THE GENUS PYTHIUM In the West Bank and Gaza Strip by DR. MOHAMMED S. ALl - SHr A YEH Department of Biological Sciences An - Najah National University Published by Research and Documentation Centre An- ajah National University - Nablus 1986 ,I.' Copyright © 1986 by The Resarch and Documentation Centre, An': Najah National University, Nablus PREFACE This monograph is aimed at providing a well illustrated guide to the species of Pythium in the West Bank and Gaza Strip. A key for all the species recovered is given. However, the reader is advised to always check through the description given to the species to make sure that he has made the right identification. This description has been based on several freshly recovered isolates that came from different habitats in order to account for inter and intraspecific variations. A guide to the isolation methods is also provided. Also, information on the distribution and host range of the different species is given. I believe that we still have a lot to learn about this important group of fungi especially with respect to their physiology, genetics, and taxonomy. However, this book has covered fundamental topics on the genus Pythium and that it would be particularly useful to students of mycology, botany, plant pathology, ecology, and biology ACKNOWLEDGNENTS I would like to exprees my gratitude to a number of people who directly or indirectly helped in the preparation of this monograph. I am in the first place indebted to the Dea n of the Research and Documentation Centre for allowing the publication of this book. I also wish to express special thanks to my research students, laboratory technicians, and research assistants at the Department of Biological Sciences, and friends who have offered help and encouragement when I most needed it. Lastly but no means least I acknowledge the financial support donated generously by the Department of Biological Sciences throughout this work. CONTENTS Summary 1 J. Introduction 2-4 II. Materials and Methods 5-9 III. Key to Pythium spp isolated in the West Bank and Gaza Strip. 10 - 15 I V. Desceiptions of species 16 - 66 V. Host list 67 - 68 V I. References 69 -74 VII. Index of fungal names. 75 - 76 VIII. Arabic abstract. 78 SUMMARY A key to the 48 taxa of Pythium recorded so far from the West Bank and Gaza Strip is given.isolation and preservation methods are also provided. The following species are described and illustrated: P. acanthicum Drechsler, P. anandrum Drechsler, P. aphanidermatum (Edson) Fitzp, P. coloratum Vaartaja, P. conidiophorum loki, P. debaryanum auct non Hesse, P. dissimile Vaartaja, P. dissotocum Drechsler, P. echinulatum Matthews, P. graminicola Subramaniam, P. intermedium de Bary, P. irregulare Buisman, P. iwayamqi S. Ita, P. mamillatum Meurs, P. middletonii Sparrow, P. monospermum Pringsh, P. nagaii S. Ita & Tokunga, P. oligandrum Drechsler, P. papillatum Matthews, P. paroecandrum Drechsler, P. pulchrum Minden, P. rostratum Butler, P. salpingophorum Drechsler, P. spinosum Sawada, P. splendens Braum, P. sylvaticum Campbell & Hendrix, P. torulosurn Coker & Patterson, P. ultimum var sporangiiferum Drechsler, P. ultimum Trow var ultimum, P. vantrepoolii V. Kouyeas, and P. vexans de Bary. Descriptions were produced from the study of several isolates in order to account for intraspecific variation. The other 17 taxa were outlined briefly. These taxa were isolated only once or twice and/ or failed to from sexual reproductive structures following their identification (P. deliense Meurs, P. dimorphum Hendrix & Campbell, P. hypogynum Middelton, P. myriotylum Drechsler, P. orthogonon Ahrens, P. periplocum Drechsler, P. pyrilobum Vaartaja, and P. tracheiphilum Matta), taxa without oogonia (P. group 'F', P. group 'G', P. group 'HS', and P. group 'L'), and taxa described by the author in 1982 from Britain (P. lucens, P. lutarium, p. minor, p. pachycaule, and P. parvum) and were also isolated from the West Bank. Occurence of the different taxa in the West Bank and Gaza Strip as well as in other neighbouring countries is briefly outlined. All known records of rare species are mentioned. All known host records of Pythium from the West Bank and Gaza Strip are also listed. I. INTRODUCTION The genus Pythium is now regarded as the type genus of the family Pythiaceae Schroter in the order Peronosporales of the class Ooomycetes (Waterhouse, 1973; Plaats-Niterink, 1981). The genus was introduced by Pringsheim (1858). His genus was based on two fungi, Pythium monospermum and P. entophytum. The latter fungus was transferred to Lagenidium (Zopf, 1890), so that P. monospermum remained as the type species. Pringsheim (1858) placed Pythium in the Saprolegniaceae, but de Bary (1881) placed the genus in the Peronosporaceae. Schroter (1897) created