CROP SCIENCE, VOL. 49, SEPTEMBER– OCTOBER 2009 1667 RESEARCH J ATROPHA, commonly known as physic nut and belonging to the family Euphorbiaceae, is a multipurpose plant with great eco- nomic value. The genus encompasses 200 species of trees, shrubs, rhizomatous subshrubs, and herbs distributed mainly in dry tropi- cal regions of Mexico, Central America, and Africa (Dehgan and Webster 1979). It is believed to have been introduced in India by the Portuguese settlers during the 16th century. This plant is valued not only for its medicinal properties but also for resistant to various stresses, including drought tolerance (Takeda, 1982; Martin and Mayeux, 1985), minimal attacks by insect pests, and resistant to fusarial wilts (Sujatha and Prabakaran, 1997). The seeds of J. curcas contain 25 to 35% semidrying oil called curcas oil. Methylated Jatropha oil can efectively be substituted as diesel fuel. The oil is rich in hydrocarbon (27.0–48.5% seed oil content), and the fatty acid proile of J. curcas shows that oleic acid as the predominant fatty acid, while other species of Jatropha con- tain linoleic acid as the dominant fatty acid. In recent years, the genus has attracted several researchers for its seed oil as an alterna- tive source of fuel (Takeda, 1982; Banerji et al., 1985; Martin and Mayeux, 1985; Openshaw, 2000). Studies are being performed at the Forest College and Research Institute at Tamil Nadu Agricultural University, Mettupalayam, Tamil Nadu, India, to evaluate a wide range of seed and clonal sources of J. curcus (Paramathma et al., 2005). In addition, a Jatro- pha clonal gene bank has been established with 11 species (Senthil Investigation on Cross-Compatibility Barriers in the Biofuel Crop Jatropha curcas L. with Wild Jatropha Species R. Senthil Kumar,* K. T. Parthiban, P. Hemalatha, T. Kalaiselvi, and M. Govinda Rao ABSTRACT Interspeciic hybridization in Jatropha species plays a signiicant role in crop improvement by transferring useful traits such as yield, high oil content, maximum number of seeds, more femaleness, and hard stems for promoting Jatropha as a biofuel crop. The wide crosses among the species resulted in limited success due to pollen incompatability. Hence, the objec- tive of the study was to assess pre- and postzy- gotic barriers through pollen–pistil interaction between cultivated Jatropha curcas and other three wild Jatropha species. In this study, the cross J. curcas × J. gossypifolia, even though the pollen tubes reached ovaries after pollina- tion, failed to produce seeds, and the cross between J. curcas × J. podagrica indicated incompatibility signs of bulged pollen tubes coupled with reverse direction of pollen tube growth. The interspeciic cross of J. curcas with J. villosa showed crossability barriers of crinkled and twisted growth pattern of pollen tubes and failed to reach ovary. In the case of seling (J. curcas × J. curcas), pollen tubes reached ovary within an hour and produced normal seeds. Reciprocal crosses of these species exhibited successful fertilization of pollen tubes, but seed set was very low or no seed set was noticed. Forest College and Research Institute, Tamil Nadu Agricultural Univ., Mettupalayam, Tamil Nadu, 641 301, India. Received 16 Oct. 2008. *Corresponding author (senthilfcri@yahoo.co.in). Abbreviations: AP, after pollination. Published in Crop Sci. 49:1667–1674 (2009). doi: 10.2135/cropsci2008.10.0601 © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.