DIVERSITY AND DISTRIBUTION INTRODUCTION • The genus Dioscorea is one of the largest groups among OF THE GENUS DIOSCOREA IN monocotyledons belonging to the family Dioscoreaceae. • The members are commonly known as yams and are widely WESTERN GHATS cultivated for its edible tubers throughout tropics and occupies 3rd most important food crops in the world, next to cereals and pulses. • The word yams comes from Portuguese or Spanish name as “Inhame” which means “to eat”. Elsamma Joseph (Arackal) • The genus is distributed mainly in three centers of diversity A.G. Pandurangan & S. Ganeshan namely South Africa, South East Asia and Latin America. • The genus Dioscorea represents 850 spp. (Mabberley, 1997) and in India reported the occurrence of 32 spp. (Prain and Burkill, 1936, 1939) of which 17 are distributed in W. Ghats. • The genus shows close affinity towards dicotyledons by the presence of petiolate compound leaves, non sheathing leaf base, reticulate venation etc. Tropical Botanic Garden and Research Institute Palode, Thiruvananthapuram, Kerala REASONS FOR UNDERTAKING THE REASONS FOR UNDERTAKING THE STUDY STUDY…….contd • The taxonomy of quite a few species in this genus is considered • Many of the Dioscorea species serve as a “life saving” plant to be very problematic ( Prain and Burkill, 1936, 1939; Velayudan, group to marginal farmers and forest dwelling communities 1998) due to their continuous variability of morphological during the period of food scarcity (Arora and Anjula pandey, characters especially in aerial parts such as leaves and bulbils. 1996) This makes it difficult for taxonomists to segregate distinctly the various taxa of the genus. • Most of the tubers are edible and few are also used as medicinal. More than five million people are directly or • The dioecious nature, variable phyllotaxy, different phenology of indirectly depending on this crop for their food, feed, medicine the same species, deep seated bulky underground tubers etc etc. makes the group much more difficult for researchers and hence neglected. • Inspite of its manifold economic importance, the group is not taxonomically well studied for the last 60 years in India except • Against this background the present study has been undertaken to delimit and unravel the species complex that exists in the a few attempts by the regional flora researchers. Western Ghats based on fresh explorations from the wild as well as in cultivation. 1 GENERAL CHARACTERS OF THE CURRENT STATUS OF SPECIES OF GENUS DIOSCOREA DIOSCOREA - A GLANCE Most notable characters are : 1. World - 850 Species 2. South East Asia - 150 ” 1. Universal dioecism of the genus 3. India - 32 ” 2. Twining climbers without tendrils 3. Twining of the stem is species specific and producing leaves 4. Western Ghats - 17 ” and inflorescence 5. Present Study - 20 Species 5. Inflorescence are axillary spikes + 10 Varieties 6. Under ground part of all the species are tuberous + 8 unidentified species METHODOLOGY…….contd METHODOLOGY • Consulted the following herbaria for confirming the identity and authentication of specimens • A reconnaissance survey based on literature was done to determine the area of distribution in Western Ghats 1. Central National Herbarium (CNH), Calcutta. 2. Herbarium of Indian Museum, Calcutta. • Plant Specimens were collected from different areas of Western Ghats, 3. Herbarium of BSI, Pune. examined in the field itself and preserved in FAA for further studies 4. Blatter Herbarium, Bombay. • Field characters were noted then and there 5. Herbarium of BSI southern Circle (MH), Coimbatore, Tamil Nadu. 6. Herbarium of Madras Christian college, Tamil Nadu. • Ethno Botanical importance of each species were noted 7. Herbarium of Presidency College Madras, Tamil Nadu. 8. Herbarium of TBGRI Palode (TBGT), Trivandrum, Kerala. • Live photographs of the specimens were taken including tubers for identification 9. Herbarium of KFRI, Trichur, Kerala. 10. Herbarium of NBPGR, Trichur, Kerala. • Specimens were processed for Herbarium as per the standard procedures 11. Herbarium of University of Calicut (CALI), Kerala. • Established ex-situ gene bank at TBGRI for monitoring and • Illustrations were made based on fresh specimens evaluation. 2 RESULTS DIFFERENT SPECIES OF DIOSCOREA: A VIEW • During the course of present study, a total of 38 taxa have been collected and out of which 20 species and 10 varieties have been identified. • The remaining 8 taxa are imperfectly known owing to the lack of either male or female flowers. Therefore efforts are being continued to collect the materials to confirm the identity of these taxa, which may finally end up to new reports to Stem twining to the right. India or to Western Ghats Rachis of male inflorescence STATUS OF STATUS OF SPECIES SPECIES DISTRIBUTION DISTRIBUTION zigzag. 