Influência do cavalo sobre a fertilidade do polen no cavaleiro, em citrus

Influência do cavalo sobre a fertilidade do polen no cavaleiro, em citrus(^*)

F. G. Brieger; J. T. A. Gurgel(^**)

SUMMARY

1 - The object of the present paper is the study of the effect of different rootstocks on pollen fertility of the scion. The material was obtained from experiments by Moreira (18), in progress at the Experimental Station, Limeira, São Paulo, and from experiments by Vasconcelos (1), in progress in the Experimental Orchard at Piracicaba, São Paulo.

Homogeneity test of method

2 -A preliminary homogeneity test was carried out and showed that the methods for collecting and counting pollen were sufficiently satisfactory.

This test consisted in the following : pollen was collected from 3 plants for each of 5 different rootstocks, budded with laranja pera and for each plant 3 determinations were made. The decomposition of the total error showed no significant, large component (quadro I). Both error and means per plant or rootstock gave no signs of heterogeneity (quadros II and III). Finally the error of a binomial distribution around a mean of 40,19% and with an average of 145 pollen grains per determination, amounted to ± 3,23%, value pratically identical with that actually obtained (+ 4,07 in quadro I).

Experiments in Piracicaba

3 - The Experiment at Piracicaba included 3 commercial varieties of oranges : "Baía", "natal" and "coco", budded on five rootstocks (see quadros V and VII). The lay out of the experiment did not include any systhematic or random repetitions ; 10 plants of each combination were planted in one row each, as indicated in graph 1.

4 - The plants of "Baía" could not be included in the analysis since they did not contain any pollen. The determination of pollen fertility from the other two scions were subjected to an analysis of variance. In order to compensate for the lack of replications in the original lay out, 3 pollen counts were made for each individual plant, Thus the tota error could be divided into three parts : between rootstocks, between plants-within rootstocks, between determinations within plants (guadros IV and VI). Since in each of the two cases the last two components did not differ, they were united into one residual error "within rootstock".

No differences between pollen fertility caused by different rootstock, could be detected for "natal" (guadros IV and V), while in the case of "coco" (quadros VI and VII) there is some indication for sour orange (laranja azeda) of a slight reduction from ca 70% of normal grains to only 64%, with error standard for the latter mean of ± 2,38%.

Layout of experiment in Limeira

5 - The layout of the experiment at Limeira was much more complete and included four complete randon replications. Since part of the plots contained 4 individuals and others 9, the plots with 4 and 9 trees were planted separatly and their results were afterwards combined by confounding. The complete layout has been described by Moreira (18).

The experiment included again three commercial varieties namely : the grape-fruit "marsh seedless" and the sweet oranges "pera" and "Baía". Of these, "Baía" was completely male sterile, while the other two produced viable pollen.

6 - The analysis for each sub-bloc (or "quadra") consisted in a decomposition of the total error into four parts : between rootstocks, between repetitions, interaction rootstock-repetition and finally the residual error within plots. After confounding, one more component appears: between sub-blocs or quadras (quadros VIII and XI).

7 - The residual error was subjected to an homogeneity test. The individual errors "within repetition per rootstock" and their respective values d are given in the last columns of quadros IX and XII. In the first case all are insignificant, while in the latter there is a certain heterogeneity. There are three significant values of u, one larger and two smaller than 1, beside the very extreme value obtained for Poncirus trifoliata which, however, has to be treated separatly as we shall see later.

Orange "pera" Limeira

8 - The decomposition of the total error in each "quadra" or sub-bloc for "pera" gave the following results : There is a significantly high variation between rootstocks in sub-bloc A and a probably excessive variation between rootstocks in sub-bloc B. It seems that there is no difference between repetitions, except for a significant interaction in sub-bloc B. Since pratically all the components and especially the residual errors of the two sub-blocs are of the same order, the two sub-blocs were united and as result a new component appears: "between sub-blocs", which is highly significant. The significance of the errors "between rootstock" and also of the interaction remain unaltered (quadro VIII).

9 - Thus it may be concluded that the two sub-blocs are different and should not be united. Pollen fertility tends to be higher in sub-bloc B than A, with general means of 44,6% and 40,07% of viable pollen respectively (see also general and partial means in quadro IX).

10 - Five of the 6 values of t corresponding to the partial means of sub-blocs B (7th column in quadro IX) are relatively high, without being significant. Thus the appearance of one only possibly significant error "between rootstocks" is explained. On the other hand both extreme values of t for the partial means of sub-bloc A are definitely significant. There can be no doubt that the orange "pera" on sour orange has significantly more viable pollen grains, while "limão cravo" reduces the viability. In absolute values, these effects are not very pronounced. They amount only to differences of 5% from the general mean.

