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Although resistance to diseases is genetically controlled, the environment has a strong influence on the reaction of plants to pathogens. Thus, the selection of superior genotypes in plant breeding programs can be more efficient the more intrinsically the environmental factors that influence the trait of interest are considered. This study aimed to investigate the adaptive genetic capacity of popcorn maize plants in relation to the occurrence of southern corn leaf blight (SCLB) in contrasting environments regarding nitrogen availability. Gene effects were estimated based on the implementation of a full diallel without reciprocals from which 28 hybrids were obtained. These hybrids, together with their parents, were evaluated in four environments in relation to SCLB reaction. The studied characteristics were area under the disease progress curve, estimated for severity and incidence. The experimental design was a 6 × 6 square lattice with three replications. Significant effects were found on the interactions between genotype, general combining ability, and specific combining ability × environment, demonstrating severe implications of soil nitrogen concentration on the performance of parent lines and hybrids. Dominant gene effects prevailed in the expression of resistance to SCLB. Considering the need for an environmentally and economically sustainable awareness in the control of this disease, it is of interest to take advantage of the heterotic effect contained in the combination L77 × P7, which stood out in relation to the other hybrids for the evaluated environments.

We have investigated the molecular structure and two-photon absorption (2PA) properties relationship of two push–pull poly(fluorene) derivatives containing benzoselenadiazole and benzothiadiazole units. For that, we have used the femtosecond wavelength-tunable Z-scan technique with a low repetition rate (1 kHz) and an energy per pulse on the order of nJ. Our results show that both 2PA spectra present a strong 2PA (around 600 GM (1 GM = 1 × 10−50 cm4·s·photon−1)) band at around 720 nm (transition energy 3.45 eV) ascribed to the strongly 2PA-allowed 1Ag-like → mAg-like transition, characteristic of poly(fluorene) derivatives. Another 2PA band related to the intramolecular charge transfer was also observed at around 900 nm (transition energy 2.75 eV). In both 2PA bands, we found higher 2PA cross-section values for the poly(fluorene) containing benzothiadiazole unit. This outcome was explained through the higher charge redistribution at the excited state caused by the benzothiadiazole group as compared to the benzoselenadiazole and confirmed by means of solvatochromic Stokes shift measurements. To shed more light on these results, we employed the sum-over-states approach within the two-energy level model to estimate the maximum permanent dipole moment change related to the intramolecular charge transfer transition.

Agricultural expansion and the need for sustainable cultivation are challenges faced by researchers involved in the generation of new cultivars that can adapt to abiotic stress. Knowledge of the genetic effects of characteristics related to efficiency and responsiveness to phosphorus use must be considered when implementing methods to obtain better genotypes. The aim of this study was to characterize and select popcorn hybrids based on their efficiency and responsiveness to phosphorus use, and estimate their combining abilities and genetic effects via diallel analysis to implement improvement programs for sustainable agriculture. Eight contrasting inbred lines were used to obtain simple hybrids for diallel analysis. Twenty-eight diallelic hybrids plus the popcorn parental lines were evaluated at two different sites under two contrasting environments for soil phosphorus availability (6 × 6 lattice design). Grain yield, popping expansion, and volume of expanded popcorn per hectare were measured. A combined analysis of variance and a test of means were performed. The classification and utilization of the phosphorus use efficiency index, according to the grain yield performance of the hybrids under contrasting environments, was considered. Through model 2 of the Griffing's diallel analysis method, the general and specific combining abilities were estimated, along with their environmental interactions. The best strategy to obtain genotypes that are efficient and responsive to phosphorus involves exploring popcorn hybrids using genitors that result in the accumulation of additive genes that promote popping expansion. Hybrids P7 × L80, P7 × L59, P7 × L76, and P6 × L80 presented promising results and may be evaluated as cultivation options in phosphorus-deficient soils.

Increasing the efficiency in selecting and recommending superior genotypes for black spot resistance in papaya requires proper field evaluation. A randomized block design with six genotypes and four replications was used to evaluate the coefficient of repeatability (r) and the minimum number of measurements. For this, the leaf with early symptoms of black spot (LES), the leaf with incidence of black spot (IBS), and the severity of black spot estimated on fifth leaf (SBS5L) and leaf with axil attached to first open flower (SBSOF) were quantified monthly for nine months. Subsequently, the coefficient of repeatability (r) and the minimum number of measurements (η) were estimated using four distinct methods: ANOVA, PCMCov, PCMCor, and SAMCor. The results suggest that traits IBS and SBSOF have high repeatability, thus requiring fewer measurements (five and three measurements, respectively for IBS and SBSOF) to select black spot resistant papaya genotypes.

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. Funding was also provided by FAPERJ, with the project E26/201.813/2017 to SK and E26/202.761/2017 to AA. Funding to JR by Fundação para a Ciência e a Tecnologia (FCT), Portugal, through the research units UID/UIDB/00239/2020 (CEF), and UIDP/04035/2020 (GeoBioTec) is also greatly acknowledged. JA acknowledges the support of Catalan Institution for Research and Advanced Studies (ICREA, Generalitat de Catalunya, Spain), through the ICREA Academia Program.

