Genome assembly of two nematode-resistant cotton lines (Gossypium hirsutum L.)

Upland cotton (Gossypium hirsutum L.) is susceptible to damage by the root-knot and the reniform nematodes, causing yield losses greater than 4% annually in the U.S. Additionally, these nematodes are synergistic with seeding disease and root rot pathogens that exacerbate diseases and subsequent yield losses. Production practices to minimize nematode damage include crop rotation and nematicides, but these techniques need to be repeated and are expensive. The use of resistant cultivars is deemed the most effective and economical approach for managing nematodes in cotton. Here we describe the genomes of two nematode-resistant lines of cotton, BARBREN-713 and BAR 32-30. These genomes may expedite the development of DNA markers that can be used to efficiently introduce nematode resistance into commercially valuable Upland lines.

Characterizing Repeats in Two Whole-Genome Amplification Methods in the Reniform Nematode Genome

One of the major problems in the U.S. and global cotton production is the damage caused by the reniform nematode, Rotylenchulus reniformis. Amplification of DNA from single nematodes for further molecular analysis can be challenging sometimes. In this research, two whole-genome amplification (WGA) methods were evaluated for their efficiencies in DNA amplification from a single reniform nematode. The WGA was carried out using both REPLI-g Mini and Midi kits, and the GenomePlex single cell whole-genome amplification kit. Sequence analysis produced 4 Mb and 12 Mb of genomic sequences for the reniform nematode using REPLI-g and SIGMA libraries. These sequences were assembled into 28,784 and 24,508 contigs, respectively, for REPLI-g and SIGMA libraries. The highest repeats in both libraries were of low complexity, and the lowest for the REPLI-g library were for satellites and for the SIGMA library, RTE/BOV-B. The same kind of repeats were observed for both libraries; however, the SIGMA library had four other repeat elements (Penelope (long interspersed nucleotide element (LINE)), RTE/BOV-B (LINE), PiggyBac, and Mirage/P-element/Transib), which were not seen in the REPLI-g library. DNA transposons were also found in both libraries. Both reniform nematode 18S rRNA variants (RN_VAR1 and RN_VAR2) could easily be identified in both libraries. This research has therefore demonstrated the ability of using both WGA methods, in amplification of gDNA isolated from single reniform nematodes.

Root-knot and reniform nematodes: double trouble for soybeans in the southern United States.

This chapter focuses on the economic importance, host range, geographical distribution, symptoms of damage and biology and life cycle of root-knot and reniform nematodes (Meloidogyne spp. and Rotylenchulus reniformis) infesting soyabeans in southern USA. Some information on the efficacy and optimization of some recommended integrated nematode management practices and future outlook and research requirements are also presented.

Rotylenchulidae: Rotylenchulus species.

The reniform nematodes of the genus Rotylenchulus are sedentary and semi-endoparasites of plants. This chapter includes information on: authentic identification; geographical distribution; risk of introduction; host ranges; symptoms; biology and ecology; planting material liable to carry the nematode; chance of establishment; likely impact; phytosanitary measures; and a detailed account of diagnosis procedures, such as sampling, isolation/detection and identification with morphological and molecular characterization, of invasive Rotylenchulus species.

BIOMANAGEMENT OF ROOT-KNOT AND RENIFORM NEMATODES ON OKRA

Seed dressing with culture filtrate of Paecilomyces lilacinus resulted in a significant control of root-knot nematodes, Meloidogyne incognita and reniform nematode, Rotylenchulus reniformis singly or concomitantly, with a corresponding increase in plant growth, length and weight of plants and number of pods, chlorophyll content of leaves, water absorption capacity of roots of okra (Abelmoschus esculentus). In another experiment soil application with oil cake of neem (Azadirachta indica) showed significant suppression of the nematodes, both singly as well as concomitantly, with the consequent improvement in different growth parameters of the plants as above. A combination of seed dressing treatment with culture filtrate of P. lilacinus and soil amendment with neem cake gave synergistic effect with respect to nematode management and improvement in plant growth parameters.

Global Distribution of the Reniform Nematode Genus Rotylenchulus with the Synonymy of Rotylenchulus macrosoma with Rotylenchulus borealis

Reniform nematodes of the genus Rotylenchulus are semi-endoparasites of numerous herbaceous and woody plant roots that occur largely in regions with temperate, subtropical, and tropical climates. In this study, we compared 12 populations of Rotylenchulusborealis and 16 populations of Rotylenchulusmacrosoma, including paratypes deposited in nematode collections, confirming that morphological characters between both nematode species do not support their separation. In addition, analysis of molecular markers using nuclear ribosomal DNA (28S, ITS1) and mitochondrial DNA (coxI) genes, as well as phylogenetic approaches, confirmed the synonymy of R. macrosoma with R. borealis. This study also demonstrated that R. borealis (= macrosoma) from Israel has two distinct rRNA gene types in the genome, specifically the two types of D2-D3 (A and B). We provide a global geographical distribution of the genus Rotylenchulus. The two major pathogenic species (Rotylenchulusreniformis and Rotylenchulusparvus) showed their close relationship with warmer areas with high annual mean temperature, maximum temperature of the warmest month, and minimum temperature of the coldest month. The present study confirms the extraordinary morphological and molecular diversity of R. borealis in Europe, Africa, and the Middle East and comprises a paradigmatic example of remarkable flexibility of ecological requirements within reniform nematodes.

New distribution and molecular diversity of the reniform nematode Rotylenchulus macrosoma Dasgupta, Raski and Sher, 1968 (Nematoda: Rotylenchulinae) in Europe

Reniform nematodes of the genus Rotylenchulus are semiendoparasites of numerous herbaceous and woody plant roots and occur largely in regions with temperate, subtropical and tropical climates. In this study, we provide new records of the nematode R. macrosoma in eight European countries (Czech Republic, France, Germany, Hungary, Italy, Romania, Serbia and Portugal), in addition to the six Mediterranean countries (Greece, Israel, Jordan, Spain, Syria, and Turkey) where it has previously been reported. Four new host species (corn, pea, wheat and an almond-peach hybrid rootstock) are added to the recorded host species (bean, chickpea, hazelnut, peanut, soybean, wild and cultivated olive). Molecular analyses based on the coxI and D2-D3 segments of 28S RNA markers showed high diversity and pronounced genetic structure of populations of R. macrosoma. However, the complexity of phylogeographic patterns in plant-parasitic nematodes may be related to the intrinsic heterogeneity in the distribution of soil organisms, a rare occurrence of a species, or the potential human impact associated with agricultural practices.