Available online at www.ijpab.com Rathore Int. J. Pure App. Biosci. 6 (5): 346-354 (2018) ISSN: 2320 – 7051 DOI: http://dx.doi.org/10.18782/2320-7051.6878 ISSN: 2320 – 7051 Int. J. Pure App. Biosci. 6 (5): 346-354 (2018) Research Article Host Choice in Rotylenchulus Species Y. S. Rathore* Principal Scientist (Retd.), Indian Institute of Pulses Research, Kanpur-208 024 (U.P.) India *Corresponding Author E-mail: [email protected] Received: 12.09.2018 | Revised: 9.10.2018 | Accepted: 16.10.2018 ABSTRACT The reniformis nematodes of the genus Rotylenchulus (Haplolaimidae: Nematoda) are sedentary semi-endoparasites of numerous crops. There are ten species out of which R. reniformis and R. parvus are important, and three species (R. amanictus, R. clavicadatus, R. leptus) are monophagous: two on monocots and one on Rosids. In general, Rotylenchulus species are capable of feeding from very primitive Magnoliids to plants of advanced category. Preference was distinctly observed towards the plants in Rosids (42.779%) followed by monocots (23.949%) and Asterids (21.755%). The SAI values were also higher for these groups of plants. The study on lineages further revealed intimate affinity to febids (25.594%), followed by commelinids (18.647%), malvids (16.088%), lamiids (11.883%), and campanulids (9.141%). Poales contribution within commelinids was 65.353%. Maximum affinity of Rotylenchulus species was observed by their association with plants from families Poaceae (7), followed by Fabaceae (6), Malvaceae (6), Asteraceae (4), Oleaceae (4), Soanaceae (4) and so on. Key words: Agiosperms, Gymnosperms, APG IV system, Reniform nemtodes, Monocots, Rosids, Asterids INTRODUCTION number of crops, whereas the other eight Plant parasitic nematodes pose a great species are of limited importance. It has been constraint on food and fruit production observed that nematodes, in general, parasitize throughout the world. Damage caused by plant hosts from selected group of plants as nematodes has been estimated at US $ 80 observed by Rathore and Ali13 in Meloidogyne billion per year 11. The reniform nematodes of incognita, Rathore and Tiwari14 in root-knot the genus Rotylenchulus (Haplolaimidae : nematodes, Rathore and Tiwari15 in Nematoda) are sedentary semi- endo-parasites Aphelenchoides species, and Rathore12 of numerous herbaceous and woody plants17. Xiphinema americanum. It was, therefore, They are predominantly distributed in tropical obvious to study the host preference of and subtropical climates. Out of ten species of Rotylenchulus species in relation to various Rotylenchulus, R. reniformis and R. parvus are host plants and particularly to their affinity to important and pose significant threat to large taxonomic group(s) of plants. Cite this article: Rathore, Y.S., Host Choice in Rotylenchulus Species, Int. J. Pure App. Biosci. 6(5): 346- 354 (2018). doi: http://dx.doi.org/10.18782/2320-7051.6878 Copyright © Sept.-Oct., 2018; IJPAB 346 Rathore Int. J. Pure App. Biosci. 6 (5): 346-354 (2018) ISSN: 2320 – 7051 MATERIAL AND METHODS respectively and supported the preference Host plants of different species of based on percent host plants in each taxonomic Rotylenchulus reported by Nemaplex10 and group. Contribution of Superasterids (4.570%) Marias and Swart9 were downloaded and and COM clade (4.388%) in host range is arranged according to the APG IV1 system of worth mentioning and both of them got high classification of angiosperms which is based SAI values because more host plants got on molecular and morphological studies of grouped comparatively in less number of plants. The families and orders thus reported in families and orders. Gymnosperms were also the literature were changed to as mentioned by accepted as preferred hosts by some the Wikipedia18 for different plants. This Rotylenchulus species (Table 1). resulted in placing of certain plants to new When the preference to taxonomic families and also placing existing families to groups was evaluated on the basis of ratios of new families/orders. Readers, therefore, may host species to their genera, families and not find the same names of families and orders orders, the highest ratios were observed in as reported earlier in the literature. APG IV monocots, Rosids and Asterids indicating system is delineated to several clades. But closeness of food plants with their genera, broadly speaking, angiosperms divided into families and orders.. The same was also monocots and eudicots (dicotyledons) clades visualized in case of Superasterids and COM and Eudicots into basal and core Eudicots. The clade plants where host species utilized less classification is still in the developing stage number of families and orders and ultimately and many families yet to find suitable place. showed greater intimacy although had less These uncertain families/ orders have been number of host plants (Table 1). tentatively placed in COM clade. The Association of host plants in three affiliation of host plants was decided on the major taxonomic clades was further evaluated basis of number of hosts parasitized