1. Dioscorea alata Cultivated 11.Dioscorea Jacqumontii nw, cw, sw (E & R) ABStem winged, terete. 2. Dioscorea anguina nw, cw, sw (E & R) 12. Dioscorea kalkaprasadii sw (E & R) Petiolar base with auricular 3. Dioscorea belophylla nw, cw, sw (E & R) 13. Dioscorea oppositifolia nw, cw, sw extension. 4. Dioscorea bulbifera nw, cw, sw 14. Dioscorea pentaphylla nw, cw, sw 5. Dioscorea composita Int. & Cult. 15. Dioscorea rotundata Int. & Cult. Tubers polymorphic. 6. Dioscorea esculenta Cultivated 16. Dioscorea spicata sw (E & R) 7. Dioscorea glabra nw, cw, sw 17. Dioscorea tomentosa nw, cw, sw C 8. Dioscorea floribunda Int. & Cult. 18. Dioscorea vexans Int. & Cult. Dioscorea alata L.: A. Habit- A portion of the male plant with 9. Dioscorea hamiltonii nw, cw, sw (E & R) 19. Dioscorea wallichii nw, cw, sw inflorescence, B. Bulbils, C. A portion of the female plant with 10. Dioscorea hispida nw, cw, sw 20. Dioscorea wightii sw (Endangered) inflorescence. Tubers of different varieties of Dioscorea alata L. A B DioscoreaDioscorea belophylla belophyllaVoigt.:Voigt.: A. A. Habit Habit with with female female inflorescence inflorescence B.B. Tubers Tubers 3 ••StemStem twiningtwining toto thethe leftleft andand narrowlynarrowly alatealate.. ••LeavesLeaves simple.simple. ••TubersTubers solitary,solitary, notnot A B A B stalked.stalked. ••BulbilsBulbils present.present. ••LeavesLeaves glabrousglabrous beneath.beneath. C C DioscoreaDioscorea bulbifera bulbiferaL.:L.: A. A. Infructescence, Infructescence, B. B. Tuber, Tuber, C. C. A A portion portion of of the the male male plantplant with with inflorescence inflorescence Dioscorea composita Hemsl.: A, B & C. Closer view of stands •• StemStem twiningtwining toto thethe leftleft andand terete.terete. •• LeavesLeaves simple,simple, pubescentpubescent beneath.beneath. B •• TubersTubers several,several, distinctlydistinctly stalked.stalked. •• TubersTubers longerlonger thanthan var.var. A esculenta.esculenta. •• BulbilsBulbils absent.absent. •• LeavesLeaves areare alsoalso largerlarger thanthan var.var. esculentaesculenta withwith A sharpsharp spines.spines. •• TubersTubers several,several, distinctlydistinctly stalkedstalked with with aa smallsmall matmat B ofof prickles.prickles. Dioscorea esculenta (Lour.) Burkill : A. Habit, B Tubers Dioscorea esculenta (Lour.) Burkill : A. Habit, B Tubers DioscoreaDioscorea esculenta esculenta(Lour.)(Lour.) Burkill Burkill var. var. fasciculata fasciculata:: A. A. Habit, Habit, B B Tubers Tubers 4 B • Tubers larger distinctly A stalked covered with a fine large mat of spines. • Leaves smaller. B C A Dioscorea floribunda Martens & Galeotti : A. Habit with female Dioscorea esculenta (Lour.) Burkill var. spinosa : A. Habit, B Tubers inflorescence, B & C Closer view of female inflorescence •• StemStem twiningtwining toto thethe right,right, wingedwinged withwith 88 B ridges.ridges. A •• RachisRachis ofof malemale inflorescenceinflorescence zig-zagzig-zag A B C DioscoreaDioscorea hamiltonii hamiltoniiHook.f.:Hook.f.: A. A. Habit, Habit, B. B. A A portion portion of of the the femalefemale inflorescence, inflorescence, C.Tubers C.Tubers C Dioscorea hispida Dennst. : – A & B. Habit, C. Tubers 5 •• StemStem twiningtwining toto thethe ** Stem Stem twiningtwining toto thethe left.left. right. right. ** Leaves Leaves compound,compound, A • Leaves opposite and AA • Leaves opposite and glabrousglabrous oror rustyrusty sub-opposite. sub-opposite. tomentosetomentose below.below. •• SecondarySecondary veinsveins ** Bulbils Bulbils present.present. obscureobscure onon bothboth sides.sides. B C BB DioscoreaDioscorea pentaphylla pentaphyllaL.L. : : A. A. Male Male plant plant with with inflorescence, inflorescence, Dioscorea oppositifolia L. : A. Habit with male inflorescence, B. Tuber Dioscorea oppositifolia L. : A. Habit with male inflorescence, B. Tuber B.B. Female Female plant plant with with inflorescence, inflorescence, C. C. Tuber Tuber ••LeavesLeaves glabrous,glabrous, A B opposite.opposite. A B ••StemStem withwith prickles,prickles, ••StemStem twiningtwining toto thethe twiningtwining toto right.right. left.left. •• Leaves Leaves compoundcompound andand tomentose.tomentose. •• Bulbils Bulbils absent.absent. C •• Tubers Tubers numerous.numerous. C D DioscoreaDioscorea tomentosa tomentosaKoenigKoenig ex ex Spreng. Spreng. : : A. A. Habit Habit with with male male inflorescence, inflorescence, DioscoreaDioscorea rotundata rotundataPoir.Poir. : : A. A. Habit, Habit, B B - - D. D. Tubers Tubers . B.B. Female Female infructescence, infructescence, C. C. Tubers Tubers 6 INTERESTINGINTERESTING COLLECTIONSCOLLECTIONS OFOF DIOSCOREADIOSCOREA ••StemStem twiningtwining toto thethe rightright andand withoutwithout wings.wings. A ••RachisRachis