It has been a general experience of the maize breeders that the trait, number of leaves per plant of a given genotype, remains either uninfluenced or influenced only to a minor extent by environmental factors. The late maturing maize types, however, have been observed to bear more leaves than those maturing early (S. S. Chase and D. K. Nanda, 1967, Crop Sci. 7:431-432; J. R. Allen et al., 1973, Agron. J. 65:233-235). It has been another experience of the breeders that the opaque-2 maize matures later than the analogous normal maize. An experiment was thus conducted to study if the o2 converted maize genotypes have more leaves on the main stalk than their normal analogues. The experiment comprised 6 o2 converted parental inbred lines, all possible 15 single cross hybrids, 60 three-way cross hybrids, 45 double cross hybrids and all the corresponding normal analogues. The trials were conducted at one location for two years in a split plot design. The results on total leaves per plant including those destroyed early in development (assured by marking the 10th leaf at 12-13 leaf stage), observed on five competitive plants in each row have been presented for each of the two years in Table 1.
It will be seen in the table that there were somewhat fewer leaves per plant in almost all the genotype groups in the wetter and cooler year 1974 than in the year 1973. This difference was, however, limited, on average, to only one leaf per plant.
It may be pointed out that the analyses of variance of these data showed a significant difference only between the various genotype groups, during the year 1973. The variance due to the opacity factors was not significant in either year. Hence it is concluded from the above data that the presence or absence of the o2 gene in the recessive homozygous condition has no influence on the number of leaves per plant, which is otherwise a relatively constant feature of a given genotype. This trait does not seem thus to be a reliable index of maturity in the case of o2 maize, since it has been observed that this genotype had 5.7% more relative grain moisture at harvest in the o2 recessive homozygotes than in their normal analogues (unpublished data). This difference was statistically significant.
D. Gupta* and I. Kovács
*Present address: Geneticist, Central Potato
Research Institute, Simla 171001, India
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