1 Distribution and economic importance K.Evansandf.A.Rowe 1.1 INTRODUCTION The family Heteroderidae of plant parasitic nematodes contains the cyst­ forming species within the sub-family Heteroderinae, within which the numbers of genera (not all cyst-forming) and species described have increased greatly over the last five decades. When Franklin (1951) pub­ lished her book on "The cyst-forming species of Heterodera", cyst nema­ todes were already a major concern and were known to cause serious yield lasses in important food crops such as potatoes, cereals, brassicas, tomatoes and sugar beet. The genus Heterodera Schmidt 1871 was, at that time, considered tobe largely temperate, with about 12 species. Today, 67 valid species are recognized in the genus Heterodera alone (Table 1.1). After many studies and revisions in classification (Mulvey, 1972; Stone, 1977; Luc, Maggenti and Fortuner, 1988; Baldwin and Schauest, 1990), the specific characters of many other species that were once members of the genus Heterodera have been accommodated in new genera. These new genera of cyst-forming species are Globodera, Punctodera, Cactodera, Afe­ nestrata and Dolichodera, which are listed with the species they contain in Table 1.2. The cyst-forming genera of the Heteroderinae seem, in general, to have hosts within particular plant families. For instance, the Poaceae support many species of Heterodera and Punctodera. On the other hand, there are examples of unusual host specificity within genera, such as Cactodera betulae, found normally on birch and occasionally alder whilst other species of Cactodera are found on members of the Cactaceae, Amar­ anthaceae and Chenopodiaceae. The Cyst Nematodes. Edited by S.B. Sharrna. Published in 1998 by Chaprnan & Hall, London. ISBN 0 412 75530 0. 2 Distribution and economic importance Table 1.1 Cyst-forming species of the genus Heterodera Schmidt, 1871 Species Main host plant family Species Main host plant family amygdali Rosaceae limonii Plumbaginaceae arenaria Poaceae litoralis Chenopodiaceae aucklandica Poaceae longicolla Poaceae avenae Poaceae mani Poaceae bergeniae Saxifragaceae medicaginis Fabaceae bifenestra Poaceae mediterranea Anarcardiaceae cajani Fabaceae menthae Lamiaceae canadensis Cyperaceae methwoldensis not known cardiolata Poaceae mothi Cyperaceae carotae Umbelliferae oryzae Poaceae ciceri Fabaceae oryzicola Poaceae cruciferae Cruciferae oxiana Chenopodiaceae cynodontis Poaceae pakistanensis Poaceae cyperi Cyperaceae phragmitidis Poaceae daverti Fabaceae plantaginis Plantaginaceae delvii Poaceae polygoni Polygonaceae elachista Poaceae raskii Cyperaceae fici Moraceae rosii Polygonaceae filipjevi Poaceae sacchari Poaceae galeopsidis Lamiaceae salixophila Salicaceae gambiensis Poaceae schachtii* Chenopodiaceae glycines Fabaceae sinensis Poaceae glycyrrhizae Fabaceae sonchophila Asteraceae goettingiana Fabaceae sorghi Poaceae graduni Polygonaceae spinicaudata Poaceae graminis Poaceae tadshikistanica Asteraceae graminophila Poaceae trifolii Fabaceae hordecalis Poaceae turangae Salicaceae humuli Moraceae turcomanica Chenopodiaceae iri Poaceae urticae Urticaceae kirjanovae Betulaceae ustinovi Poaceae latipons Poaceae uzbekistanica Salicaceae lespedezae Fabaceae zeae Poaceae leuceilyma Poaceae * Type species Note: Many species of Heterodera will parasitise plants of more than one family, notably the type species H. schachtii. The main host plant family given is generally the most important host family but, occasionally, the family with which the species was first associated. 1.2 DISTRIBUTION It is now known that, far from being exclusively temperate, many cyst nematodes (and also non-cyst-forming species of the Heteroderinae) are present in tropical and sub-tropical regions. The numbers of known Distribution 3 Table 1.2 Cyst-forming species of genera other than Heterodera Genus Authority Species Hast plant family Afenestrata (5) Baldwin and Bell, 1985 africana* Poaceae axonopi Poaceae koreana Poaceae orientalis not known sacchari Poaceae Cactodera (11) Krall and Krall, 1978 acnidae Amaranthaceae amaranthi Amaranthaceae aquatica not known betulae Betulaceae cacti* Cactaceae chaubattia Rosaceae estonica Polygonaceae eremica Chenopodiaceae milleri Chenopodiaceae thornei Portulaceae weissi Polygonaceae Dolichodera (1) Mulvey and Ebsary, fluvialis* Poaceae 1980 (unconfirmed) Globodera (12) Skarbilovich, 1959 achilleae Asteraceae artemisiae Asteraceae hypolysi Asteraceae leptonepia unknown, possibly Solanaceae millefolii Asteraceae (sp. inq.) mirabilis unknown (sp. inq.) pallida Solanaceae rostochiensis* Solanaceae tabacum Solanaceae solanacearum tabacum Solanaceae tabacum tabacum Solanaceae virginiae zelandica Onagraceae chalcoensis Poaceae Punctodera (3) Mulvey and Stone, matadorensis Poaceae 