Maize Genetics Cooperation Newsletter vol 84 2010

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of authors.

 

 DNIEPROPETROVSK, UKRAINE

               Institute of Grain Farming

 

Inheritance of matroclinal haploidy   in diallel crosses

    --Satarova, T N; Cherchel, V Yu

     Gynogenesis is   an apomictic pathway of reproduction when a new organism arises from an unpollinated egg cell and is called a matroclinal haploid.  First S.S.Chase  (Genetics 34: 328-332, 1949) has founded matroclinal haploidy in maize. E.H.Coe (Am Nat 93:381-382, 1959) and J.L.Kermicle (Sci 166:1422-1424, 1969) created   marker   lines   those permitted taking as pollinators to identify haploids in populations and to stimulate to some extent the ability to produce haploids. Now in maize breeding practice matroclinal haploids after diploidyzation are widely used for rapid production of homozygous lines.

     The investigation of genetic control of   matroclinal haploidy is actual both for the characterization of apomixis in flowering plants and for the forecast of the structures of synthetic populations which could become the initial material for    selection of new lines.  Inheritable peculiarities of this phenomenon should be taken into consideration also in   programs of breeding lines with high ability to haploid production to be used as testers in selection of marker genotypes.

     The aim of the given investigation was to analyse the inheritance of the ability to produce matroclinal haploids in maize. Genetic analysis was conducted in the system of full diallel crosses according to B.I.Hayman   (Biometrics 16: 369 - 381, 1960).  Five lines were included to diallel scheme, DК276-1, DК247, DК293, DК303/427, DК205/710, and their reciprocal hybrids.   25 genotypes in total were organized in 4 repetitions.   For production of matroclinal haploids   every genotype of diallel scheme was pollinated with pollen of marker genotype Zarodyshevij marker krasnodarskij 1 (ZMK-1). This marker    had been selected by E.R.Zabirova et al. (Kukuruza i sorgo 4: 17-19, 1996). It keeps dominant genes of   plumule   and endosperm coloration in purple. Seeds after pollination with ZMK-1 of all the genotypes of diallel scheme were harvested and haploids were   identified as caryopses with colourless embryos and coloured endosperm. Caryopses with haploid embryos were sown next year into the soil and grown to anthesis to verify their haploid status. ÒFrequency of matroclinal haploidyÓ was calculated as the percentage ratio of   the amount of caryopses with haploid embryos to the total    amount of caryopses with coloured endosperm.       According to our observations   after pollination of different maize populations with pollen of ZMK-1 grain amount per ear is greatly declined in comparison with free pollination (fig.1).   Such a character was   named   Òdegree of ear grainnessÓ, calculated as the   percentage ratio of average   grain amount   per ear after pollination with ZMK-1 to grain amount   per ear of the same genotype after free pollination, and also analysed in diallel crosses.

 

    Figure 1. Maize ears after pollination with marker genotype ZMK-1 show the declination of grain amount.

 

     The average values of two traits for genotypes of diallel set are shown in table 1.

Table 1. The frequency of matroclinal haploidy and the degree of ear grainness for inbred lines and hybrids of diallel set.

