|Keywords (Extracted from title, table of contents and abstract of thesis)
sapodilla, achras zapot l., hemicriconemodies mangiferae siddiqi, nematodes, longidorus, paratylenchus, rotylenchus, trichodorus, tylenchulus, xiphinema, macroposthonia, helicotylenchus indicus, h multicinctus, hoplolaimus columbus, psilenchus hilarus, rotylenchulus reniformis, tylenchorhynchus martini
Of. the 20 genera of stylet-bearing nematodes recovered from around the roots of 33 plant species in Karachi district, Longidorus, paratylenchus, Rotylenchus, Trichodorus, Tylenchulus and Xiphinema are new reports from this area whereas Macroposthonia is entirely new for Pakistan. Out of the several species found associated with sapodilla (Achras zapota L.,), Helicotylenchus indicus, H multicinctus, Hoplolaimus Columbus, Psilenchus hilarus, Rotylenchulus reniformis, and Tylenchorhynchus martini are new records for Pakistan. In addition, the association of Hemicricenemoides mangiferae Siddiqi, 1961 with 10 plants is reported. first time. H mangiferae was the most frequently encountered species associated with sapodilla, followed by Paratylenchus spp. (including .P. curvitatus group Geraert, 1965), Helicotylenchus spp. (including H. indicus Siddiqi, 1963), and Xiphinema americanum Cobb, 1913. M. mangiferae and other nematodes around sapodilla roots showed 2 seasonal peaks, One in March-April and the other in October-November. A soil temperature of 19-220C and moisture of 12-16%. appeared favorable for nematodes, and these two factors were considered important for population changes in this area. Vertical and horizontal distribution of stylet-bearing nematodes was found correlated with sapodilla roots. H. mangiferae was concentrated at e depth of 9-18 in. and upto a horizontal distance of 18 in. Psilenchus hilarus Siddiqi, 1963 and no-stylet-bearing forms were common in. upper zones where few or no roots were present.
Of the 23 species of plants tested, sapodilla, Mangiferae. indica, Mimusops hexandra, Tamarindus indica, Carica Papaya, Gossypium hirsutum, Psidium guajava, Saccharum officinarum and Grewia asiatica were found as houts of H. mangiferae whereas Musa. sapientum, Brassica oleracea var. botrytis, Hibiscus ,esculentu, Allium Cepa, Brassica rapa, Capsicum frutescence Citrus sinensis. Coriandrum sativum, Daucus Carote, Beta vulltaris, Lycopersicon esculentum. Pisum sativum. Raphanus sativa and Solanum melongena were non-hosts. No survivors were recovered in fallow controls. Helicotylenchus indicus and Paratylenchus spp. also reproduced on sapodilla. H mangiferae, was ectoparasitic and found pathogenic to sapodilla. minusops hexandra. Mangiferae indica. and Tamarindus indica @6 nemas/ml. soil and was non-pathogenic to Psidium suajava. Gossypium and Capsicum frutescence at hirsutum, musa sapientum this inculum potential.
In pot experiments. H. mangiferae thrived best at a soil moisture level of 1596. Addition of sand to the natural soil. favoured nematodes but the addition of ,clay had an adverse effect.
In the presence of H. mangiferae, Rhizoctonia bataticola was more active in producing wilting of cotton plants as compared to Fusarium oxysporum. In another' experiment., Helicotylenchus indicus was found a better competitor than H. mangiferae or Paratylenchus spp.
Nematode population was significantly reduced by the pre- and post-plantation treatment of soil with Nemagon (1,2-dibromo-3-chloropropane) but no difference in the growth or yield of plants was noted. However, in pot experiment, Nemagon @ 0.75 and 1.50 ml./pot was found to control H. mangiferae and to cause significant increase in top and root growth.