Transposable Element Expression and Regulation Profile in Gonads of Interspecific Hybrids of Drosophila arizonae and Drosophila mojavensis wrigleyi

Interspecific hybridization may lead to sterility and/or inviability through differential expression of genes and transposable elements (TEs). In Drosophila, studies have reported massive TE mobilization in hybrids from interspecific crosses of species presenting high divergence times. However, few studies have examined the consequences of TE mobilization upon hybridization in recently diverged species, such as Drosophila arizonae and D. mojavensis. We have sequenced transcriptomes of D. arizonae and the subspecies D. m. wrigleyi and their reciprocal hybrids, as well as piRNAs, to analyze the impact of genomic stress on TE regulation. Our results revealed that the differential expression in both gonadal tissues of parental species was similar. Globally, ovaries and testes showed few deregulated TEs compared with both parental lines. Analyses of small RNA data showed that in ovaries, the TE upregulation is likely due to divergence of copies inherited from parental genomes and lack of piRNAs mapping to them. Nevertheless, in testes, the divergent expression of genes associated with chromatin state and piRNA pathway potentially indicates that TE differential expression is related to the divergence of regulatory genes that play a role in modulating transcriptional and post-transcriptional mechanisms.

Ovarian Incompatibility in Tuberose (Polianthes Tuberosa L.) Cultivars and Breeding Lines

Background: Incompatibility occurs frequently in the plant system upon intra- or interspecific crosses resulting in several pollination barriers. The modest understanding on the breeding behaviour and mechanisms governing tuberose (Polianthes tuberosa L.) through this study will direct us to appraise the pollination and post pollination events on self- and cross- incompatibility and seed set behaviour for cross breeding programme.Results: Self-pollination of tuberose cultivars Arka Prajwal, Mexican Single and Arka Sugandhi failed to produce pods upon autogamy and geitonogamy. Pollen-pistil interaction study of incompatible cultivar Arka Prajwal substantiates that pollen tube enters the ovule within 24 hours after pollination. It discharges its contents into the embryo on the 1st day after pollination and polysaccharide granules evident upon fluorescence microscopic study. The pollen tube growth rates of self and controlled pollination were similar; however, sterility was expressed in the ovary. The female gametophytic development in self and cross incompatible cultivar Arka Prajwal showed normal development initially after pollination whereas embryosac degeneration was observed at later stage. Complete degeneration of the integument and nucellar cells was also observed. Conclusions: This study is the first to elucidate the occurrence of pseudo self-incompatibility in tuberose by identifying tuberose cultivars and breeding lines which produce pods upon geitonogamy. A positive pollen-pistil interaction with the degeneration of embryosac, integument and nucellar cell and pod shrinkage, abortion and fall confirms the prevalence of the ‘Ovarian Incompatibility’ or ‘Late-Acting Incompatibility’ in tuberose.

Albinism in F1 Hybrids Hinders Geneflow Between Cultivated Chickpea (Cicer arietinum L.) and the Tertiary Gene Pool Species, Cicer Pinnatifidum

Wild Cicer species, especially those in the tertiary gene pool, carry useful alleles for chickpea improvement. The aim of this study was to evaluate the crossability and geneflow between three chickpea cultivars (as female parents) and four cross-incompatible Cicer pinnatifidum accessions (as pollen parents) from the tertiary gene pool. Ten crosses were conducted. One fully developed healthy F1 seed was harvested in vivo from the ICC 4958 × ICC 17269 cross, but the seedling developed an albino phenotype at 4–5 days after germination. Unlike other crosses, those involving the cultivar ICCV 96030 generated a large number of pods with comparatively large ovules. One albino plantlet was obtained from the ICCV 96030 × ICC 17269 cross by embryo rescue. Crosses involving ICCV 10 resulted in flower drop and poor pod set. These variable genotype-specific responses of pod, ovule, and seed development indicate that genetic factors affect the formation of interspecific hybrids. Although pod and seed formation in these interspecific crosses can be improved, geneflow between these materials is hindered by a strong genetic factor conferring albinism in the F1 hybrids.

Identification of QTL Combinations that Cause Spikelet Sterility in Rice Derived from Interspecific Crosses

Background The exploitation of useful genes through interspecific and intersubspecific crosses has been an important strategy for the genetic improvement of rice. Postzygotic reproductive isolation routinely occurs to hinder the growth of pollen or embryo sacs during the reproductive development of the wide crosses. Result In this study, we investigated the genetic relationship between the hybrid breakdown of the population and transferred resistance genes derived from wide crosses using a near-isogenic population composed of 225 lines. Five loci (qSS12, qSS8, qSS11, ePS6-1, and ePS6-2) associated with spikelet fertility (SF) were identified by QTL and epistatic analysis, and two out of five epistasis interactions were found between the three QTLs (qSS12, qSS8 and qSS11) and background marker loci (ePS6-1 and ePS6-2) on chromosome 6. The results of the QTL combinations suggested a genetic model that explains most of the interactions between spikelet fertility and the detected loci with positive or negative effects. Moreover, the major-effect QTLs, qSS12 and qSS8, which exhibited additive gene effects, were narrowed down to 82- and 200-kb regions on chromosomes 12 and 8, respectively. Of the 13 ORFs present in the target regions, Os12g0589400 and Os12g0589898 for qSS12 and OS8g0298700 for qSS8 induced significantly different expression levels of the candidate genes in rice at the young panicle stage. Conclusion The results will be useful for obtaining a further understanding of the mechanism causing the hybrid breakdown of a wide cross and will provide new information for developing rice cultivars with wide compatibility.

