The experiment was conducted using 2 popular varieties Suvarna belonging to A. cruentus and GA2 belonging to A. hypochondriacus having 7 contrasting characters, having gametic chromosome numbers, n = 17 and 16 respectively. The details of parents involved in the experiment are given in Table1. The parents, F1 and F2 population images can be seen in Fig. 1.
Table 1
Parents involved in the study for analysis of segregation ratio.
variety
|
species
|
Chromosome no.
|
Released from
|
remarks
|
Suvarna
|
A. cruentus
|
2n = 34
|
Banglore,1992
|
Green, Plum, drooping and semi spreading panicle having green leaves and stem.
|
GA2
|
A. hypocondriacus
|
2n = 32
|
S.K. Nagar, Gujrat, 2002
|
Red, erect, compact panicle having redish leaves and stem.
|
Intraspecific crosses were performed between the varieties with contrasting traits. Emasculation in females were done during evening hours and the emasculated flowers were pollinated the next morning and bagged with butter paper bag in order to prevent fertilization by undesirable pollens. Then hybridity test was done for the F1 generation using SSR marker. The plants obtained in F1 generation were Heterozygous and Homogenous in nature. The characters obtained in the F1 generation were identified as dominant characters. F1 hybrids were then proceeded to F2 generation.
Under field circumstances, several segregating F2 populations were scored for various attributes. The leaf marks were scored 4 to 8 weeks after emergence since this is when they are most expressed, and beyond this time the colour start to fade. The seedling coloration was evaluated immediately after germination. The flowering time was scored at panicle initiation stage. At maturity, the colour of panicle, plant growth habit, inflorescence shape and inflorescence spinney were scored.
The F1 and F2 populations were counted and analysed independently for each trait to determine the mode of inheritance. The χ2 (Chi-square) test as suggested by Fisher (1936) was used to confirm the obtained ratio with the expected ratios. χ2 analysis was done using the free online software, “Graphpad” by Dotmatics in which all we have to do is write down the characters, observed and expected data of the characters and it will give the detailed χ2 analysis report.
The mathematical formula of χ2 analysis is given as follows:
The calculated value of χ2 (Chi-square) was compared with tabulated values for (n-1) degrees of freedom. If the calculated value of χ2 was less than the table value of χ2 for (n-1) df at 5% level of significance, then the difference between observed and expected values were treated to be non-significant. The non-significant χ2 value indicated agreement between proportion of plants with parental traits and assumed ratio in F2 population, thereby leading to acceptance of hypothesis. In the present study the χ2 calculated values were compared with χ2 table values on various degrees of freedom for F2s as mentioned in Table 2
Table 2
The χ2 analysis result of different characters
Character
|
F1 reaction
|
F2 reaction
|
|
No. of plants
|
Ratio
|
χ2 value
|
P value
|
df.
|
|
|
|
Total
|
|
|
Leaf Colour
|
Green Leaf
|
55(Red leaf)
|
84(Dark leaf)
|
142
(Green Leaf)
|
281
|
3: 4: 9
|
4.421
|
0.1096
|
2
|
Panicle Colour
|
Red panicle
|
169 (Red panicle)
|
97 (Green panicle)
|
15 (Intermediate panicle)
|
281
|
9: 6: 1
|
1.797
|
0.4072
|
2
|
Flowering
|
Late
|
147 (Late)
|
85
(Intermediate)
|
39
(Early)
|
281
|
9: 3: 4
|
0.596
|
0.7424
|
2
|
Plant Growth Habit
|
Spreading
|
234 (Spreading)
|
47 (Erect)
|
|
281
|
13: 3
|
0.759
|
0.3837
|
1
|
Red Leaf Margin
|
Having Red Leaf Margin
|
201 (with Red Leaf Margin)
|
80 (Without Red Leaf margin)
|
|
281
|
3: 1
|
1.903
|
0.1678
|
1
|
Inflorescence Shape
|
Erect
|
184 (Erect)
|
81 (Curved)
|
13 (Bushy)
|
281
|
9:6:1
|
5.187
|
0.0747
|
2
|
Inflorescence Spiney
|
Flat
|
227 (Flat)
|
54 (Spiney)
|
|
281
|
13: 3
|
0.023
|
0.8788
|
1
|
Stem Colour
|
Green
|
221(Green)
|
60 (Green)
|
|
281
|
3: 1
|
1.994
|
0.1579
|
1
|
Inflorescence Compactness
|
Compact
|
202(Compact)
|
79(Spreading)
|
|
281
|
3: 1
|
1.453
|
0.2280
|
1
|