This article reports on a comprehensive study of the two-photon absorption (2PA) properties of six novel push-pull octupolar triarylamine compounds as a function of the nature of the electron-withdrawing groups. These compounds present an octupolar structure consisting of a triarylamine core bearing two 3,3′-bis(trifluoromethyl)phenyl arms and a third group with varying electron-withdrawing strength (H < CN < CHO < NO2 < Cyet < Vin). The 2PA cross-sections, measured by using the femtosecond open-aperture Z-scan technique, showed significant enhancement from 45 up to 125 GM for the lowest energy band and from 95 up to 270 GM for the highest energy band. The results were elucidated based on the large changes in the transition and permanent dipole moments and in terms of (i) EWG strength, (ii) degree of donor-acceptor charge transfer and (iii) electronic coupling between the arms. The 2PA results were eventually supported and confronted with theoretical DFT calculations of the two-photon transition oscillator strengths.

In the current study, the morphological traits in 222 individuals of the UCP-C0 base population were evaluated to distinguish the phenotypic variability and thus to be used in the papaya recurrent selection program. The studied traits showed considerable differences among the individuals. The fruit weight ranged from 279.7 to 1808.0 g with average of 859.7 g, the number of commercial fruits ranged from 5 to 125 fruits, the fruit and pulp firmness ranged from 76.69 and 59.44 N to 166.70 and 132.93 N respectively, while the soluble solids content was between 5.10 and 14.93° Brix. The principal component analysis showed that five components explained 76% of the total variance. Morphological cluster analysis based on the UPGMA method showed 13 distinct clusters among all the studied accessions, and the fruit weight was that most contributed for the genetic diversity. The results show that the UCP-C0 has wide genetic variability and therefore the choice of genotypes used as parents in the generation of the UCP-C0 was very effective to generate a broad base population for most of the agronomic and fruit quality traits. The strategy to use the highly heterogeneous and heterozygous dioic progenies, and the pollen mix of elite genitors, contributed to the observed results, mainly by the genetic variability present in them. A broad base population is fundamental to establish the recurrent selection program, a classical methodology that may provide superior genotypes at short and long terms.

Papaya has a narrow genetic base concerning disease resistance, with few genetically distinct cultivars for planting in the world. Losses in crop production caused by fungal and viral diseases, added to the absence of resistant cultivars available to producers, have reduced the competitiveness of crops. Therefore, this study aimed to select promising individuals for resistance to phoma spot and black spot based on direct or combined genetic gains in the base population of the recurrent papaya selection. The population used in this study originated from the crossing of dioecious, female individuals and holders of a gene pool for resistance to phoma spot and black spot. These were crossed with elite individuals with a gene pool for production traits and fruit quality. The experiment was carried out without an experimental design, containing one plant per plot. Three measurements were taken on 255 individuals for five traits of disease resistance, being: four associated with black spot (incidence and severity on the leaf and fruit) and one associated with phoma spot (severity on the leaf). With the observations obtained, the REML/BLUP procedure was performed to estimate the temporary and permanent environmental effects. Such values were used to know the genetic parameters of the population and to elaborate a combined selection index, as well as to compare the gains with the direct selection. The results indicate environmental variance was relatively high witch low repeatability for the traits. Both selection strategies provide gains in reducing the diseases studied. Combined selection is recommended as it provides greater expected gain than direct selection. However, direct selection can be considered for the development of lines per se, as it offers the opportunity to already select superior individuals during the process of breeding the recurrent population or, to be part of the recombination phase.

Nitrogen (N) availability plays a crucial role in plant development. However, studies indicate that the pathosystem of pathogenic fungi, such as Bipolaris maydis, which causes Southern Corn Leaf Blight (SCLB) in popcorn, interacts with N availability. Therefore, this study seeks to select popcorn inbred lines (ILs), considering contrasting environments regarding N availability (low N—LN and optimal N—ON). For this, 90 ILs from 16 populations from tropical and temperate climates from South America were evaluated in five experiments using a randomized complete block design (three replications), with four common controls. From the tests, the level of severity of the ILs to SCLB was evaluated. Three trials showed greater severity in ON, one trial had higher severity in LN, and one trial did not show significant differences. However, the genotype x nitrogen level (GxN) interaction was always present. Of the 90 ILs, 73 showed resistance in both N levels, three only in LN, and four only in ON, while 10 were susceptible in both environments. On average, the lines were more susceptible in ON, and the observed GxN interactions indicate that there is a distinct behavior of the genotypes regarding the response to N in the soil, which reinforces the importance of selection in contrasting environments.

Black spot (Asperisporium caricae) is one of the main foliar fungal diseases of papaya crops. This disease acts directly on leaves and fruits causing leaf area reduction and fruit deterioration. The quantification of diseases is a fundamental part of the disease management and control process; therefore, a scale is required to help quantify black spot disease. The objective of this work was to propose a standardized methodology to quantify black spot severity in papaya leaves. A scale was developed considering the maximum and minimum values of the disease in the field that included eight levels of severity: 0.1, 0.3, 0.6, 1.0, 2.3, 5.0, 10.0, and 20.0%. Without the aid of a scale the disease is often overestimated, with absolute errors of approximately 75%. When the scale was used, 100% of the evaluators showed improved accuracy and precision, and absolute error was reduced to the 10% range. The scale also provided good repeatability and high reproducibility. The use of the scale provided an improvement in the R2 values, with mean values of 93 and 92 in the second and third evaluations, respectively, demonstrating that the scale is useful for different aspects of the pathosystem of A. caricae, such as for determining the efficiency of fungicides, characterization of varietal resistance, construction of the disease progression curve, and estimation of damage.