Core binding factor subunit β plays diverse and essential roles in the male germline

Much of the foundation for lifelong spermatogenesis is established prior to puberty, and disruptions during this developmental window negatively impact fertility long into adulthood. However, the factors that coordinate prepubertal germline development are incompletely understood. Here, we report that core-binding factor subunit-β (CBFβ) plays critical roles in prepubertal development and the onset of spermatogenesis. Using a mouse conditional knockout (cKO) approach, inactivation of Cbfb in the male germline resulted in rapid degeneration of the germline during the onset of spermatogenesis, impaired overall sperm production, and adult infertility. Utilizing a different Cre driver to generate another Cbfb cKO model, we determined that the function of CBFβ in the male germline is likely limited to undifferentiated spermatogonia despite expression in other germ cell types. Within undifferentiated spermatogonia, CBFβ regulates proliferation, survival, and overall maintenance of the undifferentiated spermatogonia population. Paradoxically, we discovered that CBFβ also distally regulates meiotic progression and spermatid formation but only with Cbfb cKO within undifferentiated spermatogonia. Spatial transcriptomics revealed that CBFβ modulates cell cycle checkpoint control genes associated with both proliferation and meiosis. Taken together, our findings demonstrate that core programs established within the prepubertal undifferentiated spermatogonia population are necessary for both germline maintenance and sperm production

Identification of quantitative trait loci under drought conditions in tropical maize. 2. Yield components and marker-assisted selection strategies

In most maize-growing areas yield reductions due to drought have been observed. Drought at flowering time is, in some cases, the most damaging. In the experiment reported here, trials with F3 families, derived from a segregating F2 population, were conducted in the field under well-watered conditions (WW) and two other water-stress regimes affecting flowering (intermediate stress, IS, and severe stress, SS). Several yield components were measured on equal numbers of plants per family: grain yield (GY), ear number (ENO), kernel number (KNO), and 100-kernel weight (HKWT). Correlation analysis of these traits showed that they were not independent of each other. Drought resulted in a 60% decrease of GY under SS conditions. By comparing yield under WW and SS conditions, the families that performed best under WW conditions were found to be proportionately more affected by stress, and the yield reductions due to SS conditions were inversely proportional to the performance under drought. Moreover, no positive correlation was observed between a drought-tolerance index (DTI) and yield under WW conditions. The correlation between GY under WW and SS conditions was 0.31. Therefore, in this experiment, selection for yield improvement under WW conditions only, would not be very effective for yield improvement under drought. Quantitative trait loci (QTLs) were identified for GY, ENO and KNO using composite interval mapping (CIM). No major QTLs, expressing more then 13% of the phenotypic variance, were detected for any of these traits, and there were inconsistencies in their genomic positions across water regimes. The use of CIM allowed the evaluation of QTL-by-environment interactions (Q×E) and could thus identify “stable” QTLs CIMMYT, Apartado Postal 6-641, 06600 Mexico D.F., Mexico across drought environments. Two such QTLs for GY, on chromosomes 1 and 10, coincided with two stable QTLs for KNO. Moreover, four genomic regions were identified for the expression of both GY and the anthesis-silking interval (ASI). In three of these, the allelic contributions were for short ASI and GY increase, while for that on chromosome 10 the allelic contribution for short ASI corresponded to a yield reduction. From these results, we hypothesize that to improve yield under drought, marker-assisted selection (MAS) using only the QTLs involved in the expression of yield components appears not to be the best strategy, and neither does MAS using only QTLs involved in the expression of ASI. We would therefore favour a MAS strategy that takes into account a combination of the “best QTLs” for different traits. These QTLs should be stable across target environments, represent the largest percentage possible of the phenotypic variance, and, though not involved directly in the expression of yield, should be involved in the expression of traits significantly correlated with yield, such as ASI

