Thávio Júnior Barbosa Pinto

Summary: The root-knot nematode, Meloidogyne enterolobii, is an important pathogen of numerous crops, including the so-called pulses. Hence, it is necessary to identify genetic resistance, as it is the most efficient, cost-effective, and environmentally sound way to manage nematodes in the field. The objective of this study was to screen a Brazilian germplasm collection of pulse crops (peas, chickpeas, and lentils) comprising accessions from the Embrapa Germplasm Bank and commercial cultivars against M. enterolobii under glasshouse conditions. The experiment was conducted with 23 treatments (genotypes), i.e., 14 pea, six chickpea and one lentil genotype, and two tomato cultivars, ‘Rutgers’ (susceptible) and ‘Nemadoro’ (resistant). Each plant (replication) was inoculated with 5000 eggs and second-stage juveniles (J2) of M. enterolobii and evaluated 65 days after inoculation, considering the following variables: gall index, egg mass index, number of eggs per g of roots, and reproduction factor. The experiments were conducted at two independent time points (summer and autumn/winter). Results showed that all 23 plant genotypes were susceptible to the nematode, with pea genotype ‘Itapuã’ being intolerant to infection. Cultivation of pulse crops has been steadily increasing both in Brazil and worldwide. Our research findings make a valuable contribution to the ongoing efforts to identify genetic resistance to nematode pathogens that can significantly affect the productivity of these crops. By identifying and developing resistant genotypes, pulse crop yields can be safeguarded, and sustainable agricultural practices can be supported.

The objective of this work was to verify the reaction of potato clones and cultivars to root-knot nematodes in a field area naturally infested by the root-knot nematodes Meloidogyne incognita and M. ethiopica. Fifteen clones and five potato cultivars were evaluated, in addition to plots with okra and tomato susceptible species, in a field naturally infested with a Meloidogyne incognita and M. ethiopica population mixture, in an experimental field of Embrapa Hortaliças located in the Federal District, Brazil. The experiment was carried out from April to August 2022, in a randomized complete block design with four replications of five plants per plot. At the planting time, as well as when harvesting the genotypes, soil was collected to determine the initial and final nematode populations. When the plants were harvested, the total number of juveniles extracted from plant tissues (potato tubers and okra roots and tomato) was determined, as well as the calculation of the reproduction factor (RF), and the evaluation of tuber yield of the potato genotypes. Data were submitted to analysis of variance and grouping of means by the Scott-Knott test. The clones C2743-09-09, CH41, F119-12-01, F129-12-08, F63-10-13A, F65-13-06, F88-11-01 and OD38-06, and the cultivars Markies, Agata and Asterix were the least susceptible genotypes to field mix of the root-knot nematodes M. incognita and M. ethiopica. But combining a lower degree of susceptibility and good tuber productivity, clones MB54-02, F53-11-05, F63-10-13A, F65-13-06, OD38-06 stood out. The commercial cultivars Atlantic and Epagri Catucha presented greater multiplication of nematodes in the field than the other evaluated cultivars.

The root-knot nematode (RKN) Meloidogyne enterolobii is gaining importance all around the world, including Brazil, damaging sweetpotato genotypes with known resistance to other RKN species, making it challenging to generate new resistant genes. This study aimed to assess the levels of resistance of 10 advanced sweetpotato cultivars to this nematode species. Two experiments were carried out in 2018/2019 and 2021/2022 seasons, under greenhouse conditions in Brasília-DF, Brazil. A completely randomized block design with six replicates of one plant/plot/treatment was used. The gall index (GI) and egg mass index (EMI) in the root system of each plant, the number of eggs and juveniles per gram of root with galls (NERG), and the nematode reproduction factor (RF) were determined. M. enterolobii resistance is present within three of the evaluated clones: BGBD 1399, MD 1609024, and MD 1610036, therefore demonstrating their potential as sources of resistance genes to assist breeding efforts to release cultivars, and help to reduce the impact and spread of this RKN.