At the same time that perennial teosinte is being used in wild germplasm introgression projects in maize, we have also obtained a diploperennial teosinte (Zea diploperennis) introgressed population of maize. As was previously pointed out (MNL 60:82 and MNL 61:65), this population was originated from the recombination of different maize stocks with diploperennial teosinte germplasm given by interspecific hybrids. A recurrent selection cycle was started from the introgressed population, as was done when we used perennial teosinte (see preceding), with the only purpose of making the developed individuals capable for practical purposes.
Table 1. Relevant traits of S1 lines derived from a maize population
introgressed with diploperennial teosinte.
|Character||Mean ± SD||Range|
|Days to tassel||68.9 ± 3.2||63-77|
|Days to pollen||79.0 ± 3.6||68-86|
|Days to silking||75.4 ± 3.8||66-83|
|Protoandrous (days)||-3.6 ± 0.2||-2-(-5)|
|Plant height (m)||185.9 ± 17.1||145-215|
|Ear insertion height (cm)||91.2 ± 15.8||55-120|
|Number of tillers||2.1 ± 0.6||1-4.4|
|Number of ears per plant||2.7 ± 0.5||2-4|
|Ear lenght (m)||12.1 ± 1.8||8.5-15.7|
|Ear diameter (m)||2.7 ± 0.4||1.9-3.5|
|Ear weight (g)||44.9 ± 20.8||25-100|
|Number of kernel rows||10.0 ± 1.7||8-14|
|Weight of 50 kernels (g)||8.6 ± 2.1||5-14.2|
A preliminary evaluation of S1 derived lines from self-pollinated plants of the original population is summarized in Table 1. There is considerable variation in most of the traits we have measured, but this is smaller than that shown by the original population (see MNL 61:65). When these lines are compared with those derived from the perennial teosinte introgressed population, it can be deduced that they have more tillers with a higher number of ears per plant, though these ears are smaller in size.
Generally a smaller variation is noted in this case than in the previous one, though it can be considered that there is a wide germplasm and genetic base produced by the introgression of foreign germplasm in maize. As in the case of S1 derived lines from the perennial teosinte introgressed population, those derived from a diploperennial teosinte introgressed population show a lower number of tillers and ears per plant than the original population from which they arise.
The results we have obtained do not let us deduce that perennial teosinte germplasm introgression in maize is more successful than diploperennial teosinte germplasm introgression. But we must say that this comparison is not possible, as we have not used the same maize stocks as recurrent parent. Especially as in the case of introgression with diploperennial teosinte germplasm, the genetic base of the maize stock used was really very narrow.
The results obtained let us deduce that the utilization of germplasm belonging to two of the most phylogenetically distant taxa of Zea, from the cultivated species (maize), produces a great variability, probably similar to the variability found by primitive man from whom modern maize is derived. If this is true now, then man once more has the possibility of leading the evolution of maize to more productive forms (another plant architecture?) through less empirical methods.
Gabriela Pischedda and Jorge L. Magoja
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