 Genotype

Frequency of matroclinal haploidy, %1

  Degree of ear grainness, %1

DК 276-1

6,45±0,73

27,46±2,73

DК 247

7,79±1,23

22,93±4,14

DК 293

8,07±0,77

38,18±3,47

DК 303/427

5,62±0,71

42,60±4,14

DК 205/710

0,59±0,22

50,12±4,39

DК 276-1хDК293

5,05±0,77

17,94±2,79

DК 293хDК276-1

7,00±1,08

28,77±3,07

DК 276-1хDК247

6,27±1,03

22,86±3,61

DК 247хDК276-1

5,67±0,97

33,02±3,53

DК 276-1хDК303/427

5,73±1,04

28,71±3,95

DК 303/427хDК276-1

6,58±1,07

34,79±4,37

DК 276-1хDК205/710

2,36±0,63

13,01±2,63

DК 205/710хDК276-1

3,30±0,95

12,22±2,14

DК 293хDК303/427

7,42±0,76

47,35±7,16

DК 303/427хDК293

7,71±0,77

48,11±5,48

DК 247хDК293

10,68±0,89

33,26±4,94

DК 293хDК247

11,12±3,15

25,17±3,59

DК 293хDК205/710

6,42±0,92

26,13±6,45

DК 205/710хDК293

6,65±0,71

43,56±4,95

DК 247хDК303/427

7,89±0,78

36,98±4,89

DК 303/427хDК247

8,46±0,81

25,23±4,49

DК 247хDК205/710

5,31±0,65

37,64±4,83

DК 205/710хDК247

5,72±0,67

37,15±4,70

DК 303/427хDК205/710

4,51±0,61

42,19±4,43

DК 205/710хDК303/427

6,83±0,74

46,79±4,96

 

r*

      r0,95**

 For   all the experiment

0,05

0,40

 For hybrids

0,33

0,44

 For inbred lines

-0,78

0,90

     1-data are shown as X±mt0.05* - Coefficient of pair correlation between frequency of matroclinal haploidy and degree of ear grainness, ** - critical value of coefficient of pair correlation at the 0,95 probability level.

      In general   frequency of matroclinal haploidy in the diallel set fluctuated from 0,59% to 11,12%.  Ear grainness after   pollination with ZMK-1   compared to free pollination was   reduced to 12,22-50,12%.  It could be suggested that such declination    was connected with the ability of   genotype to induce matroclinal haploidy.  However, in the given experiment   coefficients of pair correlations between the frequency of matroclinal haploidy and the degree of ear grainness in total for the experiment, separately for hybrids and separately for lines   were not significant. So, the existence of such a relationship is not confirmed.

     In the given diallel set parental forms were presented by inbred lines, multiple allelism is improbable, the data on the irregularity of meiotic chromosome disjunction are absent.   For the exclusion of few differences between reciprocal hybrids their mean values were taken to genetic analysis.

     For Òfrequency of matroclinal haploidyÓ the coefficient of regression  Wr/Vr was    b=0,88±0,11 (tb=7,70, t1-b=1,03, t0,05=3,20),  for Òdegree of  ear grainnessÓ it was     b = 0,98 ± 0,14 (tb = 6,83; t1-b = 0,16; t0,05 = 3,20).   The significance of regression coefficients for both traits and their non-significant deviation from 1 testified the absence of the effects of nonallelic interaction and dependent gene distribution in parental forms. Therefore, additive and dominant genetic system determines   the manifestation of two characters.

   The analysis of variance of a half of diallel table is represented in table 2.  

Table 2. The analysis of variance of  Òfrequency of matroclinal haploidyÓ and Òdegree of ear grainnessÓ in diallel crosses.

 

 Components of genetic variation

 Square sums

 Degrees of freedom

 Mean square

F fact.

F0,01

 ÒFrequency of matroclinal haploidyÓ 

a

0,6316

4

0,1579

65,93

4,22

b

0,1690

10

0,0169

7,04

3,17

b1

0,0373

1

0,0373

15,56

7,82

          b2

0,1011

4

0,0253

10,55

4,22

b3

0,0306

5

0,0061

2,55

3,90

R

0,0094

3

0,0031

1,31

4,72

Rt

0,0575

24

0,0024

 

 

ÒDegree of ear grainnessÓ  

a

1,2877

4

0,3219

19,05

4,22

b

2,9134

10

0,2913

17,24

3,17

b1

1,5816

1

1,5816

93,58

7,82

          b2

0,6934

4

0,1734

10,26

4,22

b3

0,6384

5

0,1276

7,55

3,90

R

0,0453

3

0,0151

0,89

4,72

Rt

0,4056

24

0,0169

 

 

 

     For both traits the significance of mean squares a and b testifies the effect of additivity and dominance. The significance of b1 proves that the effects of dominance are mainly concentrated in the same direction.  The significance of  b2 shows that dominant alleles are not dispersed among lines identically. Mean square a includes not only additive variance, but also a part of variance that is connected with dominant effects. Mean square  b3 is  not significant for Òfrequency of matroclinal haploidyÓ , so specific for every cross dominant effects which are not connected with  b1  and   b2   are not established.   Non-significant  R  means weak effect of the environment on the development of the characters.

