Pollen germination influenced by genotype and/or agrichemicals

We reported (MNL 54:66) a pollen bioassay for agricultural chemicals and extended the use of this bioassay during the 1980 field season. A total of 48 genotypes were examined: (i) thirteen inbred lines were tested with all ten chemicals (MNL 54:66) in three concentrations; (ii) pollen from a further fifteen inbreds and twenty plant x plant reciprocal crosses was challenged with a selection of these chemicals. Oh43 was used as an hourly control for germination and tube elongation measurements. Forty-eight treatments/controls, each in triplicate with five samples per replicate, were scored daily. We report below preliminary results involving ten inbreds, two reciprocal crosses and seven agrichemicals (Tables 1 and 2). Percent germination for individual genotypes was calculated and averaged for all chemical treatments. These were then standardized to the control levels (Table 1). All genotypes germinated poorly at the field dose (manufacturer's recommendation for the sporophyte) level of the chemicals, while germination at the tenfold dilution was generally only slightly below the control level. Several genotypes demonstrated enhanced germination at the hundredfold dilution. The largest dose-responses were recorded for genotypes Oh43, F7 and A619 whereas CM48 and W23 appeared to be very sensitive to chemical treatment even at the hundredfold dilution. The reciprocals F7/Oh43 and Oh43/F7 were tolerant of all chemical treatments although some differential cytoplasmic effect was exhibited.

Table 1. Standardized mean germination of individual genotypes (21 chemical treatments)
 
Genotype Control (no treatment) FD x 10-2 FD x 10-1 FD*
CM48 1.0 0.6 0.1 0
Co220 1.0 1.2 1.0 0.5
F7 1.0 1.3 0.8 0.3
F2 1.0 1.1 0.7 0.2
W64A 1.0 0.9 0.5 0.1
A619 1.0 1.4 0.8 0.4
Oh43 1.0 1.7 1.1 0.4
A158 1.0 1.1 0.9 0.4
W401 1.0 0.9 1.1 0.6
A654 1.0 0.9 0.9 0.7
W23 1.0 0.4 0.3 0.1
F7/Oh43 1.0 1.2 1.0 0.8
Oh43/F7 1.0 0.7 0.7 0.8

*FD = Manufacturer's recommended field dose.

Mean percents germination of all 13 genotypes were standardized and grouped according to the chemicals tested (Table 2). In all cases, the control level of germination was less than that of the hundredfold dilution. Germination at the field dose approached 0 in all but three cases.

Table 2. Standardized mean germination (13 genotypes)
 
Chemical Control (no treatment) FD x 10-2 FD x 10-1 FD*
Atrazine 1.0 1.0 0.7 0
Banvel 1.0 1.3 1.1 0.9
Basudin 1.0 1.1 1.3 0.3
2,4-D 1.0 1.2 0.7 0
Lannate 1.0 1.1 1.0 1.0
Malathion 1.0 1.3 0.1 0
Roundup 1.0 1.1 0.1 0

*FD = Manufacturer's recommended field dose.

Dose response curves for all genotypes and chemicals have been constructed. Pronounced dose responses are stimulated by the chemicals Malathion, Roundup, 2,4-D and Atrazine with the field dose resulting in complete inhibition of germination. No genotype showed a dose response to the insecticide Lannate or the herbicide Banvel.

Further biometrical analysis of these and the remaining data are under way.

K. A. Startek and D. B. Walden

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

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