Morphological characters variability of male gametophyte of waxy maize regenerants --Kravchenko, OA, Palii, AF, Kravchenko, AN, Lysikov, VN In our investigation the 346 and 502 inbred lines and their waxy counterparts, as well as their R1, MR1, MR2 progeny, were taken as the experimental material. For the analysis in the light scanning microscope "Morphoquant" permanent preparations of mature pollen were made using the technique developed by Kravchenko A.N. (In: Recombinogenesis in Evolution and Breeding, Kishinev, p.264-265). Such characters as perimeter (µm), area (µm2), form factor (relative units), width (µm), diameter (µm), eccentricity (relative units) of pollen grain, as well as those of vegetative and generative cell nuclei were evaluated. The data were processed by two factor analysis of variance.

The results obtained indicate that morphological characters of pollen grain of the 346 and 502 inbred lines and their counterparts varied insignificantly (coefficient of variation (V)<10%). However, the variability range of such pollen grain characters as perimeter, area, and eccentricity in R1, MR1, and MR2 generations was significant (V>20%). In addition, the higher coefficients of variation were noted for waxy counterparts.

Analysis of variance revealed that variability of pollen grain characters studied was either genotype or gamma radiation dependent (Table 1).

Table 1. Share of variability of pollen grain characters, %.
 
characters
determined by:
  genotype gamma radiation their interaction
perimeter 65.7*** 11.36*** 14.11***
area 53.46*** 30.65*** -
form factor 9.78* 17.39*** 55.18***
diameter  66.73*** - -
width 39.32*** 49.27*** 4.63*
eccentricity 15.78*** 63.83*** 11.24***

*** - P<0.001; * - P<0.05

However, the variability of width and eccentricity was to a large degree gamma radiation dependent. It is worth noting that variability of such a character as form factor proved to be mostly determined by the interaction of factors studied. For waxy counterparts the average values of such characters of pollen grain as perimeter, area, and eccentricity were found to be higher (Table 2).

Table 2. The average values of morphological characters of pollen grain.
 
 
Characters
Genotype perimeter  area form factor diameter width eccentricity
346+/+ 299.16 5178.18 16.11 86.46 72.92 1.173
346wx1wx1 307.69 4935.07 17.98 83.33 71.42 1.360
502+/+ 281.37 4447.43 17.93 80.51 67.92 1.206
502wx1wx1 289.99 4685.95 19.95 83.46 67.85 1.340
Least significant difference (LSD 0.001 ) 7.04 237.28 1.63 2.73 1.93 0.16

In generations of regenerants derived from inbred lines studied the average values of perimeter, form factor, and eccentricity proved to be decreasing in comparison with control (Table 3).

Table 3. Pollen grain morphological characters variability in generations of regenerants.
 
 
Characters
Generation perimeter area  form factor width eccentricity
Control 304.25 4816.16 18.37 68.62 1.22
R1 296.89 4340.32 17.96 66.79 1.2
MR1 289.66 4546.81 17.55 67.96 1.21
MR2 282.99 5166.75 17.12 73.51 1.15
LSD 0.001 6.1 205.49 0.41 1.67 0.11

It was also found that morphological character variability of vegetative and generative cell nuclei in MR1 and MR2 generations was higher (14%<V<47%) in comparison with control and R1 generation. Analysis of variance showed the reliable dependence of variability of these characters on genotype, gamma radiation and their interaction. It should also be noted that the variability of characters studied (except eccentricity of generative cell nuclei) was more gamma radiation dependent (Table 4).

Table 4. Morphological character variability of vegetative (V) and generative (G) cell nuclei of pollen.
 
  the share of variability determined by:
Characters genotype gamma radiation their interaction
Perimeter V 39.79*** 43.32*** 11.98***
Area V 40.91*** 42.19*** 11.75***
Form factor V 35.99*** 51.68*** 4.89*
Diameter V 35.77*** 53.26*** 5.79**
Width V 29.39*** 35.17*** -
Eccentricity V - - 56.71***
Perimeter G 30.01*** 61.52*** 5.21***
Area G 26.68*** 49.35*** 10.58**
Form factor G 9.44*** 77.68*** 5.46*
Diameter G 7.51** 80.69*** -
Width G 6.4*** 81.93*** 7.06***
Eccentricity G 37.28*** 35.36*** -

p<0.05; **p<0.01; ***p<0.001

The average values of such characters as perimeter, width of vegetative cell nucleus and all morphological characters of generative cell nucleus were found to be decreasing for regenerants of waxy counterparts (Table 5).

Table 5. The average values of morphological characters of vegetative (V) and generative (G) cell nuclei in dependence of genotype.
 
 
Genotype
Characters 346+/+ 346wx1wx1 502+/+ 502wx1wx1 LSD 0.001
Perimeter V 43.62 40.33 39.29 37.06 1.74
Area V 92.00 78.24 78.81 69.73 5.92
Form factor V 21.88 19.69 16.18 17.93 1.73
Diameter V 12.25 10.78 8.1 9.62 1.42
Width V 8.71 7.42 8.0 7.4 1.2
Perimeter G 22.00 20.31 22.31 17.58 1.29
Area G 17.24 15.76 18.12 12.39 3.24
Form factor G 26.68 23.31 22.03 18.48 3.18
Diameter G 7.63 5.98 6.27 4.69 1.54
Width G 1.34 1.01 1.73 1.41 0.3
Eccentricity G 3.76 3.2 3..86 2.93 0.54

In MR1 and MR2 generations the average values of characters studied proved to be increasing in comparison with control and R1 generation. In addition the plants of MR2 generation had the highest average values of male gametophyte characters studied (Table 6).

Table 6. Morphological character variability of vegetative (V) and generative (G) cell nuclei of pollen among plants of different generations.
 
 
Generation
Character Control R1 MR1 MR2 LSD 0.001
Perimeter V 36.96 38.51 40.27 42.99 1.5
Area V 69.02 75.37 81.5 88.58 5.13
Form factor V 15.85 17.39 18.96 21.15 1.5
Diameter V 7.15 8.52 9.79 12.48 1.23
Width V 7.24 7.99 9.06 10.65 1.04
Perimeter G 18.35 19.5 20.97 24.33 1.12
Area G 13.66 14.92 15.89 20.07 2.8
Form factor G 19.49 20.89 22.34 31.02 2.76
Diameter G 3.71 5.09 6.7 8.95 1.33
Width G 0.43 1.88 3.26 4.47 1.15
Eccentricity G 3.25 3.49 3.72 3.99 0.17

In general, according to the results obtained the pollen of regenerants and their progeny (especially those derived from irradiated embryos) was found to differ from the male gametophyte of inbred lines by the range of morphological characters studied.
 
 


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