the family Pythiaceae for the genera Pythium and Nematosporangium. Butler (1907) did not accept Nematosporangium as representing a distinct group of species, so he included all the species under Pythium. Monographs on the genus have been published by Butler (1907), Matthews (1931), Sideris (1931, 1932), Middelton (1943), and Frezzi (1956). Waterhouse (1967, 1968) compiled the original descriptions and illustrations of all Pythium taxa described at that time; a total of )79 taxa. She produced a key for eighty nine taxa which she considered as .valid and rejected ninety taxa. This key depended heavilly on the original descriptions of the species. Since many of these were produced from the study of single isolates, without taking into consideration the possible sources or ranges of variation, original descriptions were often inadequate for comparative purposes. As a result the key frequently has to depend upon small differences in reproductive cell-size; it also emphasizes some nonmorphological characters. Robertson (1980) produced a key to the twenty seven species of Pythium recorded so far from New Zealand; illustrations and descriptions were given for sixteen species. Plaats-Niterink (1981) published the latest monograph of the genus Pythium. She recognised and described eighty five species, seven of which are heterothallic. Descriptions were again based on single isolates. Therefore, extent of intraspecific variation was not accounted for in both Robertson and Plaats-Niterink keys. However, it is difficult to assess intraspecific variation from published descriptions since the majority of these were prepared from single isolates. Pythium species occupy a wide diversity of habitats. They can be found as saprobes in fresh and salt water and in soil, and as parasites in aquatic and terrestrial plant material, fresh water and marine algae, fungi, invertebrates and vertebrates (Middleton, 1943; Plaats-Niterink, 1981). Species of Pythium have been often referred to as 'sugar fungi' (Garret, 1951; Burges, 1958), a term which infers their inability to degrade complex carbohydrate polymers, like cellulose. However, it has been recently found that several species of Pythium are capable of degrading cellulose (Taylor & Marsh, 1963; Tribe, 1966; Willoughby & Redhead, 1973; Park, 1980 a,b; Deacon, 1979). It has been therefore suggested (Deacon, 1979) that the cellulolytic activity of Pythium species removes these fungi from the substrate group 'sugar fungi'. 2 Pythium species such as P. periplocum, and P. acanthicum have been reported as mycoparasites on both other species of Pythium such as P. ultimum, P. debaryanum, P. irregulare and P. salpingophorum (Haskins, 1963; Deacon, 1976; Vesely, 1978; Deacon & Henry, 1978) and other fungi such as Fusarium roseum (Deacon & Hery, 1978). Pythium oligandrum was found by Deacon (1976) to be an efficient mycoparasite of Rhizoctonia solani, Fusarium culmorum and a Trichoderma species and the possibility of using this fungus in bilogical control of damping-off diseases has been considered (Deacon, 1976; Vesely, 1978). Pythium species have also been reported from nests, intestines, feathers of free living birds in Czechoslovakia and Yugoslavia (Hubalek, 1974 a,b), and droppings of birds previousely fed with these fungi (Thornton, 197 I). Pythium species have also been recorded from fish (Scott & O'Bien, 1962), Daphnia and Bosmina (Peterson, 19lOj Plaats-Niterink, 1972, 1975), and crustacean eggs and mosquito larvae (Stanghellini, 1974). The extent of pathogenicity to animals is not known. Austwick & Copland (1974) found that Hyphomyces destruens-equi which might be a Pythium species, is probably pathogenic to horses. Pythium spp are distributed worldwide (Tompkins, 1975; Domsch et ai., 1980; Plaats- Niterink, 1981). Some species such as P. ultimum, P. rostratum, and P. irregulare have appeared consistently in the lists derived from the majority of the reports in the literature (Vaartaja, 1968; Hendrix & Campbell, 1970; Plaats- Niterink, 1975; Robertson, 1980; Ali, 1982, 1985). On the other hand other species such as Pythium deliense, P. aphanidermatum and P. myriotylum have a high temperature optimum and are apparently restricted in distribution and economic range to warm climates (Garren, 1970; McCarter & Littrell, 1970; Ali, 1985).Of the.eighty five species recognized by Plaats-Niterink (1981) more than sixty species are either known only from original description or have been recorded so seldom that comments on their distribution are impossible. Many Pythium species are soil inhabitants, living saprophytically or parasitically (Stanghellini, 1974; Domsch et al., 1980; Ali, 1982) Some Pythium species are among the most destructive plant pathogens (Agrios, 1978). Their pathogenic capacity