Sexual dimorphism and the effect of wild introgressions on recombination in cassava (Manihot esculenta Crantz) breeding germplasm

Recombination has essential functions in meiosis, evolution, and breeding. The frequency and distribution of crossovers dictate the generation of new allele combinations and can vary across species and between sexes. Here, we examine recombination landscapes across the 18 chromosomes of cassava (Manihot esculenta Crantz) with respect to male and female meioses and known introgressions from the wild relative Manihot glaziovii. We used SHAPEIT2 and duoHMM to infer crossovers from genotyping-by-sequencing (GBS) data and a validated multi-generational pedigree from the International Institute of Tropical Agriculture (IITA) cassava breeding germplasm consisting of 7,020 informative meioses. We then constructed new genetic maps and compared them to an existing map previously constructed by the International Cassava Genetic Map Consortium (ICGMC). We observed higher recombination rates in females compared to males, and lower recombination rates in M. glaziovii introgression segments on chromosomes 1 and 4, with suppressed recombination along the entire length of the chromosome in the case of the chromosome 4 introgression. Finally, we discuss hypothesized mechanisms underlying our observations of heterochiasmy and crossover suppression and discuss the broader implications for plant breeding.

Production of bioethanol from wild cassava crude starch (Manihot glaziovii Muell. Arg) using different microbial types and fermentation times

Wild cassava (Manihot glaziovii Muell. Arg) is one of the varieties of cassava that contains toxic compounds cyanogenic glucosides, which cause unmarketable food products more suitable to be processed into bioethanol. This wild cassava plant produces tubers four times in weight compared to that of ordinary cassava, and the flesh contains about 40–70% starch by dry weight. This study aimed to determine the effect of the microbial types and fermentation times on bioethanol production from M. glaziovii Muell. Arg crude starch and to determine the type of microbes and fermentation time that can produce the highest bioethanol product from M. glaziovii Muell. Arg crude starch. This study consists of two factors using a factorial randomized block design (RBD). The first factor was the type of microbe which consists of 2 different microbes, namely R5I3 isolates and Saccharomyces cerevisiae ATCC 9763. The second factor was the fermentation time which consists of 4 levels, namely 3, 4, 5 and 6 days. The observed parameters were total dissolved solids value, pH value, reducing sugar content, and ethanol content. The data obtained were analyzed using analysis of variance (ANOVA) and continued with Tukey’s HSD post hoc tests. The results showed that fermentation using R5I3 isolates with a fermentation time of 5 days was the best treatment to obtain a maximum ethanol of 21.64±3.03 g/L, with a final pH value of 4.70±0.14, total dissolved solids 4.10±0.14°Brix and reducing sugar content of 0.91±0.02 g/L. Therefore, the new isolate R513 was highly potential for producing bioethanol from wild cassava crude starch.

Sexual dimorphism and the effect of wild introgressions on recombination in cassava (Manihot esculenta Crantz) breeding germplasm

Recombination has essential functions in meiosis, evolution, and breeding. The frequency and distribution of crossovers dictate the generation of new allele combinations and can vary across species and between sexes. Here, we examine recombination landscapes across the 18 chromosomes of cassava (Manihot esculenta Crantz) with respect to male and female meioses and known introgressions from the wild relative Manihot glaziovii. We used SHAPEIT2 and duoHMM to infer crossovers from genotyping-by-sequencing (GBS) data and a validated multi-generational pedigree from the International Institute of Tropical Agriculture (IITA) cassava breeding germplasm consisting of 7,020 informative meioses. We then constructed new genetic maps and compared them to an existing map previously constructed by the International Cassava Genetic Map Consortium (ICGMC). We observed higher recombination rates in females compared to males, and lower recombination rates in M. glaziovii introgression segments on chromosomes 1 and 4, with suppressed recombination along the entire length of the chromosome in the case of the chromosome 4 introgression. Finally, we discuss hypothesized mechanisms underlying our observations of heterochiasmy and crossover suppression and discuss the broader implications for plant breeding.

Reaction kinetics of lactic acid fermentation from bitter cassava (Manihot glaziovii) starch by Lactobacillus casei

One of the utilizations of bitter cassava is modified cassava flour (Mocaf) production using the fermentation process by Lactobacillus casei. The Mocaf has potential as the future of food security products. It has a characteristic property similar to wheat flour. Lactic acid was also produced as a by‐product during fermentation. After 40 h of fermentation, the proximate composition content of Mocaf was lactic acid content of 0.000928 g/L, hydrogen cyanide levels of 0.02 ppm, starch content of 59.13%, amylose content of 12.98% and amylopectin content of 46.15%. In the scaling‐up process from a laboratory scale to a pilot and industrial scale, modeling is needed. There are five equation models used to describe the kinetic reactions of lactic acid from bitter cassava starch: Monod, Moser, Powell, Blackman, and Product Inhibitor. Each parameter was being searched by a fitting curve using sigmaplot 12.0. The best result in terms of the highest R2 (0.65913) was obtained in the Powell equation with the value of µmax of 1.668/h, Ks of 123.4 g/L, and maintenance rate (m) of 4.672. The kinetic data obtained can be used to design biochemical reactors for industrial scale Mocaf flour production.