Interacting host modifier systems control Wolbachia-induced cytoplasmic incompatibility in a haplodiploid mite

Many reproductive parasites such as Wolbachia spread within host populations by inducing cytoplasmic incompatibility (CI). CI occurs when parasite-modified sperm fertilizes uninfected eggs. In haplodiploid hosts, CI can lead to different phenotypes depending on whether the fertilized eggs die or develop into males. Genetic conflict theories predict the evolution of host modulation of CI, which in turn strongly influences the stability of reproductive parasitism. Yet, despite the ubiquity of CI-inducing parasites in nature, there is no conclusive evidence for strong intraspecific host modulation of CI strength and phenotype. Here, we tested for intraspecific host modulation of Wolbachia-induced CI in haplodiploid Tetranychus spider mites. Using a single CI-inducing Wolbachia variant and mitochondrion, a Tetranychus urticae nuclear panel was created that consisted of infected and cured near-isogenic lines. We performed a highly replicated age-synchronized full diallel cross comprised of incompatible and compatible control crosses. We uncovered host modifier systems that strongly suppress CI strength when carried by infected T. urticae males. Interspecific crosses showed that the male modifier systems suppress CI strength across species boundaries. We also observed a continuum of CI phenotypes in our crosses and identified strong intraspecific female modulation of CI phenotype when paired with a specific male genotype. Crosses established a recessive genetic basis for the maternal effect and were consistent with polygenic Mendelian inheritance. Our findings identify spermatogenesis as an important target of selection for host suppression of CI strength and underscore the importance of maternal genetic effects for the CI phenotype. Both mechanisms interacted with the genotype of the mating partner, revealing that intraspecific host modulation of CI strength and phenotype is underpinned by complex genetic architectures.

Genetic Analysis of Various Traits in Oilseed Brassicas

Background: The combining ability and manifestation of heterosis within and among the species of oilseed brassicas (B. campestris, B. napus and B. juncea) were studied for yield and yield related traits in 12F1 combinations. Methods: All crosses (12F1) along with their parents (7 parents) were sown in randomized complete block design (RCBD) with three replications. Result: The analysis of variance showed extensive variability among the genotypes. The physical appearance of interspecific crosses was intermediate. B. campestris showed significant GCA effects among lines and B. juncea among testers for seed yield per plant. General combining behaviour of B. campestris was better as compared to B. napus and B. juncea. The SCA effects were higher within species than among the species. This also revealed that within the species B. juncea had more SCA (17.45) than B. napus (9.82) and B. campestris (8.01) for seed yield. The SCA showed the improvement of B. Juncea, is the best than other two species. It is also concluded that to obtain better yield, crossing within the species is more appropriate than among the species. Moreover, to introduce novel traits in brassica species is possible through interspecific hybridization.

De novo super-early progeny in interspecific crosses Pisum sativum L. × P. fulvum Sibth. et Sm

Earliness in crop plants has a crucial role in avoiding the stress of drought and heat, which are the most important challenging stressors in crop production and are predicted to increase in the near future due to global warming. Furthermore, it provides a guarantee of vegetable production in the short growing season of agricultural lands in the northern hemisphere and at high altitudes. The growing human population needs super early plant cultivars for these agricultural lands to meet future global demands. This study examined de novo super-early progeny, referred to as much earlier than that of the earlier parent, which flowered in 13–17 days and pod setting in 18–29 days after germination, discovered in F2 and studied up to F5 derived from interspecific crosses between garden pea (P. sativum L.) and the most distant relative of pea (P. fulvum Sibth. et Sm.). De novo super-early progeny were found to be earlier by about one month than P. sativum and two months than P. fulvum under short day conditions in the F5 population. In respect of days to flowering and pod setting, de novo super-early progeny had a relatively high level of narrow sense heritability (h2 = 82% and 80%, respectively), indicating that the selections for earliness in segregating populations was effective for improvement of extreme early maturing varieties. De novo super-early progeny could be grown under heat stress conditions due to the escape ability. Vegetable types were not only high yielding but also free of any known undesirable traits from the wild species, such as pod dehiscence and non-uniform maturity. It could be considered complementary to “speed breeding”, possibly obtaining more than six generations per year in a suitable climate chamber. Not only de novo super-early progeny but also transgressive segregation for agro-morphological traits can be created via interspecific crosses between P. sativum and P. fulvum, a precious unopened treasure in the second gene pool. Useful progeny obtained from crossing wild species with cultivated species reveal the importance of wild species.