11 - It is most remarkable that the 12 rootstocks behave rather differently in repetitions. The error between repetition and per rootstock are also given in quadro IX and there appear four highly significant values. Actually a grouping seems to be more reasonable, uniting the four significant values of sERep with a mean value of ± 9,60% and 11 degrees of freedom. The first value, when compared with the residual error of + 4,51% is highly significant, while the latter is identical with it. One value has be left aside, being intermediate (± 6,28%) thus permitting an inclusion in both groups.

The fact that for some rootstock, the plots turn out to be heterogeneous and for others not, may be atributed to small soil patches which are known to exist in the experimental plots at Limeira.

Further more it may be seem from quadro X, that means per rootstock and repetition do not always show a parallel variation, thus explaining the appearance of a significant interaction in sub-bloc B.

Grape-fruit "Marsh-seedless" Limeira

12 - The results of this experiment seem much more complicated at first than those discussed above. All components per sub-bloc are significant, and the sub-blocs themselves are also different (first series of decompositions in quadro XI). But considering the means per rootstock (quadro XII) it is evident that the pollen fertility in Poncirus trifoliata is decidedly smaller than that in all other combinations. Thus, at first, Poncirus was excluded from the experiment (second series in quadro XI) and shall included again, but placed in contrast to the rest (least series in quadro XI). The difference between sub-blocs disappears now completely and we may accept the scheme of decomposition given in the lower right corner of the quadro XI as final. Here the three components : "between rootstocks", "between repetitions", and interaction are all significant and of the same magnitude.

13 - The general decomposition showed that Poncirus trifoliata occupies a special position. It causes a pronounced reduction in pollen fertility. For the remaining 11 rootstocks the analysis may be simplified since the two sub-blocs are not different anymore. The series of 11 partial means and the corresponding values of t form a continuous series with highly significant values at both extremes (quadro XII). Thus the effect of the rootstocks on pollen fertility of the scion is quite evident.

14 - As in the case of the "pera" orange, the different rootstock do not behave uniformly regarding to repetition. The individual values of aERep in quadro XII (3rd and 4th columns from right) may be classified into two groups : one with small error, around a balanced mean of + 10,05%. The former is not significantly different from the residual error, while the latter differs significantly. In one instance, orange "azeda-doce", a classification seems difficult. It is interesting that the two mean errors are pratically the same as obtained before in the corresponding analysis for "pera", while individual rootstocks do not show an identical behaviour in both cases.

This seems to reinforce still more our assumption that soil patches, distribuited at randon, cause these differences of errors between repetitions.

15 - The significant interaction is caused by the irregular behaviour of the partial means of rootstock and repetition, given in quadro XIII.

16 - Since the percentage values obtained are relatively near the limit of O, Fisher's angular transformation was applied (quadros XIV and XVI), but the results obtained did not offer any new results.

Residual and theoretical errors

17 - In order to analyse still further homogeneity of methods and to see if decomposition removes all systhematical variations, leaving variations due to chance only, comparison was made between residual error and theoretical error calculated by the formula:

σi = ± √⁼v%(100-⁼v%)/n

where n stands for the mean number of pollen grains per slide counted ; v% for the mean percentage of viable grains.

Generally speaking the residual errors are significantly larger than the theoretical values, while in one case u is even significantly smaller than 1. Considering that the number of grains counted per slide was very variable, we may be satisfied with the two corresponding values for the error (observed and ideal) which are always of about the same order.

Results

The results may be finally summarized as follows :

a) The method used was satisfatory.

b) The fertility of the pollen of the scion is to some extent influenced by the heterogeneity in the plots.

c) The rootstocks have definitely a pronounced effect upon pollen fertility of the scion.

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AGRADECIMENTOS

É justo que deixemos aquí registados agradecimentos sinceros aos nossos colegas G. Ó. N. Addison e Nahum Klein, pela valiosa ajuda nas contagens do polen, e ao sr. Eduardo Rodrigues A., pelo auxílio nos cálculos estatísticos.

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(*

) Os estudos aqui apresentados fazem parte da análise pormenorizada de uma experiência sobre a influência de cavalo e cavaleiro para

Citrus, em andamento na Estação Experimental de Limeira

(18); posteriormente foi incluida uma experiência, também sobre o mesmo assunto, efetuada em Piracicaba (1).

(**

) Cadeira de Genética da Escola Superior de Agricultura "Luiz de Queiroz" da Universidade de São Paulo, Piracicaba

Datas de Publicação

• Publicação nesta coleção
  05 Jul 2010
• Data do Fascículo
  Dez 1941