Phenotypic and molecular characterization of a set of tropical maize inbred lines from a public breeding program in Brazil

Background The characterization of genetic diversity and population differentiation for maize inbred lines from breeding programs is of great value in assisting breeders in maintaining and potentially increasing the rate of genetic gain. In our study, we characterized a set of 187 tropical maize inbred lines from the public breeding program of the Universidade Federal de Viçosa (UFV) in Brazil based on 18 agronomic traits and 3,083 single nucleotide polymorphisms (SNP) markers to evaluate whether this set of inbred lines represents a panel of tropical maize inbred lines for association mapping analysis and investigate the population structure and patterns of relationships among the inbred lines from UFV for better exploitation in our maize breeding program. Results Our results showed that there was large phenotypic and genotypic variation in the set of tropical maize inbred lines from the UFV maize breeding program. We also found high genetic diversity (GD = 0.34) and low pairwise kinship coefficients among the maize inbred lines (only approximately 4.00 % of the pairwise relative kinship was above 0.50) in the set of inbred lines. The LD decay distance over all ten chromosomes in the entire set of maize lines with r2 = 0.1 was 276,237 kb. Concerning the population structure, our results from the model-based STRUCTURE and principal component analysis methods distinguished the inbred lines into three subpopulations, with high consistency maintained between both results. Additionally, the clustering analysis based on phenotypic and molecular data grouped the inbred lines into 14 and 22 genetic divergence clusters, respectively. Conclusions Our results indicate that the set of tropical maize inbred lines from UFV maize breeding programs can comprise a panel of tropical maize inbred lines suitable for a genome-wide association study to dissect the variation of complex quantitative traits in maize, mainly in tropical environments. In addition, our results will be very useful for assisting us in the assignment of heterotic groups and the selection of the best parental combinations for new breeding crosses, mapping populations, mapping synthetic populations, guiding crosses that target highly heterotic and yielding hybrids, and predicting untested hybrids in the public breeding program UFV.

A multi-part strategy for introgression of exotic germplasm into elite plant breeding programs using genomic selection

Some of the most economically important traits in plant breeding show highly polygenic inheritance. Genetic variation is a key determinant of the rates of genetic improvement in selective breeding programs. Rapid progress in genetic improvement comes at the cost of a rapid loss of genetic variation. Germplasm available through expired Plant Variety Protection (exPVP) lines is a potential resource of variation previously lost in elite breeding programs. Introgression for polygenic traits is challenging, as many genes have a small effect on the trait of interest. Here we propose a way to overcome these challenges with a multi-part pre-breeding program that has feedback pathways to optimise recurrent genomic selection. The multi-part breeding program consists of three components, namely a bridging component, population improvement, and product development. Parameters influencing the multi-part program were optimised with the use of a grid search. Haploblock effect and origin were investigated. Results showed that the introgression of exPVP germplasm using an optimised multi-part breeding strategy resulted in 1.53 times higher genetic gain compared to a two-part breeding program. Higher gain was achieved through reducing the performance gap between exPVP and elite germplasm and breaking down linkage drag. Both first and subsequent introgression events showed to be successful. In conclusion, the multi-part breeding strategy has a potential to improve long-term genetic gain for polygenic traits and therefore, potential to contribute to global food security.

Evaluation and participatory variety selection of improved highland sorghum varieties for smallholder farm at west hararghe zone

Participatory variety selection is the most important breeding program which enhanced the adoption of improved varieties through creating awareness based on smallholder farmers’ selection criteria. Several different improved sorghum varieties are released at different international and national research institutions at different times, however, the technologies were not properly addressed the farmers based on participatory, client oriented and demand driven. The experiment was carried out in West Hararghe Zone; Oromia Regional State, Ethiopia with the objective to identify and recommend the best adapted and performed improved sorghum varieties with farmers’ preference traits through continuous performance evaluation at different stages of the sorghum. A total of six sorghum varieties were evaluated in randomized complete block design in the 2019 main cropping season. Farmers have evaluated the entire experimental units using different statistical tools like direct-matrix and pair-wise ranking algorithms at maturity stage. Farmers set selection criteria to identify the superior improved varieties as compared to the local check by listing different agronomic traits like yield, biomass, seed color, seed size and biotic and abiotic resistance. The analysis of variance showed that there was highly significant difference (p<0.01) among the genotypes for all studied traits. The greatest grain yield was recorded from the variety Dibaba (11325 Kgha-1) and Jiru (10200 Kgha-1) respectively. Likewise, based on the overall farmer’s preference, Dibaba and Jiru were ranked first and second and followed by Adelle, ETS2752 and Chiro respectively. Additionally, the study revealed that participatory varietal selection is playing decisive role in gathering farmers’ perceptions, preferences, merits and shortcomings of sorghum varieties for future improvement. Hence, based on the result of the study, variety Dibaba and Jiru were recommended for multiplication and distribution to farmers through both formal and informal seed systems. Generally, the integration of plant breeders and farmers’ perceptions are used to increase the adoption rate and design a good breeding program for future improvement.

