Banana breeding consists of obtaining diploid, triploid, and tetraploid intra- and interspecific hybrids by conventional breeding methods with the objective of aggregating characteristics of agronomic and commercial interest. Given the narrow genetic base of bananas, Embrapa’s Banana Genetic Breeding Program (BGBP) aims at crosses between improved diploids (ID) (ID × ID) and between improved diploids (ID) and commercial triploids (ID × CTP) and tetraploids (ID × CTT), in order to increase the genetic base and variability in bananas regarding agronomic traits of interest and resistance to main biotic and abiotic factors. These improved diploids are resistant to main fungal diseases such as yellow (YSD) and black Sigatoka (BSD) disease and Fusarium wilt (race 1 and subtropical race 4), the latter being one of the most devastating diseases in bananas. The genetic diversity between 22 improved diploids and seven commercial banana triploids was analyzed using DNA molecular markers. Five IRAP (Inter-Retrotransposon Amplified Polymorphism, 7 ISSR (Inter-Simple Sequence Repeats) and 12 SSR (Simple Sequence Repeat) markers were used. The genetic dissimilarity matrix was based on the Jaccard dissimilarity index; clusters were separated using the UPGMA (Unweighted Pair Group Method With Arithmetic Mean) method and cophenetic correlation of 0.8755. This study of the genetic diversity between improved diploids and commercial triploids, based on the genetic dissimilarity matrix, revealed that the most dissimilar diploids were DM23 and DM15 (74%) and DM16 and DM15 (74%). The smallest genetic distances between the improved diploids and commercial triploids were between TCGN25 and DM17 (50%) and TCN26 and DM17 (50%). The genetic distance matrix also revealed important genotypes to be used in crosses in order to maintain good characteristics in commercial triploids when crossed with improved diploids. The results of our study provide better breeding strategies for one of the largest banana-breeding programs worldwide focused on the development of banana varieties resistant to main biotic and abiotic factors.

Senegalia bahiensis (Fabaceae family, Mimosoideae subfamily) is typical of an anthropic environment, and thus tolerates high levels of disturbance, which supports its use in restoration planting. However, widespread use and marketing of S. bahiensis seeds requires seed quality control, for which there is a dearth of protocols. The aim of the present study was to evaluate the influence of temperature and photoperiod on the germination of Senegalia bahiensis seeds from different matrix trees. Seeds were collected from fruits of 15 matrix trees in the municipality of Castro Alves, Bahia, Brazil. Two assays were performed, one for each parameter tested. The experimental design of both assays was completely randomized in a factorial design, and included three replicates of 25 seeds. The design of the first assay was 15 (matrix trees) × 3 (conditions - 25°C, 30°C and alternating temperatures between 25 and 30°C) and the design of the second assay was 14 (matrix trees) × 3 (conditions - 8 or 12 hours of light, or continuous light). The percentage of germination of normal seedlings, germination speed index, mean root length based on total seed number, shoot length, root length and total length were determined. The Tukey's test was used to compare mean values. The S. bahiensis matrix trees used in this study have different requirements in terms of temperature and photoperiod for seed germination. According to our findings, combining a temperature of 30°C and an 8 h period of light conveys the most suitable conditions to conduct germination tests for most matrix trees.

The fresh fruits of ‘Grande Naine’ (Cavendish AAA—Musa spp.) dominate the world market, especially in countries with a population in a situation of social vulnerability. However, Fusarium wilt, caused by the fungus Fusarium oxysporum f.sp. cubense race 4 Subtropical (Foc ST4), emerges as a serious threat to banana production, requiring the development of resistant cultivars based on biotechnological strategies, such as the induction of mutation in tissue culture. This study aimed to identify and characterize genetic variation in somaclones resistant to Fusarium oxysporum f.sp. cubense subtropical race 4 (Foc ST4), derived from ‘Grand Naine’ bananas, by molecular markers based on retrotransposons IRAP (Inter-retrotransposon Amplified Polymorphism) and REMAP (Retrotransposon-Microsatellite Amplified Polymorphism). Nine combinations of IRAP and six combinations of REMAP primers were used. The low number of polymorphic bands did not allow for genetic diversity studies; however, ten polymorphic bands between the somaclones and control were sequenced. Of these, three presented good base calling and were aligned, namely, 1AF, 2AF, and 3AF bands. Only the 1AF band presented function related to stress response with homology to a calcium-binding protein. These proteins act early in plant infection as secondary messengers activated by pathogen-associated molecular patterns (PAMPs), initiating the cascade of plant defense signals. The fact that this band is present in all somaclones reinforces previous assessments of their resistance to Foc ST4. The use of markers IRAP and REMAP produced polymorphic bands that can, through future primer design and field validations, accelerate the identification of resistant banana genotypes for use in banana genetic breeding programs.

The objective of this work was to evaluate the genetic diversity of Xanthomonas phaseoli p v. manihotis (Xpm) from eight populations from five cassava producing states in Brazil, through the rep-PCR (BOX-PCR and ERIC-PCR) and variable number of tandem repeat (VNTR) markers. Cassava leaves with symptoms of cassava bacterial blight were collected in eight municipalities, and the Xpm isolates were identified by amplification with primers specific for these isolates. The identity of the Xpm isolates was confirmed with the BOX-PCR, ERIC-PCR, and VNTR markers. The observed selection pressure, together with the mode of reproduction and the mechanisms that increase genetic variability, allows of the pathogen populations to adapt according to microclimate variation, contributing to a differentiated reproductive success. ERIC-PCR and VNTRs are the best markers for evaluating the genetic variability in the eight studied Xpm populations. However, ERIC-PCR is the marker that best separated the groups by population and presented a higher similarity between the isolates of the same population. The study of the genetic diversity of Xpm is key to improve disease monitoring and management strategies in cassava crops.

Ribossome-inactivating proteins (RIPs) are found in several plant, fungal, and bacterial species and play an important role in the plant defense system against phytopathogens. The present study aimed to characterize, in silico, the RIP gene and protein family in Jatropha curcas L. Genome annotation in the Jatropha curcas Database (JCDB) enabled the identification of a total of twelve RIP genes. The genes JcRIP1 to JcRIP11 encode curcin, a type I RIP found in physic nut, whereas JcRIP12 is a gene similar to those encoding ricin, a type II RIP present in Ricinus communis L. Light-responsive, MYB, and MYC cis-elements were identified in all promoter regions of the JcRIP genes. To a lesser extent, cis-elements responsive to biotic and abiotic stresses and phytohormones were also detected. JcRIP3 showed the highest expression among the analyzed tissues. In addition to seeds and leaves, RIP gene expression was also observed in stems, roots, and flowers. The number of amino acid residues of physic nut RIP proteins ranged from 291 (JcRIP8) to 551 (JcRIP12). Eight of the twelve JcRIPs exhibited a well-conserved EAAR motif (Glu185-Ala186-Ala187-Arg188). The YFF motif (Tyr99-Phe100-Phe101) was conserved in all JcRIPs analyzed in this study. The results of this work provide knowledge about conditions and locations of JcRIP gene expression, as well as the characteristics of corresponding proteins. This work can contribute to future genetic improvement studies focused on biotic stress, molecular docking analyses aimed at reducing/inhibiting harmfulness, and in vitro tests against phytopathogens.