Antonia Thalyta Lopes Silveira

The tomato (Solanum lycopersicum L.) is one of the most important vegetables from an economic, social, and nutritional point of view, being widely consumed throughout the world, both fresh and processed. Due to its importance, this crop is a constant focus of genetic improvement programs that seek to develop superior genotypes, such as higher quality, yield, and disease resistance. Thus, the aim of this study was to select experimental indeterminate Italian tomato hybrids with high yield, superior fruit quality, and resistance to TSWV (tomato spotted wilt virus) via molecular markers. The trial was conducted in the municipality of Ijaci, southern Minas Gerais, Brazil. A randomized block design was used, with 16 hybrids (12 experimental and 4 commercial controls), four replications, and five plants per plot. Evaluations were carried out for yield, fruit quality, and resistance to TSWV under natural infection and through molecular markers to identify the Sw5 gene. Six experimental hybrids stood out in terms of high yield, with hybrid TO-014 being superior to the others, presenting better size and higher commercial classification. Most genotypes showed few defects, revealing good qualitative characteristics, with the exception of three hybrids (TO-004, TO-042, and TO-134), which demonstrated greater susceptibility to TSWV. Seven experimental hybrids were considered resistant to TSWV because they carry the Sw-5 gene and did not show symptoms of infection in the field. Six of these hybrids also stood out in terms of yield and fruit quality, demonstrating that resistance to the virus has a direct impact on productive characteristics.

Banana bunchy top virus (BBTV) has been recently recorded in Mozambique and threatens economic viability of banana production in this country. Research on BBTV in the region is still initial, and collective effort is required to support efficient control measures. Surveys were made in four administrative areas of the Chóckwè district, Gaza Province, to determine the incidence and distribution of the virus. Samples were collected from two banana cultivars in 23 production fields where the plants had characteristic virus symptoms. DNA was extracted from these samples and subjected to BBTV detection using polymerase chain reaction technology. BBTV was detected in 19 of the 23 sampled fields, with overall mean incidence of 54.3%, and minimum incidence of 20%. No infected plants were found in the fields of one farm. These results highlight the urgency to initiate strategies for control of BBTV in Mozambique.

The Alto Paranaíba region, located in Minas Gerais State, Brazil, is one of the largest garlic producers in Brazil, but little is known about the occurrence and incidence of viral diseases in the region. In this study, a survey of the viral species presents in 10 areas in the municipality of São Gotardo. Each sampled area was divided into 3 subareas, and in each subarea, 1290 plants were visually evaluated for the presence or absence of symptoms and 25 leaves each with and without symptoms were collected to identify the viruses present by means of RT‒PCR. The incidence of viruses in the ten areas was quite variable, and four of them had a lower incidence, ranging from 2.9–16.7%. Two of the others presented incidences of 42.9% and 86.4%, while four showed an incidence of 100%. The infected plants showed an aggregated spatial distribution pattern in 90% in the run test and a random distribution in 63.3% in the doublet test. The dispersion index in 63.3% of the blocks indicated a regular spatial pattern. All symptomatic samples collected were positive for the presence of one or more virus species belonging to the genera Potyvirus, Carlavirus and Allexivirus, indicating possible transmission by the cloves used in planting. These results demonstrate the importance of vector control and the use of virus-free propagation material because the presence of the inoculum at the beginning of the crop cycle means a longer time for dissemination and impairment of productivity.

Banana bunchy top virus (BBTV) was recently detected in Mozambique and appears to be limited to the provinces of Gaza, Maputo and Zambezia, but it has great potential to spread to other provinces. Despite its importance, nothing is known about the BBTV isolates that occur in Mozambique. In this study, the sequences of the S and R genes of forty isolates chosen as representatives of samples collected previously from eleven farms of the four administrative posts of the district of Chóckwè, province of Gaza, were sequenced and analyzed. The S-DNA nucleotide sequences of the analyzed isolates were highly conserved, with identity ranging from 97% to 100%. The same was observed for the R-DNA sequences, with most identities ranging between 98% and 100% among the isolates from Chókwè and above 90% when compared to the isolates from GenBank. The phylogenetic analysis showed that the Mozambican BBTV isolates belong to the Pacific–Indian Oceans (PIO) group, showing greater proximity to the isolate JQ820453 from Malawi than to the isolates from sub-Saharan countries, which were grouped in a distinct subclade. This is the first study conducted to determine the molecular characteristics of BBTV isolates present in Mozambique.

