Izvorni znanstveni članak
Leaf and Flower Deformations of Datura stramonium L. Infected With the Cucumber Mosaic Virus
Nikola Juretić
; Hrvatska
Sažetak
Some plant viruses do not cause only alterations of vegetative organs but also deformations of flowers and fruit. The changes of flowers can be developed in different ways, for example as reduction, deformations, antholysis etc. The last term indicates all intermediate stages between a normal flower and an entirely vegetative leafy branch (Bos 1963).
Today a great number of viruses are known that cause anomalies of reproductive organs of their hosts (Palm 1933; Michailowa 1936; Valent a 1958, 1961; Bos 1963; Miličić 1964). Although deformations of generative organs are not a rare phenomenon, they are nevertheless less frequently described in relation to deformations of vegetative organs. For example it is known that the cucumber mosaic virus (CMV) causes alterations of leaf on many hosts, but only few facts about deformations of reproductive organs under the influence of CMV have been described.
Some strains of CMV cause severe alterations even on Datura stramonium. The type strain of CMV produces only colour deviations in leaves (Smith 1957). The strains investigated by Hein (1957) and Delević (1963) produce similar symptoms. According to Kovacevski (1965) many strains of CMV in Bulgaria do not cause symptoms on Datura. However, Lovisolo and Benetti i (1961) in Italy have described the so-called “alloiophylly” strain which produces strong mosaic symptoms and deformations of leaves on Datura stramonium. Many isolates from Bulgaria and Rumania also cause deformations of leaves and moreover, alterations of flowers and fruit (Kovacevski 1965). Aubert (1960) also reported that CMV produces anomalies of leaf and severe deformations of flowers and fruit (spiralisation of flowers, disorganization of corolla, partial or entire suppresion of spines on the capsules). These data, Aubert’s and Kovačevski’s, are the only facts wich we have found in the literature about the anomalies on reproductive organs of Datura stramonium.
In this paper we shall describe our investigations of five strains of CMV that all cause deformations of Datura stramonium leaves. Besides that four of these five strains produce anomalies of flower and fruit. Because Aubert (1960) and Kovačevski (1965) have not described these deformations of flowers and fruit of Datura stramonium in detail we shall do it here.
We have experimented with the following strains: Bll, B12, B13, B14 and B15. The strains B12 and B14 are come from Yugoslavia; they were undetermined at the beginning of the research. Strain B12 is isolated from infected tomato plant cultivated in field near Zagreb, strain B14 from a plant from the Botanical garden of Zagreb University. Both strains belong to the green strains of CMV. Strain Bll, also a green strain of CMV, has been obtained from the Institute for Phytopathology of Halle University. Strain B13, a white strain of CMV, came from England. This strain we have obtained by kindness of Dr. K. Schmelzer from the Institute for Phytopathology Aschersleben (East Germany). Strain B15, which we have got by kindness of Dr O. B o d e (Biologische Bundesan- stalt Braunschweig, West Germany), is a yellow strain from USA. The isolates from Yugoslavia (B12, B14) have been identified first by the reactions on the test plants.
The studied strains were transmitted by means of mechanical inoculation to differential host plants. The list of the host plants is on table 1. From five strains which we have investigated four strains (Bll, B12, B13, B15) can cause deformations on the reproductive organs of Datura. We were able to observe that strain B15 produces deformations on Physalis peruviana var. pubescens as well (pi. 5, n; pi. 6, s, t). The alterations on the reproductive organs of the other tested plants have not been observed.
Besides, on basis of the comparison of test plants symptoms which cause our undetermined isolates B12 and B14 on the one hand, and the exactly determined strains Bll, B13 and B15 on the other hand, we have identified our isolates also by the cross-protection test. In the last experiments we have used the “white” strain B13 and the “yellow” strain B15.
The cross-protection test was performed with 30 Nicotiana tabacum var. “Hicks resistant” plants. As no tobacco plant that was infected first with the green isolate B12, and then superinoculated with the yellow CMV strain B15, had developed the yellow mottling, it was unambignously demonstrated that isolate B12 protects the test plant from an additional infection with the yellow strain.
The cross-protection test with the isolate B14 was performed in the same manner as with the isolate B12. In this test also the tobacco plants, that were first infected with the green isolates B14, were immune against the additional infection with the yellow strain B15.
The cross-protection test with the strain B12 was performed yet in another manner, that is by making use of the “white” starin B13 and Nicotiana megalosiphon. The green isolate B12 causes a mottling on Nicotiana megalosiphon, whereas the white strain B13 produces necrotic spots on the inoculated leaves of this plant. These differences make it possible to establish whether the isolate B12 protects Nicotiana megalosiphon from an additional infection with the strain B13 or not. After superinoculation with B13 we have not observed any necrotic spots on the leaves of Nicotiana megalosiphon.