     On the diagram of regression Wr/Vr for Òfrequency of matroclinal haploidyÓ the regression line intersects the positive part of axis Wr (fig.2), therefore, the middle degree of dominance for all the loci are incomplete, H1/D < 1.   Points of inbreds DК276-1, DК247, DК293 and DК303/427  are  located  nearer  to the  start of the regression line, they contain mainly dominant alleles  (from 75% to 100%), which are responsible for the decrease of Òfrequency of matroclinal haploidyÓ. For inbred DК205/710    ratio of dominant and recessive genes reaches the level 25% : 75%.  This inbred includes the biggest portion of recessive alleles, which determine the increasing of matroclanal haploidy.

 

 

Fig.2. Regression  for Òfrequency of matroclinal haploidyÓ  in maize (1 – 276-1, 2 – 247, 3 – 293, 4 – 303/427, 5 – 205/710).

 

     For Òdegree of ear grainnessÓ  the regression line  (fig.3)  passes through the  negative part of axis  Wr,  so the superdominance  plays the significant role in the manifestation of  this character, H1/D > 1. Dominant alleles are responsible for the decreasing, but recessive ones  - for the increasing of ear grainness.  The distribution   of dominant and recessive alleles is located within interval 75%: 25% for inbreds DК293 and DК303/427, for inbred DК276-1 it is near to 50%: 50%.   For inbreds DК205/710 and DК247   such distribution   approaches 25%: 75%.

 

 Fig.3. Regression  for Òdegree of ear grainnessÓ in maize (1 – 276-1, 2 – 247, 3 – 293, 4 – 303/427, 5 – 205/710).

 

The estimates of genetic parameters are represented in table 3.

Table 3. Genetic parameters for Òfrequency of matroclinal haploidyÓ  and Òdegree of  ear grainnessÓ.    

 Genetic parameters

 ÒFrequency of matroclinal haploidyÓ

ÒDegree of ear grainnessÓ 

D

0,03±9,54Е-05

0,04±0,0005

H1

0,02±0,0003

0,23±0,0012

H2

0,01±0,0002

0,20±0,0011

F

0,01±0,0002

0,02±0,0012

E

0,002±3,89Е-0,5

0,02±0,0002

H1/D

0,54

5,40

0,73

2,32

   ½

0,53

0,31

H2/4H1

0,18

0,21

Heritability in wide sense

0,85

0,82

Heritability in narrow sense

0,67

0,28

 

For Òfrequency of matroclinal haploidyÓ   incomplete dominance takes place (H1/D=0,54),   including separate loci (=0,73). For Òdegree of ear grainnessÓ  superdominance  is shown (H1/D=5,4), in that number  in every locus   (=2,3).

For the studied traits   the estimate of ½ differs from 1, the level of dominance varies in different loci. H1­H2, so dominant and recessive alleles are spread irregularly among parental inbreds. Positive estimate of F verifies the exceeding of the amount or effects of dominant alleles   over the recessive ones in the given set of lines and hybrids.

For the given characters the high values of heritability in wide sense proves the primary effect of genotypic variance in the development of the characters.  The significant   value of heritability in narrow sense for Òfrequency of matroclinal haploidyÓ    (0,67) confirms the significant role of additive gene effects and permits to make favourable prognosis   in phenotype selection     for high frequency of matroclinal haploidy.  It is important for production of testers, which are necessary in breeding programs of new   inducer genotypes.    The definite role of dominant effects in the development of  Òdegree of ear grainnessÓ   is indicated also by the considerable  difference  between the  heritability in wide sense (0,82) and the heritability in  narrow  sense (0,28).