Genetic Variability Studies for Yield and Yield Contributing Traits in Rabi sorghum (Sorghum bicolor L. Moench) in Relation to Drought Tolerance

Genetic variability studies were useful for effective selection in a crop species. Presence of desirable variation and the amount of that variation which is heritable is the primary requirement of any breeding program for the crop improvement. Therefore any breeding program for crop improvement depends majorly on the knowledge pertaining to genetic variability, heritability and genetic advance. The genetic variability study was carried out for yield and yield contributing traits in thirty-seven genotypes of rabi sorghum with three checks namely M 35-1, Phule Suchitra and CSV-22-R at Sorghum Research Station, V.N.M.K.V., Parbhani during rabi 2019. A randomized block design was used with three replications and these treatments were evaluated and data pertaining to eleven traits were recorded with the objective to estimate the genetic variability for the quantitative traits. This investigation revealed presence of highly significant differences among the genotypes indicating presence of large amount of variability in all the eleven characters studied. The study indicated presence of higher estimates of phenotypic coefficient of variation (PCV) for all the traits when compared to genotypic coefficient of variation (GCV) and these estimates are of lower magnitude. Among the forty genotypes studied VJV 107, VJV 106, PEC 30, RSV 1921, RSV 1945 and RSV 1984 were considered as the superior genotypes as these recorded better performance. Higher estimates of GCV and PCV were recorded for the traits; days to 50 per cent flowering, plant height, panicle length, panicle width, fodder yield per plant, biological yield per plant, harvest index and grain yield per plant indicating selection for higher values of these traits of sorghum would be effective. Whereas high heritability coupled with moderate to high genetic advance was observed for traits like plant height, fodder yield per plant and total biomass per plant.

Backfat Thickness Does Affect the Restoration of Ovarian Activity Postpartum in Different Breeding Programs in Zebu Cattle

The backfat thickness (BFT) was used to forecast the onset of ovarian activity and predict the calf growth. Eighty Brahman cows with their calves were allocated in two groups of 40 distributed in 4 months according to the month of calving, starting in March and finishing in June. One was synchronized and inseminated at fixed time following by natural mating (TAI+NM); whilst the other only by natural mating (NM). The programs started at 60 ± 5 days postpartum and ended 60 days later. From day 30 postpartum, serial ultrasound examinations and progesterone samples were used to monitor the onset of ovarian activity. The BFT in the rump area was measured by ultrasound from 30 days postpartum and every 15 days thereafter. The weight of the calves was recorded at birth and at weaning on 160 days. The adjusted effect of BFT on ovarian activity and the calves' development was assessed by binomial logistic regression at 30, 60, 75, and 120 days postpartum. The cycling cows averaged higher BFT irrespective of breeding program (P &lt; 0.001). Also, slower changes in BFT were recorded during the follow-up at each time for all cows. However, the former had the higher BFT values from calving to the end of the study (P &lt; 0.001). At 60, 75, and 120 days, the BFT measured, at the preceding time, was the only factor predicting the commencement of cyclicity (P &lt; 0.001). The accumulative pregnancy through time was higher in TAI+NM (P = 0.003). Daily weight gain and weaning weight of the calves born in March was significantly heavier (P &lt; 0.001) than peers born in April, May, or June. The most critical element to forecast the onset of ovarian activity is the monitoring of BFT around calving regardless of the breeding program. BFT to estimate the development of the calves until weaning was unpredictable.

PEA (Pisum sativum L.) BREEDING: ADVANCES OF THE BREEDING PROGRAM AT UNIVERSIDAD NACIONAL DE ROSARIO

A pea breeding program to increase production in quantity and quality was started in 2005 in the College of Agrarian Sciences (FCA), National University of Rosario (UNR). The first steps were to gather an active collection of germplasm from around the world and to analyze genetic variability through morpho-agronomic and molecular traits in order to set objectives. In 2014, the National Institute of Agropecuarian Technology (INTA) and the FCA-UNR, joined forces to unite inter-institutional efforts for promoting the local development of pea genotypes adapted to the region. This program, using conventional methodologies, has so far obtained a new commercial line (Primogénita FCA-INTA) of green cotyledons, semi-leafless, with high adaptation to local agro ecological conditions and high yield potential. Breeding, nevertheless, is a slow process. Developing new pea varieties usually takes a decade or more when using traditional methodologies; thus, different alternatives were proposed for the reduction of this period. Doubled haploids and in vitro culture have been some of the methodologies developed; in pulses, however, they have not been efficiently implemented in breeding programs. In this context, Speed Breeding emerges as a technology that allows increasing the efficiency of the programs, while reducing costs and the required labor. Key words: peas, conventional methodologies, Speed Breeding, doubled haploids.