Genetics of environmental resistance and super-genes: Latente aluminum tolerance

In MNL 56:30-32 the authors suggested that environmental resistance, in Levitt's sense and in general, followed R1 and B, the two major super-genes that control anthocyanin color distribution in plant parts. Supporting data were presented for heat tolerance in seeds. Now we present some data for aluminum tolerance. The same flint Cateto line, C1, and the same original MNL marker stock, g R sr2, were used. The F2 seeds of the cross were germinated in moist rolled paper towels, and four-day-old seedlings were transferred to acrylic plates and grown in a modified nutrient solution of P.R. Furlani and R. B. Clark (Agron. J. 73:587-594) containing 3.0, 3.5, 4.0 or 4.5 mg Al per liter. After a week the plants were evaluated for Al resistance by visual ratings of Al toxicity symptoms on roots. Each unreplicated experiment, since the segregation was 0.5625 R:0.4375 r, consisted of 28 R colored seeds and 22 r uncolored seeds. With n=187 there were 46 Lte R, 54 Lte r, 55 lte R and 32 lte r seedlings. The deviation from 9 Lte:7 lte is X2=0.58 with 0.5>P>0.3, non significant, with the X2 for interaction Lte x R=5.55*, significant at P<0.05. The value of p for Lte R estimated by maximum likelihood is negative, indicating a linkage value greater than possible by reality. After the roots were classified for resistance and susceptibility to aluminum, the seedlings were transplanted to a field nursery in four separate rows. These seedlings transplanted to the field nursery reduced to n=154 at flowering time. At flowering time they were further classified for g and sr2. Since the marker is b and the C1 line is B-b, a classification for this factor was also done. This last reading has a lower number than the former because many plants did not emit tassels and could not be classified for this character. This reading gave 58 Lte B-b, 24 Lte b, 36 lte B-b and 16 lte b. The X2 deviation from 9 Lte to 7 lte is 1.38, from 3 B-b:1 b 1.68 and the interaction Lte x B-b 0.03, all non-significant values. But the value p=28+10.0 calculated by maximum likelihood is significant. The data with chromosome 10 markers are presented in Table 1. Since no detectable difference was seen among aluminum levels, only totals are presented. The ratio of resistant to susceptible plants gave an almost perfect fit to 9:7. The interaction X2 value for Lte x g was 13.01**, indicating linkage, while the R Lte and g R interactions were not significant. Thus, one of the Lte genes is between g and R1, the other being near B. Since sr2 had a high mortality of its own, it is useless for the analysis. As shown in Table 2, all p values were calculated by maximum likelihood and by the product moment method. The three tightest values were transformed to centimorgans, and these latter values utilized to get more precise values by differences, as illustrated in the preceding article. These values were adjusted to the known distance between g and R. The most probable position of latente-2 is two units from R.

Transforming the p value obtained for B-b Lte1 to centimorgans leads to 33.0 cM and multiplying by the correction factor from Latente-2 (14 divided by 24) leads finally to 19.2 units from B-b. H. G. Nass and P. L. Crane (Crop Sci. 139-140), studying nine endosperm types, concluded that fl1 may have an advantage under stress conditions. It could well be that it was to a factor linked to fl1. Also in one of our Tuxpeno materials in which fl1 was transferred by several backcrosses to a fl1 marker originally from Pennsylvania, USA, we found an unusual tolerance to heat by our stronger rapid aging seed test. So the most probable position of Lte1 is 19 units from B and in the direction of fl1, that is in position 68. It must be between B and fl1.

In the next article we present data obtained with tolerance to heat which will permit a much greater precision of the estimates of p with Latente-2.

Table 1.

Table 2.

L. T. de Miranda, P. R. Furlani, L. E. C. de Miranda and E. Sawazaki


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