Banana bunchy top virus (BBTV) was recently detected in Mozambique and appears to be limited to the provinces of Gaza, Maputo and Zambezia, but it has great potential to spread to other provinces. Despite its importance, nothing is known about the BBTV isolates that occur in Mozambique. In this study, the sequences of the S and R genes of 40 isolates chosen as representatives of samples collected previously from eleven farms of the four administrative posts of the district of Chóckwè, Gaza province, were sequenced and analyzed. The S-DNA nucleotide sequences of the analyzed isolates were highly conserved, with identity ranging from 97% to 100%. The same was observed for the R-DNA sequences, with most identities ranging between 98% and 100% among the isolates from Chókwè and above 90% when compared to the isolates from GenBank. The phylogenetic analysis showed that the Mozambican BBTV isolates belong to the Pacific-Indian Oceans (PIO) group, showing greater proximity to the isolate JQ820453 from Malawi than to the isolates from sub-Saharan countries, which were grouped in a distinct subclade. This is the first study conducted to determine the molecular characteristics of BBTV isolates present in Mozambique.

Treatments with pyraclostrobin, a fungicide from the strobilurin chemical group, have induced physiological effects in several plants, which may influence their productivity. In this study, two experiments were carried out to study the effect of a commercial product containing pyraclostrobin + metiram on productivity and virus dissemination in potato cultivars. The first experiment was carried out in Maria da Fé-MG, applying different combinations of the product via furrow at planting and via foliar application, in post-emergence, using the cultivar Cupido and two fertilizer levels: 2,500 kg/ha and 3,500 kg/ha of NPK in the formulation 4:14:8. In the second experiment, eight French potato cultivars were tested in São Gonçalo do Sapucaí-MG, with applications of the fungicide via furrow and via foliar application. An interaction between the fertilizers and cultivars with the types of fungicide treatments used was observed. There was a significant increase of 13.6% in the production of the treated potato cv. Cupido, when the fungicide was applied in the furrow and the NPK level was 2,500 kg/ha. The production of all eight cultivars tested was higher in the treated plots, and the greatest productivity gain was 28% in cv. Eole. In both experiments, pyraclostrobin did not affect the spread of the virus in the field. This study showed that pyraclostrobin has the potential to increase potato productivity and reduce fertilizer use. However, the best treatment and the best fertilizer level should be determined for each cultivar, since the cultivars used responded differently to the same treatments.

Potato virus Y (PVY) is recognized as one of the most common and destructive pathogens seriously affecting potato producing areas worldwide. More recently PVY^NTN and PVY^N:O/N-Wi, have emerged as the main strains present in the PVY infected plants detected in Brazilian potato fields. In this study, samples of potato collected in south part of Minas Gerais - Brazil were first tested by DAS-ELISA and then by RT-PCR multiplex in order to discriminate the PVY strains. Afterward, part of them was tested by RT-qPCR to confirm and quantify the viruses in infected tissues. The sensitivity of the techniques for detecting PVY isolates present in the sampled locations was investigated, as well as the occurrence of mixed infections, aiming to understand the general epidemiological picture of this pathogen in potato producing fields. In the multiplex RT-PCR test, the samples with O and N serotypes were identified as infected with PVY^NTN and PVY^N:O/N-Wi strains. When tested by RT-PCR for amplification of PVY^E, 41 samples (67,2%) were positive, having a characteristic electrophoretic profile for this recombinant strain, and 9 isolates were also observed with atypical patterns for recombinant PVYE. The best technique to detect mixed infection was RT-qPCR, with the concentration of PVYNTN being much higher than that of PVYN:O/N-Wi. These results show the importance of using the most suitable method for the diagnosis and surveying of PVY strains in crop fields and reveal, for the first time, the dissemination of PVYE recombinants to several Brazilian potato fields.