Contribution of Wild Relatives to Durum Wheat (Triticum turgidum subsp. durum) Yield Stability across Contrasted Environments

Durum wheat (Triticum turgidum subsp. durum) is mostly grown in Mediterranean type environments, characterized by unpredictable rainfall amounts and distribution, heat stress, and prevalence of major diseases and pests, all to be exacerbated with climate change. Pre-breeding efforts transgressing adaptive genes from wild relatives need to be strengthened to overcome these abiotic and biotic challenges. In this study, we evaluated the yield stability of 67 lines issued from interspecific crosses of Cham5 and Haurani with Triticum dicoccoides, T. agilopoides, T. urartu, and Aegilops speltoides, grown under 15 contrasting rainfed and irrigated environments in Morocco, and heat-prone conditions in Sudan. Yield stability was assessed using parametric (univariate (e.g., Bi, S2di, Pi etc) and multivariate (ASV, SIPC)) and non-parametric (Si1, Si2, Si3 and Si6) approaches. The combined analysis of variance showed the highly significant effects of genotypes, environments, and genotype-by-environment interaction (GEI). The environments varied in yield (1370–6468 kg/ha), heritability (0.08–0.9), and in their contribution to the GEI. Several lines derived from the four wild parents combined productivity and stability, making them suitable for unpredictable climatic conditions. A significant advantage in yield and stability was observed in Haurani derivatives compared to their recurrent parent. Furthermore, no yield penalty was observed in many of Cham5 derivatives; they had improved yield under unfavorable environments while maintaining the high yield potential from the recurrent parent (e.g., 142,026 and 142,074). It was found that a limited number of backcrosses can produce high yielding/stable germplasm while increasing diversity in a breeding pipeline. Comparing different stability approaches showed that some of them can be used interchangeably; others can be complementary to combine broad adaption with higher yield.

Evaluation of a Set of Hordeum vulgare subsp. spontaneum Accessions for β-Glucans and Microelement Contents

Barley is one of the oldest domesticated crops in the world and is mainly used for feed and malt and to a lesser extent as food. The use of barley as food is a tradition in communities in some countries of North Africa, Europe, and Asia. However, due to the health-promoting properties of barley grain, there is an increasing interest in such use. The International Center for Agricultural Research in the Dry Areas (ICARDA) has a global mandate for barley improvement and holds rich in-trust collections of cultivated and wild Hordeum species. The present study aims to evaluate 117 accessions of Hordeum spontaneum for their contents of β-glucan and microelements for breeding new varieties with enhanced nutritional value. The bulked seed accessions of Hordeum spontaneum were grown over two seasons, and the single plant derived seeds from these accessions were compared to 36 elite lines and varieties of cultivated barley in the second season in Morocco. The results showed large differences in β-glucan and microelements in both the bulk and the single plant seed accessions. The contents of β-glucans ranged from 1.44 to 11.3% in the Hordeum spontaneum accessions and from 1.62 to 7.81% in the cultivated barley lines. Large variations were found for the microelements content, but no differences were noticed between the wild and the cultivated species. However, some accessions of Hordeum spontaneum had higher combined contents of Iron, Zinc, and Selenium. Such accessions are used in interspecific crosses to develop biofortified barley germplasm and varieties.

Phenotype and genotype variability of interspecific rice lines related to bacterial leaf blight resistance (Xanthomonas oryzae pv. oryzae) character

Yuriyah S, Darnaedi D, Setia TM, Windarsih G, Utami DW. 2021. Phenotype and genotype variability of interspecific rice lines related to bacterial leaf blight resistance (Xanthomonas oryzae pv. oryzae) character. Biodiversitas 22: 4123-4130. Wild rice species are the source of the gene pool for rice genetic diversity. The cross-species crosses (interspecific crosses) play an important role in breeding, namely in terms of expanding the diversity of desirable characters, such as disease resistance and improvement in yield potential. Currently, the genes from wild rice species have been successfully introgressed into cultivated rice so that they can overcome the rice production constraints, including the introgression of genes for the bacterial leaf blight (BLB) resistance. The purpose of this study was to analyze the variability of phenotype and genotype performance of lines derived from wild rice species for the character of resistance to BLB disease. A total of 33 selected backcross lines derived from wild rice species of O. rufipogon and O. glaberrima as the donor parents and 2 control varieties (resistant and susceptible to BLB disease), were used in this study. The evaluation of phenotype and genotype of resistance characters to BLB disease was carried out during a vegetative phase of the plant. The resistance evaluation was carried out in a greenhouse, while the genotype performance was analyzed using 4 STS markers linked to Xa4, Xa7, and Xa13 genes. The result of the phenotype evaluation showed that there were variations among the resistance of the tested lines. Three lines derived from a Situ Bagendit/Oryza rufipogon cross were resistant to all BLB races used in the testing. Those three lines indicated to have the allele of the Xa7 resistance gene based on the genotype performance which grouped with the Code variety that had the Xa7 resistance gene.