoades and Rhoades, Genetics 24: 302, 1939).

 

Blotched plants seemed to be slightly less vigorous than normals. This impression was supported by measurements of weights of fresh cobs in several families (table 2).

 

Table 2. Mean weight (gm.) of fresh cobs in segregating families.

 

Family

Normal

Blotched

Blotched as % of normal

28

113

51

46

25

87

68

79

51

227

118

52

26

108

85

79

21

147

81

55

 

 

 

 

Means

125

82

66

 

Differences between families and between the genes were significant at the 1% level.

 

N. W. Simmonds