4. Trisomics - Seed weight. In order to get a relatively high frequency of trisomic plants the smaller seeds are often selected from a trisomic ear. A study was made to find how close a correlation exists between weight of seed and chromosome number and whether this correlation varies in different trisomic stocks.

Random samples of from 50 to 150 seeds were taken from trisomic ears. In some cases, however, only relatively small numbers of seeds were available. Each seed was weighed to the nearest .01 gram and placed in its weight class. In most cases the weights when plotted against number formed a unimodal curve In some, however, bimodal curves resulted (see III × lg2). The seeds were germinated in trays and roots taken before transplanting to the field. The results are expressed in table 1.

 

Table 1

Relative
length of
extra
chromosome		 Trisomic Stock Weight
of seed
in mg.		 % trisomics No. of
individuals		 %
trisomics in
random sample		 No. of
individuals
 
85 II × L.F. Inbred 140-210 82 38  
  220-230 53 59 50 139
  240-260 19 42  
 
  II × Inbred II 160-220 14 7  
  230-240 56 16 37 43
  250-280 30 20  
 
  II × C. II Inbred 130-200 87 30  
  210-230 49 35 52 93
  230-260 18 28  
 
  II × lg 130-180 80 5  
  190-200 61 18 39 52
  210-240 17 29  
 
79 III × L.F. Inbred 150-240 69 16 35 34
  250-300 6 18  
 
  III × Inbred II 100-150 50 12  
  160-180 40 20 33 52
  190-230 15 20  
 
  III × lg 2 140-160 100 31  
  170-180 50 16 45 91
  190-240 5 44  
 
78 V × Inbred II 120-160 65 52 52 89
  32 37  
 
60 VI × su2 140-200 77 30  
  210-220 12 42 30 103
  230-260 10 31  
 
60 VII × L.F. Inbred 70-110 73 11 45 22
  120-150 18 11  
 
  VII × Inbred II 70-120 63 16  
  130-140 39 23 40 58
  150-200 21 19  
 
60 VIII × L.F. Inbred 110-170 63 38  
  170-180 44 43 32 146
  190-220 6 65  
 
  VIII × j 200-230 33 18  
  240-260 33 18 .27 45
  270-320 0 9  
 
52 IX × v wx 120-160 46 13  
  170-180 71 24 22 113
  190-220 3 76  
 
45 X × L.F. Inbred 220-250 48 54  
  260-270 12 52 26 149
  280-310 12 43  
 
  X × v18 200-230 58 12  
  240-250 35 20 37 49
  260-270 24 17  

 

Table 2

Relative
length of
extra chromosome		 Trisomic
stock		 Percent
2n + 1
plants
in progeny		 No. of
individuals		 Percent
microspores
with n + 1
chromosomes		 No. of
individuals
     
85 II. x L.F. 50 139 50 212
79 III. x lg2 45 91 41 167
45 X x L.F. 26 149 34 190
  X x v18 37 49 33 109

 

Relative
length of
extra chromosome		 Trisomic
stock		 Percent microsporocytes
with univalents in Met. I		 No. of individuals
   
85 II. x L.F. 30 247
79 III. x lg2 - -
45 X x L.F. 49 372
  X x v18 37 300