1976 punctata* Poaceae * Type species 4 Distribution and economic importance species increase as awareness of the darnage they cause is observed and taken into account by farmers, agricultural advisers and, eventually, nematologists. The genus Afenestrata was first described by Baldwin and Bell (1985) after close re-examination of Sarisodera africana; the num­ ber of species has now risen to five. The genus Globodera is thought to have originated in the Andean regions of South America (Krall and Krall, 1978), and divides geographically into two main groups, the G. tabacum group of species from North America and the potato cyst nematodes (G. pallida and G. rostochiensis) from South America. Although Globodera is considered to have evolved in the Americas, mainly on members of the Solanaceae, there is a small group of Globodera species from the Old World which parasitize members of the Asteraceae, and G. zealandica is a species indigenous to New Zealand whose hosts are woody trees from the Onagraceae (Wouts, 1984). The species parasitizing the Asteraceae may represent a group that have co-evolved with their hosts in an isolated evolutionary niche after the splitting of Gondwanaland (Stone, 1983), and they are distributed in Europe, the former USSR, China and Japan. It is of note that they may be able to survive in extreme climatic conditions. The most economically important species of the cyst-forming nematodes are within the genera Heterodera and Globodera. The non­ cyst-forming genera of the Heteroderinae are listed in Table 1.3. The most important cyst-forming genera, Heterodera, Globodera and Punctodera, Table 1.3 Non-cyst forming genera within the sub-family Heteroderinae Number of Genus Authority species Atalodera Wouts and Sher, 1971 4 Bellodern Wouts, 1985 1 Bilobodera Sharma and Siddiqi, 1992 2 Brevicephalodera Kaushal and Swarup, 1989 1 Camelodera Krall, Shagalina and Ivanova, 1988 1 Cryphodera Colbran, 1966 5 Ekphymatodera Baldwin, Bernard and Mundo-Ocampo, 1 1989 Hylonema Luc, Taylor and Cadet, 1978 1 Meloidodera Chitwood, Hannon and Esser, 1956 9 Rhizonema Cid del Prado Vera, Lownsbery and 1 Maggenti, 1983 Sarisodera Wouts and Sher, 1971 1 Thecavermiculatus Robbins, 1978 4 Verutus Esser, 1981 2 + 1 undescribed Heterodera 5 important cyst-forming genera, Heterodera, Globodera and Punotcdera are considered separately below and the non-cyst-forming genera within the Heteroderinae are considered briefly as a group. 1.2.1 Heterodera Members of the genus Heterodera are believed originally to have para­ sitized ancient orders of tropical plants and to have evolved to the present time on those members of the plant families that may stillexist (Krall and Krall, 1978). For convenience, the members of the genus Heterodera are considered here under the headings Tropical, Sub-tropical and Temperate, but it must be recognized that there is considerable overlap between these empirical groupings. (a) Tropical In the tropics, at least 23 species of cyst nematode have been found (Table 1.4), plus other non-cyst-forming genera of the Heteroderidae such as Bilobodera (Sharma and Siddiqi, 1992), Brevicephalodera (Kaushal and Swarup, 1989) and Hylonema (Luc, Taylor and Cadet, 1978). As far as is known, the cyst-forming species are more damaging than non-cyst-form­ ing species and, according to Luc (1986), the most economically-import­ ant in the tropics are H. oryzae, H. sacchari, H. oryzicola, H. cajani and H. zeae, to which we add H. sorghi. Heterodera oryzae and H. oryzicola both attack the staple crops rice and bananas. The type locality for H. oryzae is the Ivory Coast on rice and it is found in Senegal, parasitising banana. It has been recorded by Shahina and Maqbool (1995) from Pakistan and by Chinnasri, Tangchitsamkid and Toida (1994) from Thailand. Heterodera oryzicola is present in Goa, Haryana and Kerala in India on upland rice, and on banana (Musa acuminata x M. balbisiana) and Cynodon dactylon (Charles and Venkitesan, 1978; Rao and Jayaprakash, 1978). Heterodera sacchari is morphologically very similar to H. oryzae with some overlap in morphometric values. Although H. sacchari was origin­ ally reported from sugar cane in the Congo, it has also been reported on sugar cane from other countries such as Nigeria (Jerath, 1968; Odihirin, 1975) and Pakistan (Maqbool, 1981), and from Saccharum spontaneum in India (Swarup, Prasad and Raski, 1964). It has also been reported as a parasite of rice (Merny, 1970; Babatola, 1983) and its distribution may even extend to Jamaica where it was reported in soil around sugar cane roots, although only second stagejuveniles were found (Singh, 1974). The other cyst nematode known to cause darnage to rice, H. elachista, has so far only been recorded from upland rice in Japan (Ohshima,