Juan Enrique Rodríguez-Pérez

Due to the widespread distribution of F. oxysporum, the search for mechanisms of tolerance to this disease in Solanum lycopersicum L. is an ongoing endeavor. This research aimed to identify F. oxysporum-tolerant genotypes at the germination and seedling stages in order to use them as sources of resistance. Ninety-six tomato lines were inoculated with the F. oxysporum strain with NCBI accession key PQ187438. The germination test was carried out in a germination chamber at a constant temperature of 28 ± 2 °C with 70 ± 5% relative humidity in darkness for the first 3 days and then 7 days with light. Clustering and discriminant analysis identified 14 genotypes with tolerance, showing great seed vigor and lower disease severity. Seedling evaluation was conducted in a floating raft system for 10 days after inoculation. Nine genotypes showed greater tolerance to the pathogen by developing a larger leaf area and accumulating more dry matter (p ≤ 0.05). No genotypes with tolerance were identified at both phenological stages (germination and seedling), indicating that tolerance mechanisms are independent at both phenological stages, so genotype selection should be carried out independently.

High concentrations of sodium chloride (NaCl) in soil and water are increasingly common conditions in tomato (Solanum lycopersicum L.) production that impair the development and yield of this crop, generating the need for tolerant varieties. This research aimed to identify tomato lines tolerant to salinity during germination and early seedling development. A standard germination test was carried out in which 93 lines were evaluated under conditions of 0 and 80 mM NaCl for 12 days in a germination chamber with a temperature of 28 ± 1 °C and relative humidity of 80 ± 5%. At the seedling stage, 88 lines were evaluated under conditions of 0 and 150 mM NaCl in a floating raft system. During germination, saline conditions decreased germination percentage (37%), plumule (43%) and radicle (47%) length, dry matter (44%) and germination rate index (70%). At the seedling stage, NaCl decreased (p ≤ 0.05) plant height (44%) and leaf area (50%), without modifying root, aerial and total dry matter or root length. Twenty-eight tolerant lines were identified at germination and twenty-three at the seedling stage, seven of which were tolerant at both stages. This implies that salinity tolerance mechanisms differ in the developmental stages studied and makes it possible to combine these mechanisms to prolong tolerance during plant development.

Tomato is considered moderately sensitive to salinity, which detracts from the quality and yield of its fruit; therefore, wild populations have been used as a genetic resource. The aim of this research was to identify lines derived from wild tomato populations with tolerance to salinity during the germination and seedling stages. During germination, 52 wild lines and 2 commercial hybrids (Imperial^®, Reserva^®) were subjected to treatment with 150 mM and 0 mM NaCl and evaluated. The test was carried out for 20 days in a germination chamber with constant darkness, a temperature of 25 ± 2 °C and relative humidity conditions of 80 ± 4%. At the seedling stage, 22 wild tomato lines with the best performance in the germination test and 2 commercial hybrids (Imperial^®, Topanga^®) were evaluated for 12 days in a floating raft system. Concentrations of 175 mM and 0 mM of NaCl were used. During germination, the saline condition decreased the germination percentage (65.2%), speed of germination (88.2%), steam length (72.5%), root length (46.56%), number of normal plants (59.5%), stem dry matter (68.78%), root dry matter (61.99%), and total dry matter (67.1%). At the seedling stage, this condition decreased (p < 0.05) the aerial part dry matter (46.37%), leaf area (59.35%), root length (42.43%), final plant height (40.24%), and growth rate (71.42%). Seventeen tolerant genotypes were identified in one of the two developmental stages, while one genotype showed tolerance in both stages. These results indicate that there are different response mechanisms in each developmental stage. Native tomatoes play an important role in the identification of tolerant genotypes since they can be used as genetic resources for obtaining commercial genotypes with salt tolerance.

Tomato is considered moderately sensitive to salinity, which detracts from the quality and yield of its fruit; therefore, wild populations have been used as a genetic resource. The aim of this research was to identify lines derived from wild tomato populations with tolerance to salinity during the germination and seedling stages. During germination, 52 wild lines and 2 commercial hybrids (Imperial®, Reserva®) were subjected to 150 mM and 0 mM NaCl and evaluated. The test was carried out for 20 days in a germination chamber with constant darkness, temperature of 25±2 °C and relative humidity of 80±4%. At the seedling stage, 22 wild tomato lines with the best performance in the germination test and 2 commercial hybrids (Imperial®, Topanga®) were evaluated for 12 days in a floating raft system. Concentrations of 175 mM and 0 mM NaCl were used. During germination, the saline condition decreased germination percentage (65.2%), speed of germination (88.2%), steam length (72.5%), root length (46.56%), normal plants number (59.5%), stem dry matter (68.78%), root dry matter (61.99%), and total dry matter (67.1%). At the seedling stage, this condition decreased (P<0.05) the aerial part dry matter (46.37%), leaf area (59.35%), root length (42.43%), final plant height (40.24%), and growth rate (71.42%). Seventeen tolerant genotypes were identified at one of both developmental stages, while one genotype showed tolerance at both stages. These results indicate that there are different response mechanisms in each developmental stage. Native tomatoes play an important role in the identification of tolerant genotypes since they can be used as genetic resources for obtaining commercial genotypes with salt tolerance.

