Dependence of some characters of the maize male gametophyte on gamma radiation and genotype
--Kravchenko, OA

The aim of the present study was to find out whether genotype and gamma radiation affect pollen morphological and cytochemical characters. For this purpose dry seeds of inbred line 346 and its waxy counterpart were irradiated (100 Gr) before sowing. For analysis in the light scanning microscope "Morphoquant" permanent preparations of mature pollen were made using a technique developed by Kravchenko A.N. (In: Recombinogenesis in Evolution and Breeding, Kishinev, p.264-265, 1986). Such characters as area, perimeter, eccentricity (the ratio of the biggest diameter to the smallest one), DNA quantity (in relative units) and chromatin dispersity of vegetative and generative cell nuclei were evaluated. The data were processed by two factor analysis of variance which revealed some interesting results.

Morphological characters of vegetative cell nuclei were mostly genotype-dependent and the presence of the wx1 gene resulted in decreasing of area, perimeter, and eccentricity (Table 1). The same characters of generative cell nuclei as well as DNA quantity of vegetative cell nuclei were affected by gamma radiation factor. It should also be noted that variations with gamma ray treatment had higher indices of these characters (Table 2). DNA quantity and chromatin dispersity of generative cell nuclei proved also to be influenced by factors studied. In such a case the waxy counterpart had higher indices of these characters, in particular, chromatin dispersity was 1.5 as much. The values of cytochemical characters of generative cell nuclei affected by gamma radiation were also found to be increased. Thus, these data indicate that the effect of gamma radiation and genotype was reliable and contributed to variability of male gametophyte morphological and cytochemical characters.

Table 1. Variability of morphological and cytochemical characters in dependence of genotype.
 
  +/+ wx1/wx1
  vegetative cell nuclei  
PERIM 40.79* 39.23*
AREA 83.58** 75.49**
EXT 1.46** 1.39**
SDENS 11.90 11.11
DISP 2.66** 3.33**
  generative cell nuclei  
PERIM 19.41 18.59
AREA 14.02 13.81
EXT 3.51 2.99
SDENS 3.25*** 3.68***
DISP 14.23** 21.92**
*p<0.05, **p<0.01, ***p<0.001

Table 2. Effect of gamma radiation on morphological and cytochemical characters of male gametophyte.
 
  control 100 Gr
  vegetative cell nuclei  
PERIM 38.7*** 41.3***
AREA 75.0** 84.0**
EXT 1.43 1.43
SDENS 11.00* 12.0*
DISP 2.83 3.15
  generative cell nuclei  
PERIM 18.37** 19.63**
AREA 12.84** 14.98**
EXT 3.32 3.36
SDENS 3.31** 3.62**
DISP 16.75** 19.39**
*p<0.05, **p<0.01, ***p<0.001

Abbreviations: PERIM - perimeter, AREA - area, EXT - eccentricity, SDENS - DNA quantity, DISP - chromatin dispersity


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