Applications of molecular markers in breeding

Molecular markers now provide appropriate complements to conventional breeding methods in most crops in ICRISAT’s germplasm conservation and crop improvement mandates. Where appropriate molecular markers are available, they are effective and sometimes appropriate, tools for crop improvement research addressing biological components in agricultural production systems. Molecular markers offer specific advantages in the assessment of genetic diversity and in trait-specific crop improvement. Molecular markers are almost infinitely superior to conventional morphological marker genes for mapping or tagging gene blocks associated with economically important traits. Gene tagging and QTL mapping in turn permit marker-assisted selection (MAS) in backcross, pedigree and population improvement programs, which can be especially useful for crop traits that are otherwise difficult or impossible to deal with by conventional means. Near-isogenic products of marker-assisted backcrossing programs can in turn provide not only improved cultivars, but also useful genetic tools facilitating improved understanding of mechanisms of abiotic stress tolerance or mechanisms of host plant resistance to pests and diseases that are critical components of integrated crop management systems. Finally, when relatively high-density marker-based fingerprinting of elite breeding lines is possible, this can be combined with pedigree information and multi-environment performance data sets to greatly enhance the ability of conventional breeding programs to design new cultivars, identify desirable recombinants, and track factors controlling complex traits and trait combinations

Molecular-Marker-Mediated Characterization of Favorable Exotic Alleles at Quantitative Trait Loci in Maize

Exotic maize (Zea mays L.) germplasm, shown to be useful for developing improved temperate cultivars, has remained little used partly because of many inherent shortcomings. Five F2 populations, developed from South American and U.S. germplasm, were used to detect favorable factors of exotic origin at quantitative trait loci (QTL) with isozymes and RFLPs. A number of traits of agronomic importance, including grain yield, were measured on F2 individuals and/or F3 families grown in several environments. Many QTLs, mostly with small effects, were identified. Major QTLs for grain yield and number of ears per plant were located on chromosomes 3 and 6. Stability of QTLs across environments was high. Favorable alleles of exotic origin were found at QTLs for several traits including grain yield and number of ears per plant. Most of these alleles also showed undesirable effects on other traits, however. Nevertheless, the superiority of exotic alleles over adapted alleles was demonstrated clearly at a few QTLs, re-affirming the usefulness of exotic germplasm for temperate maize breeding

Molecular identification of genetically distinct accessions in the USDA chickpea core collection

Knowledge of the molecular genetic variation of the accessions of core collections will be important for their efficient use in breeding programs, and for conservation purposes. The present study was undertaken for genotyping the part of the USDA chickpea core collection (Hannan et al 1994) with 20 microsatellite or simple sequence repeat (SSR) markers. In addition to understand the molecular diversity in the core collection, the genetic relationship was studied. A total of 376 accessions from the USDA chickpea core collection were genotyped. Twenty SSR markers revealed a total of 388 alleles among the 376 accessions. In the USDA core collection, the shared allele frequency (SAF) varied from 7.5% to 47.5% with an average of 21.6%. In the present study, the structure of the population was determined by using K=4 based on model-based (Bayesian) clustering algorithm

Progress in interspecific hybridization between Cicer arietinum and wild species C. bijugum.

This paper reports the production of hybrid plants between C. arietinum and C. bijugum in vitro and the transfer of hybrid plants to soil. Four chickpea cultivars, ICCV 92318, ICCV 2, ICCV 10 and KAK 2, were used as female parents. The wild species C. bijugum (accession ILWC 73) from germplasm collection at the International Centre for Agricultural Research in the Dry Areas, Aleppo, Syria, was used as male parent. Seeds of cultivated and wild chickpea were sown in the glasshouse and in the field in Andhra Pradesh, India. Crosses were carried out from October 2001 to February 2005 (4 postrainy seasons) in the field. Formation of viable green hybrid plants from the cross C. arietinum and C. bijugum with intermediate morphology between the two parents show that it is possible to obtain hybrid plants between C. arietinum and C. bijugum and that concerted efforts will yield hybrids in large numbers. Our study confirms that it is possible to cross C. bijugum with cultivated chickpea, and it would be feasible to produce a large number of hybrids to exploit the genes/traits present in C. bijugum for the improvement of cultivated species

Susceptibility of Four Tropical Lepidopteran Maize Pests to Bacillus thuringiensis CryI-Type Insecticidal Toxins