By these tests it was clearly proved that our strains B12 and B14 belong to CMV. The results of the investigations of physical properties, which are presented on table 2, also confirm this conclusion.
All the five strains of the CMV produce very intense alterations on Datura stramonium leaves. These symptoms are similar to the ones described by Lovisolo and Benetti (1961), and Kovačevski (1965). The symptoms are the following: mottling, curving of the margins of leaves upwards, roughness of the surface, prolongation of the lamina tips, shortening of the leaf, reduction of lamina parts etc. These alterations are presented on pi. 1 — 3. We stress that strain B14 causes relatively minute changes on the leaves of the Datura stramonium. Strains Bll and B12 produce more intense alterations and they are nearly identical. The yellow strain B15 and the white strain B13 cause the most intese deformations on the leaves. These strains are different from the green ones in that they can cause shoe-string leaf (pl. 2, b, c, e; pl. 3, d).
From the five strains which we have transmitted to Datura stramonium, four strains cause deformations on flower and fruit; only strain B14 does not produce anomalies of the reproductive organs.
We shall easily notice the variability and the depth of flower and fruit alterations if we compare the ill flowers and fruit with the healthy ones. Pl. 4, d represents the normal flower in an early stage of development. An older flower can be seen on pl. 4, e, and a completely developed flower on pl. 4, a—c. The completely developed flower is about 7 cm long and it is composed of five sepals and petals grown together and also from five stamens. The ovary is composed of two carpels (pl. 8, a, b; pl. 11, j, k). The single parts of a normal flower are presented also on pi. 6, a, l; pi. 7, a; pl. 11, a, b. As the flower symptoms caused by strains Bll and B12 on the one hand and by strains B13 and B15 on the other hand are very similar we shall describe only the anomalies caused by the green strain B12 and the yellow strain Bio. Alterations on infected flowers and fruits are represented on pl. 4 — 13. When Datura stramonium plants are infected early, that is in a stage with three to four leaves, almost all flowers have an abnormal development. The most obvious anomalies are shortening of flower, and severe alterations of calyx, corolla and pistil.
The anomalous calyx shows apart from considerable shortening (pl. 4, k; pl. 6, c, h, i) also other abnormalities. Sometimes, for instance under the influence of both strains the calyx remains permanently closed while in normal flowers it opens at the top and it lets the other flower parts pass out (pl. 4, i; pl. 5 d). The cross section of the normal calyx shows that it has the form of an irregular pentangle (pl. 6, d). The abnormal calyx has also the form of an irregular pentangle (pl. 6, e) but its sides are not concave as in the normal calyx but they are convex.
In order to be able to study the calyx parts more easily we have separated it from the flower in the place where it is attached 1» the receptacle, and then we have cut it lengthwise and opened it (pl. 6, a — c, f-k).
Strains B12 and B15 cause the parts of the calyx to become of different length (pl. 4, k; pl. 6, i). The calyx can be split in one place or in several places on its margins, with shorter or deeper incisions, which sometimes can reach the basis of the calyx (pl. 4, m; pl. 12, d, i). Moreover, the calyx can be completely stunded in one or mor places of its normal extent so that it does not anymore have the shape of a tube which surrounds other flower parts (pl. 6, o; pl. 5, e). In some cases, the calyx can be developed only in one little part of its normal extent so that it becomes scale-like (pl. 6, g\ pl. 12, i).
The anomalous calyx can often be broader than the normal one; in that case it does not lean against the corolla closely (pl. 4, l, m; pl. 12, d right, j). Such a broad calyx can be also deeply incised (pl. 4, I).
While the normal calyx has five longitudinal “ribs”, more or fewer than five of them can be developed on the deformed calyx. The “ribs” can disappear in some cases entirely (pl. 4, /; pi. 6, k; pl. 12, d), and the cross section of the calyx has the form of a regular circle. On a deformed calyx the numebr of tips may be greater or smaller than five (pl. 6. c, h, i). The stunted calyx can in both strains be completely or partially grown together with the corolla (pl. 12, g). Sometimes strain B12 causes outgrowths, that is enations on the infected calyx (pl. 4, h). The surface of the deformed calyx is usually rough, and the parts of the stunted calyx are easily broken.
The corolla as well as calyx are shortened under the influence of both strains. The deformed corolla has often the length from 2 to 5 cm instead of 7 cm. The anomalous corollas in their lower parts are broader than the normal ones (pl. 6, l — o). While the normal corollas are snow-white, the deformed ones can be green.
The anomalous shape of corolla has been studied just as the calyx. We have separated the corolla from the other flower parts and then we have cut it lengthwise and opened it (pl. 6, l—r).
