SlWRKY45 Interacts with Jasmonate-ZIM Domain Proteins to Negatively Regulate Defense Against Root Knot Nematode Meloidogyne incognita in Tomato

Root knot nematode (RKN), a kind of plant parasitic nematodes, leads to large reduction of crop yield, and seriously damages the agricultural production. The phytohormone jasmonates (JAs) act as important signals to regulate resistance against multiple abiotic and biotic stresses. However, little is known about the mechanism of JA-mediated defense responses against RKN in tomato. In this study, we found that the WRKY transcription factor SlWRKY45 interacts with most of the Jasmonate-ZIM domain proteins (JAZs) in yeast and plant. Overexpression of SlWRKY45 decreased plant resistance to RKN Meloidogyne incognita with increased gall index. We further generated slwrky45 mutants using the CRISPR/Cas9 technology, and discovered that the gall index and the number of nematodes and females in slwrky45 mutants are significantly reduced compared with wild type, as inoculated with RKN Meloidogyne incognita. Moreover, the contents of jasmonic acid and JA-isoleucine (JA-Ile) were highly increased in slwrky45 mutants with RKN Meloidogyne incognita infection compared with wild type. Furthermore, EMSA, and Dual-LUC assays demonstrated that SlWRKY45 directly binds and represses jasmonate biosynthesis gene ALLENE OXIDE CYCLASE ( AOC). Overall, our findings reveled that JAZ-interaction protein SlWRKY45 negatively controls plant defense against RKN Meloidogyne incognita by the regulation of JA biosynthesis in tomato.

IDENTIFICATION OF SOURCES OF RESISTANCE TO Meloidogyne enterolobii IN ACEROLA1

ABSTRACT In Brazil, acerola trees infested by Meloidogyne enterolobii present lower yield and fruit quality. The use of rootstocks resistant to this pathogen is one of the alternatives to overcome this problem. This study aimed to assess the reaction of 22 acerola accessions to M. enterolobii, aiming to identify at least one resistant rootstock. The experiment was carried out in a randomized block design with 10 replications and each plot consisting of 10 plants. Each plant was inoculated with 350 eggs and second-stage juveniles of M. enterolobii, with the gall index (GI) and reproduction factor (RF) being determined after 90 days. The variables were analyzed using the mixed model methodology (REML/BLUP). The accessions ACO-13, ACO-14, ACO-18, and BRS Apodi stood out with four to six plants showing resistance reaction to the root-knot nematode, but the assessment of accessions should be performed under a higher density inoculum and longer time.

Inoculum Level and Inoculation Method Influences on the Pathogenic Activities of Meloidogyne incognita in Studied Model Plant Okra (Abelmoschus esculentus L. Moench)

Agricultural activities such as watering crops with nematode-infested water from wells and boreholes, and using infected plant debris as manure or mulch increase root-knot nematode infection. So, this study aims at assessing the influence of the inoculation method and inoculum level of Meloidogyne incognita on the development of root galls on okra plants. Two M. incognita inoculation methods (suspension of individuals and galled root explants) and six inoculum levels (0, 10, 100, 500, 1000 and 2000 second-stage larvae/plant) were studied. The gall index, total numbers and reproductive factor of M. incognita were used to assess the effect of treatments on root gall development. Unlike the reproductive factor, gall index and the total numbers of M. incognita increased with their inoculum level. The pathogenic activities of M. incognita were most significant when crop soils were infested with galled root explants. However, an inverse relationship was found between the inoculum levels of M. incognita and the okra plant’s development. It is reflected by negative correlation coefficients ranging from -0.90 to -0.62. It is therefore important to burn roots infected with root-knot nematodes left in fields so that they do not act as an inoculum for crops.

Microorganisms in the biological control of root-knot nematode: A metanalytical study

Nematodes can cause annual losses in the order of 100 billion dollars in crops worldwide. Its control using chemical nematicides proves to be quite aggressive to the environment. For this reason, the management of microorganisms has been promising. However, it is essential to know the control potential of each organism. Thus, the objective of this study was to verify the efficiency of different microorganisms in the biological control of Meloidogyne sp. A systematic review of the literature was carried out from 2000 to 2020 with the keywords “Meloidogyne and biology control", resulting in 659 articles, of which 51 were pre-selected and, after the more detailed evaluation, was selected ten published articles. These ten articles generated a total of 83 studies for meta-analyses. Each study included a treatment group using some microorganisms (bacteria, fungus, actinomycetes) for nematode biocontrol, a control group without using biocontrol agents. From this meta-analysis, we can observe that the use of microorganisms decreased the number of galls (42.05%), the number of eggs (57.77%), the gall index (28.58%) and the eggs mass (53.48%). The use of microorganisms was also positive in increasing root mass (832.89%). We can conclude that the use of microorganisms proved to be efficient in controlling nematodes M. javanica and M. incognita. The fungi Pleurotus ostreatus and Phanerochaete chrysosporium have more significant potential for biocontrol for these species.

