DNIEPROPETROVSK, UKRAINE
Institute of Grain Farm, UAAS

Effect of metholachlor on pollen germination of different maize genotypes
--Satarova, TN

The inclusion of microgametophyte selection in breeding programs can greatly improve the process of the creation of the initial material of maize. It is determined by such characteristics of the male gametophyte as small size, a great number of pollen grains, the possibility of analyzing without damage to the maternal organism, and also by the data on the expression of a part of sporophyte genes in the period of the gametophyte's existence. Investigations on maize gametophyte selection confirm the efficiency of such an approach. The estimation of genotypes involved in pollen tolerance to different environment factors also requires attention because the ability to form a sufficient amount of pollen, the viability of the male gametophyte and other characteristics are important breeding characters. The elaboration of the details of microgametophyte selection will permit carrying out such selection in the prospective populations at the early stages of the breeding process.

We investigated the ability of pollen grains of 5 different lines of maize to germinate on artificial nutrient medium with the herbicide metholachlor=2-ethyl-6-methyl-N-(1-methyl-2-methoxi-ethyl)-chloracetanilide (commercial mark - dual 960EC). Pollen was taken from field plants which were isolated at the beginning of flowering. The control germination medium included 150 g/l sucrose, 300 g/l calcium chloride, 100 mg/l boric acid and 6 g/l agar. The germination was carried out at a temperature of 26-28 C. The control medium was added accordingly with 10 mg/l, 50 mg/l, 100 mg/l and 500 mg/l metholachlor. The data are shown in the table.

First of all it is necessary to remark that different genotypes differ on the percentage of pollen grain germination in control. The greatest percentage was obtained for line 751, the others did not have a very high percentage of germination, which could be connected with genotypical peculiarities and also, maybe, with the specific reaction of genotypes on the weather conditions of the year.

Table. Effect of herbicide metholachlor on the germination of maize pollen grains in vitro.
 
Metholachlor mg/l Percentage of pollen grains germinated
  751 GK26 1620 DK427/501 DK4/217
0 54.78 13.22 11.50 9.83 7.75
10 42.63*** 12.33 16.50* 13.17 11.63**
50 10.38*** 3.78*** 4.17*** 2.33** 1.56***
100 0*** 0.44*** 0.83*** 0.17*** 0***
500 0*** 0*** - - -
*, **, *** - differences from control are significant at P<0.05, P<0.01 and P<0.001 accordingly.

For line 751, which had the highest percentage of germination in the control (54.78%), all concentrations of metholachlor significantly reduced the percentage of pollen germination. For line GK26, where the percentaage of germination in the control was 13.22, inhibition was observed from the concentration of 50 mg/l metholachlor. For other genotypes with a lower percentage of germination in the control the concentration 10 mg/l had a stimulating effect and a significant decline was obtained at the metholachlor concentration of 50 mg/l. A fall in the percentage of pollen germination together, 63.74-81.05% for concentration 50 mg/l and 92.78-100% for concentration 100 mg/l was found. However, not all genotypes decreased the percentage of pollen germination at the same rate. The least decreases, 63.74% and 92.78% for the two above mentioned concentrations were observed for line 1620 and the greatest, 81.05% and 100% for line 751.


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