ABSTRACT. Reciprocal cleft and pistillate floral bud grafts were made between parthenocarpic 'Fertilla' and nonparthenocarpic. 'MSU 713-5' cucumber ...
Plant Physiol. (1975) 55, 1107-1109
Parthenocarpic Fruit Development from Grafted Ovaries of Cucuminis sativus L. Received for publication November 8, 1974 and in revised form January 16, 1975
DANIEL J. CANTLIFFE1 AND SHARAD C. PHATAK Horticultural Experiment Station, Simcoe, Ontario, Canada ABSTRACT Reciprocal cleft and pistillate floral bud grafts were made between parthenocarpic 'Fertilla' and nonparthenocarpic 'MSU 713-5' cucumber (Cueumis sativus L.) lines to localize the site for stimulation of parthenocarpic fruit set. No fruit set on 'MSU 713-5' controls, scion grafted to 'Fertilla,' or rootstock with 'Fertilla' as the scion. 'Fertilla' controls, rootstock, and scions all produced parthenocarpic fruit when grafted to 'MSU 713-5.' When pistiliate floral buds of 'MSU 713-5' were grafted to 'Fertilla,' no fruit were produced. However, individual immature pistillate buds of 'FertilLa' developed into mature fruits when grafted onto 'MSU 713-5.' Hence, the immature ovary is the site of stimulation for parthenocarpic fruit set in cucumber.
Parthenocarpy in the cucumber can be induced genetically by the incomplete dominant gene (P) (8), or chemically by auxins (5, 7), gibbereilins (4, 5), and auxin transport inhibitors (2, 3, 9, 10). The action of the gene is not known. A correlation between high auxin content and seedlessness has been shown for cultivars of citrus and grape (6). Auxin transport inhibitors such as 2,3, 5-triiodobenzoic acid, methyl-2-chloro-9-hydroxyflurene-9-carboxylate (chlorflurenol), and 3,3a-dihydro-2-(P-methoxyphenyl)-8H-pyrazolo[5, 1-a]-isoindol-8-one have been shown to be the strongest inducers of parthenocarpy in cucumber. Ovaries treated with these auxin transport inhibitors contain a higher content of compounds with auxin-like activity than nontreated ovaries (1). Elassar et al. (5) induced parthenocarpy by treating individual cucumber flowers with IAA, p-chlorophenoxyacetic acid (4-CPA), /3-naphtoxyacetic acid (/B-NOA), GA3, GA4+,, and BA. However, only the synthetic auxins and BA induced parthenocarpy when applied to the whole plant. Cantliffe (unpublished data) effectively induced parthenocarpy in cucumbers with chlorflurenol or (NAA) when either the whole plant, including open flowers, was treated or when individual flowers were treated at anthesis. No fruit developed when only individual leaves or the growing tip were treated. This study was initiated to determine if a genetically parthenocarpic cucumber line could stimulate fruit development in a nonparthenocarpic line and to localize the tissues involved in parthenocarpic fruit set.
MATERIALS AND METHODS Parthenocarpic 'Fertilla' and nonparthenocarpic 'MSU 7135' cucumber (Cucumis sativus L.) seedlings were grown in 15cm pots in a 1:1:1 sand-soil-peat mix in the greenhouse. The temperature was maintained at 25 C during the day and 21 C at night and daylength was 14 hr. Insects were excluded from the greenhouse in order to prevent pollination. Cleft Grafts. Reciprocal cleft grafts were made between 6week-old seedlings of the parthenocarpic and nonparthenocarpic lines. Rootstocks had three true leaves below the graft. Each graft union was bound with a small piece of plastic drinking straw and a latex bandage. The grafted plants were placed in a shaded plastic tent with 100% relative humidity for 4 days. Subsequently, the humidity was slowly reduced over a 4day period, then the plants were transferred to ambient greenhouse conditions. Bud Grafts. Immature pistillate and pistillate flowers at anthesis were grafted reciprocally between the two cucumber lines. The grafts were handled in the same manner as the cleft grafts except that buds were grafted onto plants that were 10 weeks old or older. Flower buds were grafted onto leaf petioles and the main stem at the last expanded leaf. Bud grafts were more successful if a small piece of stem remained at the peduncle. The plants were placed in the plastic tent and removed as described before. Both grafting experiments were repeated at least four times. Eight plants of each cleft graft were made each time the experiment was repeated. At least 25 pistillate flowers of each bud graft were used each time the experiment was repeated.