Short or deep incisions can arise along the corollas. Mostly, only one lateral split, which does not reach the basis of the corolla can be formed. Trough the split on the corolla we can see the internal parts of the flower (pl. 4, g, j — l; pl. 5, b — e; pl. 6, q, r; pl. 12, e — h). Both strains B12 and B15 cause also deformations at the top of the corolla. While the normal corollas finish with five short tips at the top, the abnormal ones finish with longer tips or theread-like appendages (pl. 4, a—c, k; pl. 5, a; pl. 6, m, o, p; pl. 12, /, g). The appendages are often curved and can interweave. On account of that the corolla is closed at the top (pl. 4, j, l). Under the influence of strain B15 the parts of the corolla can grow together with the stigma of the pistil. Strain B12 can cause enations on the corolla (pl. 4, g; pl. 12, a, b).
Strains B12 and B15 produce also deformations on the stamens, specially shortening of filaments, that are about 6 cm long in normal plants. Because of the considerable shortening of filaments, the stamens can become only several mm long (pl. 4, k; pl. 5, e). The infected flowers usually have also a greater number of stamens than the normal ones; instead of five stamens the deformed flowers can have six to ten. Moreover, a number of other different deformations can arise in the stamens as well. For example the anomalous stamens can grow together (pl.' 5, g, j—l; pl. 6, n). Because of that two or even three anthers can arise on one widened filament (pl. 5, g, j, 1). The stamens can also grow together with the corolla (pl. 5, h, i, q). Besides that both strains can cause transformation of stamens into leaf-like organs (pl. 5, o, p). The cross sections of such stamens (pl. 5, r) can show only two instead of four cavities.
Along with the shortening of the other flower parts, the style of the pistil also becomes shorter (pl. 4, k; pl. 7, a — d). Strain B15 can cause a disappearing of the style entirely so that the stigma is placed directly on the ovary (pl. 5, c). Sometimes the style is less shortened than the corolla and thus the style sticks out from the tube of the corolla (pl. 12, c). The stigma and the ovary are usually somewhat bigger than those of the normal pistil.
The deformed pistils have often a greater number of tips on the stigma (pl. 7, e, h). The stigma is often strongly deformed under the influence of strain B15 and in many cases it has several minute tips covered with papillose hairs on their surface (pl. 5, c, e; pl. 7, d, f).
The normal ovaries or the fruit are composed of two carpels; they are two-celled at the top and four-celled at the basis. The number of carpels and ovary cells in the less deformed fruit can be the same as in the normal one (pl. 11, l — p, w, x). However, sometimes the deformed fruit has an increased number of carpels and ovary cells. For example on pl. 11, q — t are represented four sections of different heigts of a fruit. This fruit, infected with strain B12 is composed of three carpels. Similar relations exist also in the fruit on pl. 11, u, v. Anomalous ovaries can be composed even of five carpels (pl. 10, b). Sometimes the anomalies are so complicated that we cannot with certainy establish of how many carpels the ovary is made (pl. 9, a, b). Strain B15 causes a specially interesting anomaly where the carpels at the top of the ovary remain open (pl. 13); through that aiperture we can see the inside of the ovary. The aperture at the top of the ovary is often placed laterally as well (pl. 10, a). On account of that the placenta with ovules is exposed to outer conditions directly. The spines in particular places of the deformed fruit often lack completely or are strongly stunted (pl. 11, c, e — i).
On basis of the described symptoms we can see that strains B13 and B15 produce the most severe anomalies. Besides the shoe-string leaf they cause also peculiar alterations of the stigma (formation of an aperture at the top of the stigma, of a great number of stigma tips). On the contrary the green strans Bll and B12 are comparatively milder strains; they produce neither the shoe-string leaf nor the opening of the pistil. According to these considerable differences it is easy to differentiate strains B13 and B15 on the one hand from strains Bll and B12 on the other hand. The point to stress is that deformations of leaf, flower and fruit of Datura stramonium, can arise in both groups of CMV strains, the green and the yellow.
From these data we can see that the investigated strains on the leaf of Datura stramonium cause similar alterations to those which Lovi- solo and Benetti (1961) have described in Italy. Strains Bll, B12, B13 and B15, according to the alterations which they cause on the leaf, the flower and the fruit of this plant, agree considerably with a group of CMV strains which Kovacevski (1965) has described in Bulgaria. As strain B13 comes from England and strain Bll from Germany, we can conclude that the strains of CMV that cause deformations on Datura are spread all over Europe. On basis of the symptoms caused by strain B15, that comes from USA, we can consider that these strains of CMV exist in America as well.
Ključne riječi
Hrčak ID:
154818
URI
Datum izdavanja:
31.12.1968.
Posjeta: 1.177 *