as well as by placing number of plants to different by computing the Affiliation Indices following lineage groups (Table 2). Febid group the method of Rathore and Tiwari14. General contributed 25.594% host plants followed by Affiliation Index (GAI) was calculated for malvids (16.088%). In Asterids, 11.883 and different Rotylenchulus species and Specific 9.141% plants were parasitized in lamiids and Affiliation Index (SAI) for taxonomic groups campanulids, respectively. However, in of plant species. Some ratios viz., monocots, the commelinids showed maximum species:genus, species:family and affinity having 18.647% plants and within species:order were also calculated to support commelinids , the Poales contribution was to the host affinity. The terms mono-, oligo-, and the tune of 65.353%. In spite of large number polypagous were adopted as defined by of plants in the host range, Rotylenchulus Berneys and Chapman3. species preferred plants of certain taxonomic groups. RESULTS AND DISCUSSION Information on host range of Results are reported in Table 1 through 4. individual species of Rotylenchulus is givan in Perusal of Table 1 revealed that Rotylenchulus Table 3. Out of ten Rotylenchulus species, R. species, in general, are capable of parasitizing anamictus, R. clavicaudatus and R. leptus on all kinds of plants from very primitive showed monophagy and two were Magnoliids to plants of developed category. monophagous on monocotyledons and one on However, preference was distinctly observed Rosids. Among the polyphagous species only towards the plants of certain groups like R. macrodoratus and R. parvus had moderate monocots, Rosids and Asterids. Rosids number of host plants. The biggest host range contributed 42.779% plants followed by was of R. reniformis which reported to invade monocots (23.949%) and Asterids (21.755%). 460 plant species from all taxonomic groups. The SAI values were also higher for these The GAI values of all the monophagous groups of plants viz., 1.242, 1.064, and 0.823 species was 1.000, whereas in polyphagous for Rosids, monocots and Asterids, species it ranged from 0.500 to 0.737 except in Copyright © Sept.-Oct., 2018; IJPAB 347 Rathore Int. J. Pure App. Biosci. 6 (5): 346-354 (2018) ISSN: 2320 – 7051 R. reniformis where large number of host observed that R. reniformis preferred species grouped in much less number of dicotyledons and results of the present study genera, families and orders. R reniformis are in agreement of observations of these followed the same trend as was depicted for authors. Robbinson et al.16 expressed his combined description of all the species of dissent because more dicot plants are present Rotylenchulus. The major contribution in the in nature as compared to monocots. It may be host range of R. reniformis was of febids more useful if explanation is restricted to our (20.840%) and malvids (14.625%) followed observations i.e. host range of the nematodes by monocots (commelinids) (15.539%), in general and/or of any particular species. lamiids (8.592%) and campanulids (7.861%). Similarly, there is a point of disagreement for In addition to that R. parvus and R. reniformis a reported host plant. It would be better if it also hosted on one each gymnosperm plants of retested in the same locality and on the species family Cupressaceae and Cycadaceae, it was reported earlier as a host. Ecological respectively. conditions and host cultivar or variety would Host plants in some families invited undoubtedly play a great role in deciding the more than one Rotylenchulus species. The acceptability. Variation could also be due to greater affinity was exhibited by seven different pathotypes or races prevailing in Rotylenchulus species to host plants in different ecosystems. Dasgupta and Seshadri4 Poaceae, followed by 6 in Fabaceae and reported occurrence of two races (Race-A and Malvaceae and four each in Asteraceae, Race-B) in India. Arias et al. 2 and Leach et Oleaceae and Solanaceae (Table 4). al.8 demonstrated genetic variability in R. Hutchinson7 divided dicotyledons in reniformis populations using microsatellite lignosae (trees and shrubs-a fundamentally markers suggesting that the pathogenic woody group) and herbaceae (herbs or rarely population of R. reniformis could be another shrubs-a fundamentally herbaceous group). species. For discussion, when families of all the host Molecular characterization of six valid plants of Rotylenchulus species were placed in known species of Rotylenchulus viz., R. lignosae and herbaceae divisions, it was clavicaudus, R. leptus, R. macrodoratus, R. observed that about 60% of plant species fell macrosoma, R. reniformis and R. sacchari in lignosae. This suggests that Rotylenchulus revealed that R. reniformis and R. macrosoma species prefer woody plants as their hosts have sister relationship, but that relationship except the ones which are monophagous on between other species remain unresolved 17. In monocotyledons. our study, however, R. macrosoma had very Gaur et al.6 reported that host range of few host species (only eight), whereas R.