When a seed produced by a single-cross (SC) maize hybrid is sown, the resulting grain yield is usually lower than that of the hybrid due to the inbreeding generated. However, if a seed from a mixture of s hybrids were sown instead, the synthetic variety thus formed (Syn_SC) would have a lower inbreeding coefficient (FSyn_SC) and a higher grain yield. The grain yield s, the finite number of representatives of each parent SC (m) and the inbreeding coefficient of the parent lines of the SCs (F) are related to the FSyn_SC. In addition, randomness and the finite size of m can cause the loss of genes and genotypes and increase the FSyn_SC. The objectives of this study were to derive formulas for (1) expressing FSyn_SC in terms of m, F, and s, and (2) calculating the probability of the occurrence of gene and genotype loss. It was found that for the probability of no genotype being missing from the progeny representing a parent to be at least 0.95, it is necessary that m ≥ 15. It was also found that a sample size of 7 is sufficient for FSyn_SC to stabilize, more visibly as F is larger, and for the probability of the occurrence of erosion to be practically zero.

El chile es una especie vegetal con extensa dispersión y diversidad biológica en México, dentro de esta diversidad sobresale el chile poblano, el cual se identifica como una hortaliza muy demandada durante todo el año. En la presente investigación se realizó un análisis de crecimiento de plantas de chile poblano variedad Caballero con el objetivo de identificar las fases de crecimiento vegetal respecto a su demanda nutrimental y respuesta en rendimiento biológico. Dicho ensayo se llevó acabo en condiciones de hidroponía e invernadero, en donde se evaluaron cuatro niveles de conductividad eléctrica de la solución nutritiva de Steiner (1.0, 1.5, 2.0, 2.5 dS/m) durante 135 días después del trasplante. El rendimiento varió de 1686.0 a 2401.5 g, siendo la solución nutritiva de 2.5 dS/m la que registro el valor más alto. El área foliar fluctuó entre 6615.50 a 9535.00 cm2. A los 135 después del trasplante, la hoja fue el órgano que acumuló los valores más bajos de materia seca (48.06-68.74), mientras que el fruto fue el más alto representando más del 50 % de la materia seca total. Con la solución nutritiva a 2.5 dS/m tuvo los valores más altos en tasa absoluta de crecimiento, tasa relativa de crecimiento, tasa de asimilación neta y razón de área foliar.

Tomato (Solanum lycopersicum L.) is a vegetable with worldwide importance. Its wild or close related species are reservoirs of genes with potential use for the generation of varieties tolerant or resistant to specific biotic and abiotic factors. The objective was to determine the geographic distribution, ecological descriptors, and patterns of diversity and adaptation of 1296 accessions of native tomato from Mexico. An environmental information system was created with 21 climatic variables with a 1 km² spatial resolution. Using multivariate techniques (Principal Component Analysis, PCA; Cluster Analysis, CA) and Geographic Information Systems (GIS), the most relevant variables for accession distribution were identified, as well as the groups formed according to the environmental similarity among these. PCA determined that with the first three PCs (Principal Components), it is possible to explain 84.1% of the total variation. The most relevant information corresponded to seasonal variables of temperature and precipitation. CA revealed five statistically significant clusters. Ecological descriptors were determined and described by classifying accessions in Physiographic Provinces. Temperate climates were the most frequent among tomato accessions. Finally, the potential distribution was determined with the Maxent model with 10 replicates by cross-validation, identifying areas with a high probability of tomato presence. These results constitute a reliable source of useful information for planning accession sites collection and identifying accessions that are vulnerable or susceptible to conservation programs.

The generation of new hybrid varieties of tomato (Solanum lycopersicum L.) is the most widely used breeding method for this species and requires at least seven self-fertilization cycles to generate stable parent lines. The development of doubled haploids aims at obtaining completely homozygous lines in a single generation, although, to date, routine commercial application has not been possible in this species. In contrast, obtaining doubled haploid lines via gynogenesis has been successfully implemented in recalcitrant crops such as melon, cucumber, pumpkin, loquat and walnut. This review provides an overview of the requirements and advantages of gynogenesis as an inducer of haploidy in different agricultural crops, with the purpose of assessing the potential for its application in tomato breeding. Successful cases of gynogenesis variants involving in vitro culture of unfertilized ovules, use of ⁶⁰Co-irradiated pollen, in vivo haploid inducers and wide hybridization are presented, suggesting that these methodologies could be implemented in tomato breeding programs to obtain doubled haploids.

Synthetic varieties (SVs) are populations generated by randomly mating their parents. They are a good alternative for low-input farmers who grow onions, maize, and other allogamous crops since the seed produced by a SV does not change from one generation to the next. Although SV progenitors are commonly pure lines, in this case a synthetic (SynTC) whose parents are t three-way line crosses, a very common type of maize hybrid grown in Mexico, is studied. The aim was to develop a general and exact equation for the inbreeding coefficient of a SynTC SynTC because of its relationship with the mean of economically important traits. This objective arose due to the need for a more advanced study in terms of determining whether SynTC can be applied specifically and accurately for any number of parents (t), plants per parent (m) and inbreeding coefficient (IC) of the initial lines (FL). A formula for the IC of the SynTC was derived that, given any values of FL (0 ≤ FL ≤ 1) and t, is specific for any value of m, not just for “large” numbers associated with the context in which the Hardy-Weinberg law is stated. It was found that SynTC is very sensitive to changes in m when m is not greater than eight, after which it tends to stabilize very quickly. In summary, unlike previously derived formulas, SynTC is exact for any values of t, m and FL.