Production of biodiesel by enzymatic catalysis from the castor oil: an analytical chemical study

The study aimed at the development of a method for obtaining biodiesel by transesterification by via methylic from castor oil using biocatalysts. Seven varieties of lipase (PPL, Candida rugosa, OS cepacea, OS cepacea immobilized on diatomaceous earth, Novozyme 435, Lipozyme and Lipozyme RM) and seven enzymatic sources from a vegetable origin (latex of the species Ficus benjamina, Manihot glaziovii Muell. Arg., Calotropis procera, Jatropha curcas L., Ficus pumila, Euphorbia tirucalli L.) were tested. Enzymatic sources of plant origin were submitted, initially, the hydrolytic activity tests to evaluate their potential as biocatalysts and, from the results obtained, two samples were selected for the experiments further synthesis of biodiesel. Validation of the method of production of biodiesel evaluated linearity, reproducibility (precision), recovery (accuracy) and the limits of detection and quantification. Among the sources of enzymes used in the synthesis of biodiesel presented the best result was the commercial enzyme Novozym 435 with 55.33% conversion yield of biodiesel in initial tests. Were conducted new tests for optimization of reactional parameters co-solvent, alcohol: oil ratio, amount of enzyme and solvent for recovery of the enzyme, which enabled a maximum yield of biodiesel to 98.84%.

Historical Introgressions from a Wild Relative of Modern Cassava Improved Important Traits and May Be Under Balancing Selection

Introgression of alleles from wild relatives has often been adaptive in plant breeding. However, the significance of historical hybridization events in modern breeding is often not clear. Cassava (Manihot esculenta) is among the most important staple foods in the world, sustaining hundreds of millions of people in the tropics, especially in sub-Saharan Africa. Widespread genotyping makes cassava a model for clonally propagated root and tuber crops in the developing world, and provides an opportunity to study the modern benefits and consequences of historical introgression. We detected large introgressed Manihot glaziovii genome-segments in a collection of 2742 modern cassava landraces and elite germplasm, the legacy of a 1930s era breeding to combat disease epidemics. African landraces and improved varieties were, on average, 3.8% (max 13.6%) introgressed. Introgressions accounted for a significant (mean 20%, max 56%) portion of the heritability of tested traits. M. glaziovii alleles on the distal 10 Mb of chr. 1 increased dry matter and root number. On chr. 4, introgressions in a 20 Mb region improved harvest index and brown streak disease tolerance. We observed the introgression frequency on chr. 1 double over three cycles of selection, and that later stage trials selectively excluded homozygotes from consideration as varieties. This indicates a heterozygous advantage of introgressions. However, we also found that maintaining large recombination-suppressed introgressions in the heterozygous state allowed the accumulation of deleterious mutations. We conclude that targeted recombination of introgressions would increase the efficiency of cassava breeding by allowing simultaneous fixation of beneficial alleles and purging of genetic load.

Sexual dimorphism and the effect of wild introgressions on recombination in Manihot esculenta

ABSTRACTRecombination has essential functions in evolution, meiosis, and breeding. Here, we use the multi-generational pedigree, consisting of 7,165 informative meioses (3,679 female; 3,486 male), and genotyping-by-sequencing (GBS) data from the International Institute of Tropical Agriculture (IITA) to study recombination in cassava (Manihot esculenta). We detected recombination events using SHAPEIT2 and duoHMM, examined the recombination landscape across the 18 chromosomes of cassava and in regions with known introgressed segments from cassava’s wild relative Manihot glaziovii, constructed a genetic map and compared it to an existing map constructed by the International Cassava Genetic Map Consortium (ICGMC), and inspected patterns of recombination placement in male and female meioses to see if there is evidence of sexual dimorphism in crossover distribution and frequency. We found that the placement of crossovers along chromosomes did not vary between the two sexes but that females undergo more meiotic recombination than males. We also observed that introgressions from M. glaziovii decreased recombination in the introgressed region and, in the case of chromosome 4, along the entire length of the chromosome that the introgression is on. We observed a dosage effect on chromosome 1, possibly suggesting the presence of a variant on the M. glaziovii haplotype that leads to lower overall recombination in the introgressed region.