Respuesta del perejil crespo a diferentes densidades de población de Meloidogyne arenaria

The effect of initial population density (Pi) of the peanut root-knot nematode, Melodoigyne arenaria, on curly leaf parsley growth was assessed in this study. The population densities of M. arenaria ranged from 0 to 64 eggs + second-stage juveniles (J2)/cm3 soil in sterile sandbags. The root gall index (RGI), reproduction factor (RF), fresh leaf weight (FLW), dry leaf weight (DLW), root fresh weight (RFW), root length (RL), leaf height (LH), and chlorophyll index (SPAD) were determined at 90 days after inoculation. FLW, DLW, RFW, LH, and SPAD data were fitted to the Seinhorst equation, y = m + (1 - m) zPi-T, to determine the tolerance limit T = 0.25 eggs +J2/cm3 soil for FLW, DLW, RFW, and LH, with relative means (m) of 0.52, 0.24, 0.22, and 0.4 respectively; conversely, the T value for SPAD was 0.125 eggs + J2/cm3 soil and with a m of 0.26. All biometric variables decreased with an increase in the initial population density (Pi). Nevertheless, the highest RF of M. arenaria in parsley was 78.92 for a Pi = 8 eggs + J2/cm3 soil, with an RGI value of 5 from Pi = 1 eggs + J2/cm3. Curly leaf parsley growth decreased with an increase in Pi of M. arenaria.

Estimating numbers.

Estimating nematode numbers is required to quantify the presence of certain nematode taxa in plant tissue, field soil or any other substrates. This chapter describes the enumeration of nematodes within plant tissue (e.g. roots, stems, leaves, seeds) and in liquids. It also deals with estimating numbers of cysts; eggs and juveniles isolated from cysts; gall index; and egg masses.

Parasitism of Meloidogyne exigua races 1 and 2 in coffee plants derived from Timor Hybrid

ABSTRACT: To investigate the degree of parasitism of two populations of Meloidogyne exigua, the gall index (GI) and the reproduction factor (RF) of M. exigua races 1 (Est E2) and 2 (Est E1) were analyzed in 47 progenies on F3:4 or F4:5 generation derived from the crossing between Coffea arabica cv. Catuaí Amarelo and Timor Hybrid. C. canephora cv. Apoatã IAC 2258 and C. arabica cv. Catuaí Vermelho IAC 144 were used as resistance and susceptibility checks, respectively. The genotypes that were classified as resistant or susceptible by RF were similarly classified by GI, showing a close relationship between both methodologies. The data also indicated no differences in virulence between the nematode populations, since the progenies showed similar resistance reactions to the M. exigua races 1 and 2. According to GI from the 47 mother plants evaluated, 27 progenies (57.4%) were classified as resistant to M. exigua races 1 and 2, with GI ranging from 0.0 to 1.4 and 20 progenies (42.6%) were susceptible with GI from 2.6 to 4.4. These results showed that most of the evaluated germplasm was very promising in relation to the development of new Arabica coffee cultivars with resistance to M. exigua.

Estimating numbers.

Estimating nematode numbers is required to quantify the presence of certain nematode taxa in plant tissue, field soil or any other substrates. This chapter describes the enumeration of nematodes within plant tissue (e.g. roots, stems, leaves, seeds) and in liquids. It also deals with estimating numbers of cysts; eggs and juveniles isolated from cysts; gall index; and egg masses.

Evaluation of Host Plant Resistance to Meloidogyne incognita in Banana Hybrids

The reaction of twenty four new synthetic banana hybrids were selected and evaluated for resistance to M. incognita under artificially inoculated pot conditions. Known susceptible (Grand Naine) and resistant (Yankambi KM5) banana varieties were included as reference cultivars. Responses of banana hybrids to M. incognita infection was assessed by the nematodes population in roots, number of galled roots, percentage of galled roots and root gall index on a scale of 1-5, where 0 = 0 galls and 5≥100 galls. The result showed that seven banana hybrids, H 904, H 911, H 921, H 924, H 926, H 943 and H 952 were found to be tolerance to M. incognita and the remaining were rated as moderate susceptible and susceptible. The total phenols, peroxidase, polyphenol oxidase, phenylalanine ammonia lyase chemical and enzyme contains in roots were higher in tolerance genotypes viz-a-vis susceptible ones.

Trichoderma asperellum affects Meloidogyne incognita infestation and development in Celosia argentea

Due to the rise in cost and detrimental health and environmental consequences that accompany the use of nematicides, there is a need for a more eco-friendly and less expensive alternative to control root-knot nematode (Meloidogyne incognita). Nematode infestation reduces the quality and quantity of Celosia argentea Linn. A pot experiment was conducted in a greenhouse to determine the biocontrol efficacy of Trichoderma asperellum against M. incognita in C. argentea. The treatments consisted M. incognita infected C. argentea inoculated with 0, 2.2 × 107, 4.4 × 107, or 6.6 × 107 cfu/pot of T. asperellum. All doses of T. asperellum reduced the root-knot nematode population and root gall index. Growth and development of C. argentea were improved, indicating that T. asperellum has the potential to be used as a biocontrol agent in C. argentea production. The biocontrol activity of T. asperellum in C. argantea increased as the week went by until the plants attained full maturity. Hence, the control of M. incognita by T. asperellum depends on the developmental stage of the plant root system.