Possible causes of yield failure in tropical aerobic rice

The potential phytosanitary importance of all named plant-parasitic nematode species was determined by evaluating available information on species characteristics, association with economically-important crop hosts, and ability to act as vectors of viruses or form disease complexes with other pathogens. Most named species of plant-parasitic nematodes (PPN) are poorly known, recorded from a single location only, not associated with economically-important crops, and not known to be associated with other plant disease organisms. However, 250 species from 43 genera fulfilled one or more of the criteria to be considered to present a phytosanitary risk. The genera and number of species (in parentheses) considered as posing phytosanitary risk included: Achlysiella (1), Anguina (8), Aphasmatylenchus (1), Aphelenchoides (12), Aphelenchus (1), Belonolaimus (2), Bitylenchus (3), Bursaphelenchus (4), Cactodera (3), Ditylenchus (8), Dolichodorus (1), Globodera (3), Helicotylenchus (7), Hemicriconemoides (3), Hemicycliophora (3), Heterodera (25), Hirschmanniella (5), Hoplolaimus (5), Ibipora (3), Longidorus (10), Macroposthonia (2), Meloidogyne (38), Merlinius (3), Nacobbus (1), Neodolichodorus (2), Paralongidorus (2), Paratrichodorus (11), Paratylenchus (3), Pratylenchus (24), Punctodera (3), Quinisulcius (3), Radopholus (5), Rotylenchulus (3), Rotylenchus (1), Scutellonema (5), Sphaeronema (1), Subanguina (3), Trichodorus (5), Tylenchorhynchus (8), Tylenchulus (2), Vittatidera (1), Xiphinema (15) and Zygotylenchus (1). For each of the 250 species main hosts and yield loss estimates are provided with an extensive bibliography. Of the 250 species, only 126 species from 33 genera are currently listed as regulated pests in one or more countries worldwide. Almost all of these 250 species were also associated with economically important crops and some also acted as vectors for viruses. © 2013 The Authors. Journal compilation

Plant-parasitic nematodes of potential phytosanitary importance, their main hosts and reported yield losses

Biotic and abiotic causes of yield failure in tropical aerobic rice.

Sununary - Effects of Meloidogyne graminicola and nitrogen applications on growth and yield of upland rice cultivar UPL Ri-5 were studied in two glasshouse experiments. Plant height, shoot weight, I.eaf area, root weight, depth of rooting, and number of panicles and grains were reduced by the nematode. Grain yield was reduced by 30-70 % when the number of infective juveniles present around young seedlings at transplanting (Pi) was ~ 375. Total nitrogen in shoots decreased by 10-31 % at maximum tiUering and by 14-20 % at flowering when 375 ~ Pi ~ 7500. Nitrogen concentration in shoots was not reduced. Root nitrogen concentra­ tion increased by 70-140 % at flowering and by 101-145 % at maturiry with 375 ~ Pi ~ 7500. The nitrogen concentration in roots was positively correlated with Pi and the number of juveniles recovered from the rOOts. Nitrogen application increased growth and yield whether plants were infested by the nematode or not. However, because the percentage of yield loss remained approximately constant for a given Pi across the range of nitrogen quantities applied, nitrogen applications did not reduce the relative nematode effect.

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The potential of increased nitrogen supply to mitigate growth and Yield reductions of upland rice cultivar UPL Ri-5 caused by Meloidogyne graminicola (I)

During the present investigation the nutritional quality of underground vegetables infected by root-knot nematode (Meloidogyne incognita) was evaluated. It was observed that physiological and biochemical changes occurred due to the invasion of root-knot nematodes in the studied vegetables. Results show that there was a significant difference in root-knot development and reproduction in infected and un-infected host plants. Data indicates that highest reproduction rate and rootknot index was observed in vegetable plants infected with root-knot nematodes after three months as compared to un-infected (control). The physiological parameters as well as biochemical contents showed significant difference in different growth criteria and amount of nutrients between infected host plants as compared to un-infected plants (control). Growth parameters of studied vegetable plants viz., fresh and dry weight and water content were decreased by the infection of root-knot nematode as compared to un-infected (control) plants. Similarly root-knot nematode decreased the host nutrients contents viz., total carbohydrates, total soluble sugars, total protein, total phenols and amino acids. Chlorophyll a, chlorophyll b and carotenoids also decreased in nematode infected plants as compared to control. This study gave the fair report towards nutritional quality because no significant work has been done so far on this aspect in Pakistan.

Impact Of Nematode Infestation on Nutritional Quality of Some Underground Vegetables in Pakistan

SUMMARY Infestation of rice by Heterodera o yzicola and Mebidogyne grantinicola caused reduction in nitrogen, phosphorus, iron, and reducing sugars in shoots and roots. Total sugars, protein, IAA, cytokinin and thiamine were reduced in the cyst nematode infested plants and phenols were reduced with root-hot nematode infested plants. Phenols decreased in shoots and increased in roots due to cyst nematode, while the rootknot nematode caused similar changes in potassium, manganese and magnesium. There was an increase in calcium, sodium, soluble amino-acids, ABA and starch in both shoots and roots of the cyst nematode infested plants and of total sugars, protein, DNA and RNA with the root-knot nematode infested plants. Infestation by both the nematodes caused nutritional disorders limiting the uptake of nitrogen and phosphorus and chlorosis of leaves.

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_5/pt5/nemato/27728.pdf

A. Jayaprakash

Papers

Nutritional disorders in rice due to infestation by Heterodera oryzicola and Meloidogyne graminicola.