The relative susceptibility of 4 tropical maize pests, Spodoptera frugiperda (J. E. Smith),Diatraea grandiosella Dyar, D. saccharalis (F.), and Helicoverpa zea (Boddie), to the lepidopteran-specific CryI-type proteins produced by B. thuringiensis is presented. The toxin with the highest potency against H. zea larvae was the CryIAc toxin. S. frugiperda larvae were susceptible to CryID and CryIF toxins. The CryIB toxin showed to be highly toxic against D. grandiosella and D. saccharalis. This information will establish a basis for selecting B. Thuringiensis strains producing the appropriate CryI proteins to be used for the biological control of these tropical pests

Development, characterization and utilization of microsatellite markers in pigeonpea

Pigeonpea is a major legume of the semi-arid tropics that has been neglected in terms of molecular breeding. The objectives of this study were to develop microsatellite markers and evaluate their potential for use in pigeonpea genetics and breeding. Two hundred and eight microsatellite loci were isolated by screening a non-enriched partial genomic library. Primers were designed for 39 microsatellite loci, 20 of which amplified polymerase chain reaction products of the expected size. Nineteen of the primer pairs were polymorphic amongst 15 cultivated and nine wild pigeonpea accessions providing evidence for cross-species transferability within the genus Cajanus. A total of 98 alleles were detected at the 19 polymorphic loci with an average of 4.9 alleles per locus. The observed heterozygosity ranged from 0.17 to 0.80 with a mean of 0.42 per locus. Less allelic variation (31 alleles) was observed within the cultivated species than across the wild species (92 alleles). The diversity analysis readily distinguished all wild relatives from each other and from the cultivated germplasm. Development of more microsatellites is recommended for future genomic studies in pigeonpea

Genetic fingerprinting and aflatoxin production of \u3ci\u3eAspergillus\u3c/i\u3e section Flavi associated with groundnut in eastern Ethiopia

Background: Aspergillus species cause aflatoxin contamination in groundnut kernels, being a health threat in agricultural products and leading to commodity rejection by domestic and international markets. Presence of Aspergillus flavus and A. parasiticus colonizing groundnut in eastern Ethiopia, as well as presence of aflatoxins have been reported, though in this region, no genetic studies have been done of these species in relation to their aflatoxin production. Results: In this study, 145 Aspergillus isolates obtained from groundnut kernels in eastern Ethiopia were genetically fingerprinted using 23 Insertion/Deletion (InDel) markers within the aflatoxin-biosynthesis gene cluster (ABC), identifying 133 ABC genotypes. Eighty-four isolates were analyzed by Ultra-Performance Liquid Chromatography (UPLC) for in vitro aflatoxin production. Analysis of genetic distances based on the approximately 85 kb-ABC by Neighbor Joining (NJ), 3D-Principal Coordinate Analysis (3D-PCoA), and Structure software, clustered the isolates into three main groups as a gradient in their aflatoxin production. Group I, contained 98% A. flavus, including L- and non-producers of sclerotia (NPS), producers of B1 and B2 aflatoxins, and most of them collected from the lowland-dry Babile area. Group II was a genetic admixture population of A. flavus (NPS) and A. flavus S morphotype, both low producers of aflatoxins. Group III was primarily represented by A. parasiticus and A. flavus S morphotype isolates both producers of B1, B2 and G1, G2 aflatoxins, and originated from the regions of Darolabu and Gursum. The highest in vitro producer of aflatoxin B1 was A. flavus NPS N1436 (77.98 μg/mL), and the highest producer of aflatoxin G1 was A. parasiticus N1348 (50.33 μg/mL), these isolates were from Gursum and Darolabu, respectively. Conclusions: To the best of our knowledge, this is the first study that combined the use of InDel fingerprinting of the ABC and corresponding aflatoxin production capability to describe the genetic diversity of Aspergillus isolates from groundnut in eastern Ethiopia. Three InDel markers, AFLC04, AFLC08 and AFLC19, accounted for the main assignment of individuals to the three Groups; their loci corresponded to aflC (pksA), hypC, and aflW (moxY) genes, respectively. Despite InDels within the ABC being often associated to loss of aflatoxin production, the vast InDel polymorphism observed in the Aspergillus isolates did not completely impaired their aflatoxin production in vitro