RESULTS AND DISCUSSION Reciprocal cleft grafts between the parthenocarpic and nonparthenocarpic lines did not alter internode length of the scion or total growth. There were no general alterations of morphological characteristics of either line and no incompatibility of cleft or bud grafts (Fig. 1). Fruit did not develop on the nonparthenocarpic 'MSU 713-5' controls or on 'MSU 713-5' rootstocks and scions when grafted with 'Fertilla' (Table I). Nongrafted 'Fertilla' produced approximately four parthenocarpic fruit per plant. 'Fertilla' rootstock or scions produced 1 to 1.5 fruits per plant when no leaves from either line were removed or when the leaves from 'MSU 713-5' were removed. The number of fruit per plant was reduced to 0.4 when the leaves of 'Fertilla' were removed on either the stock or the scion. It seemed as though at least a partial stimulus for parthenocarpy may have come from the leaves of 'Fertilla.' However, the leaf area and hence the available metabolites for fruit development were reduced when 'Present address: Vegetable Crops Department, IFAS, Univer- leaves of 'Fertilla' were removed compared to removal of sity of Florida, 3026 McCarty Hall, Gainesville, Fla. 32611. 'MSU 713-5' leaves. This was attributable to the comparatively 1107
1108
CANTLIFFE AND PHATAK
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Plant Physiol. Vol. 55, 1975
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FIG. 2. Fruit of 'Fertilla' from flower buds grafted onto 'MSSU 713-5' at the stem tip and on a bottom leaf petiole. Arrow indicates site of graft.
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larger size of 'Fertilla' leaves. Also, leaves of 'Fertilla' had no apparent effect on inducing parthenocarpy in 'MSU 713-5.' In the next experiment, only flower buds were grafted, in order to remove the possible influence of leaves on parthenocarpic fruit set. None of the 'MSU 713-5' flowers produced fruit when grafted onto 'Fertilla' (data not shown). However, approximately 44% of the 'Fertilla' flowers produced fruit when grafted on 'MSU 713-5' (Fig. 2). None of the fruit that developed produced seed (Fig. 3). Immature flower buds gave a higher percentage of graft success than pistillate flowers grafted at anthesis. Thus, a higher percentage of fruit developed from these flowers. It seems that the stimulus for genetic parthenocarpy is localized in the immature ovary. This is in agreement with
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FIG. 3. Mature seedless fruit of 'Fertilla' which developed from an immature flower bud grafted onto 'MSU 713-5.' Arrow indicated site of graft.
Plant Physiol. Vol. 55, 1975
PARTHENOCARPIC FRUIT DEVELOPMENT
report on chemical stimulation of parthenocarpic fruit development, in that the apparent effect of the chemical was on the ovary and not some other tissue (1).
5. 6.
LITERATURE CITED 7.
JR. AND B. QUEBEDEAUX, JR. 1974. Parthenocarpy in cucumber: Mechanism of action of auxin transport inhibitiors. J. Amer. Soc. Hort. Sci. 99: 385-390. 2. CANTLIFFE, D. J. 1972. Parthenocarpy in the cucumber induced by some plant growth-regulating chemicals. Can. J. Plant Sci. 52: 781-785. 3. CANTLIFFE, D. J., R. W. ROBINSON, AND R. S. BASTDORFF. 1972. Parthenocarpy of cucumber induced by triiodobenzoic acid. Hortscience 7: 285-286. 4. CHOUDBURY, B. AND S. C. PHATAX. 1959. Sex expression and fruit development 1. BEYER, E.
M.,
8. 9. 10.
in cucumber (Cucumis sativus L.) as affected by gibberellin. Indian J. Hort. 16: 233-235. ELASSAR, G., J. RtTDICH, D. PALEVITCH, AND N. KEDAR. 1974. Induction of parthenocarpic fruit development in cucumbers by growth regulators. Hortscience 9: 23-239. GTTSTAFSON, F. G. 1939. The cause of natural parthenocarpy. Amer. J. Bot. 26: 135-138. HOMAN, D. N. 1964. Auxin transport in the physiology of fruit development. Plant Physiol. 39: 982-986. PIKE, L. M. AND C. E. PETERSON. 1969. Inheritance of parthenocarpy in the cucumber (Cucumis sativus L.). Euphytica 18: 101-105. QUEBEDEAUX, B. AND E. M. BEYER. 1972. Chemically induced parthenocarpy in the cucumber by a new inhibitor of auxin transport. Hortscience 7: 474-476. ROBINSON, R. WV., D. J. CANTLIFFE, AND S. SHANNON. 1971. Morphactininduced parthenocarpy in the cucumber. Science 171: 1251-1252.
