APOE ε4 effects on hippocampal atrophy in the healthy elderly reflect future cognitive decline

The APOE ϵ4 allele is the primary genetic risk factor for late onset Alzheimer's disease (AD). A cardinal problem in determining APOE ϵ4's effect on cognition and brain structure in older individuals is dissociating prodromal changes — linked to increased AD risk — from potential phenotypic differences. To address this, we used cognitive and neuroimaging data from a large cohort of cognitively normal 69-86 year-olds with up to 8 yearly follow-ups to investigate cross-sectional and longitudinal differences between APOE ϵ3/ϵ3 homozygotes and ϵ3/ϵ4 heterozygotes. Although we found a significant age-by-genotype interaction in right hippocampal volume, once our analyses were conditionalised by future diagnosis to account for prodromal mild cognitive impairment (MCI) and AD, this effect was no longer observed. Likewise, longitudinally, rate of hippocampal atrophy was determined not by genotype, but by future diagnosis. Thus, we provide direct evidence in support of the prodromal hypothesis of APOE ϵ4 on brain structure.

Yield and Disease Responses of Improved Groundnut Genotypes Under Natural Disease Infection in Northern Uganda: Implication for Groundnut Disease Management

Groundnut production in Uganda is constrained by groundnut rosette disease (GRD), the main cause of yield loss experienced by farmers. We conducted the current study to assess the responses of improved groundnuts to diseases (rosette and late leaf spot) and yield under local conditions. Four released groundnut genotypes (Serenut 5R, Serenut 8R, Serenut 9T and Serenut 14R) were evaluated in four locations in northern Uganda for two seasons in 2019. We established the experiment following randomised complete block design with three replications. GRD severity (harvest) and late leaf spot (LLS) severity (harvest) on the four genotypes were not significantly (P > 0.05) different but positively correlated with the Area Under Disease Progress Curve (AUDPC). Genotype-by-location interaction for LLS AUDPC, GRD AUDPC and dry pod yield were significant (P < .001). Season-by-genotype interaction was not significant (P = 0.367). Days to 50% flowering were also not significant (P > 0.05). Highest and lowest yields were recorded for Serenut 9T in the Omoro district (1,291 kg/acre) and the Amuru district (609 kg/acre), respectively. Dry pod yield was significantly (P < 0.001) negatively correlated with GRD severity and GRD AUDPC. Yield performance of the four genotypes was not significantly (P < 0.05) different in the districts, except for Kitgum, where yields of Serenut 9T and Serenut 8R were significantly (P < 0.05) higher. These genotypes could be used to manage GRD by smallholder farmers in Northern Uganda. Special consideration should therefore be given to these four groundnut genotypes for GRD management in the Acholi sub-region.

Oil content and fatty acid profile of selected poppy (Papaver somniferum L.) landraces and modern cultivars

The oil content and fatty acid composition were determined in the seed of 19 poppy genotypes (both landraces and modern cultivars) grown in three-year field trials. The total oil content ranged from 34.56–44.76%. The oil content in white-seeded genotypes (40.73–44.76%) exceeded the oil content in blue-seeded genotypes (34.56–40.34%) and ocher-seeded genotypes (38.36–42.69%). Linoleic acid (71.41–74.02%), oleic acid (12.35–15.51%) and palmitic acid (8.95–10.29%) were the most abundant fatty acids in the evaluated seeds of poppy genotypes. A significant negative correlation (–0.7574**) was found between linoleic and oleic fatty acids. The sum of polyunsaturated (PUFA), monounsaturated (MUFA) and saturated (SFA) fatty acids ranged from 72.43–74.91%, 12.90–16.14% and 10.99–12.46% of the total fatty acids, respectively. Both the total oil content and the content of individual fatty acids were mainly affected by the crop year (weather conditions); however, the effect of genotype and year × genotype interaction was also significant. Due to the favourable composition of fatty acids, the evaluated poppy genotypes can be<br /> a good source of nutritionally valuable oil.

In Vitro-in Vivo Digestibility and Nitrogen Balance in Indigenous, Exotic and Crossbred Growing Pigs Fed Sprouted or Roasted Cowpea Diets

The study evaluated effects of processing cowpeas for inclusion in maize-based diets for Windsnyer, Large-White x Landrace, and their 3-way crossbred growing pig genotypes. In-vitro, the raw and roasted cowpea diets, sprouting cowpeas decreased (P<0.05) gastric-ileal non-enzymatic (buffer-only) DM digestibility. Roasting increased (P<0.05) the colon enzymatic digestion relative to sprouting. Total ileal and colon in-vitro diet DM digestibility were not affected (P>0.05) by cowpea processing. In-vivo, Pigs consumed most (P<0.05) feed (g/day/kg BW) in period 1, with significant (P<0.05) genotype X period interaction. Both roasting and sprouting cowpeas reduced (P<0.05) dietary apparent DM digestibility. Pig daily body weight (BW) gain reduced (P<0.05) in period 3 compared to period 1. There was no (P>0.05) treatment effect on feed conversion efficiency. The 3-way crossbred pigs excreted more (P<0.05) urine N (g/dayBW0.75). Urine N excretion (g/dayBW0.75) peaked (P<0.05) in period 2 (P<0.05), with less (P<0.05) N intake (g/dayBW0.75), faecal N excretion (g/dayBW0.75) and N balance (g/dayBW0.75) than in period 3. Significant diet X genotype interaction in faecal N excretion (g/dayBW0.75) resulted from markedly high (P<0.05) in contrast to low (P<0.05) excretion. Significant genotype X period interaction resulted from the numerically (P>0.05) higher urine N excretion. In conclusion, in-vitro, sprouting shifted non-enzymatic digestion to the colon, while roasting increased colon fibrolysis, without effect on overall DM digestibility. In-vivo, the period of feeding, interpreted to reflect pig maturity, the pig genotype and cowpea processing interacted to influence apparent dietary DM digestibility and N utilization, without significant effect on the conversion efficacy of the maize-cowpea diet.

Analysis of Diversity And Identification of SSR, SCoT, And ITAP Informative Amplicons For Grain Fe And Zn Content In Wheat Genotypes

Biofortification provides a promising method of solving microelement malnutrition in developing countries. For this purpose, a study was conducted to understand the grain Fe and Zn content variation in seventy prevalent Iranian wheat genotypes across three consecutive years, to assess genetic diversity, and to identify informative amplicons for high grain Fe and Zn content using three simple sequence repeat (SSR), start codon targeted (SCoT) polymorphism, and intron targeted amplified polymorphism (ITAP) markers. Grain Fe and Zn content was highly variable each year with high heritability. Despite the highly significant effect of year-genotype interaction, some stable genotypes were ranked highly all the three years for grain Fe and Zn content. The grain Fe and Zn contents were positively correlated in the second and third years. High genetic diversity was detected among the wheat genotypes using three different marker systems. A number of informative SSR, SCoT, and ITAP amplicons for high grain Fe and Zn were identified overall or in individual years. A few informative amplicons were common and stable for grain Fe and Zn content in the different years. The SSR alleles located on 3A, 4A, 4B, and 6B chromosomes were positively correlated with high Fe and Zn content, indicating that co-location of genes affected Fe and Zn content. Identification of informative alleles and amplicons for high grain Fe and Zn content could contribute to the development of sequence-based markers and improve the selection of genotypes with high micronutrient content.

Performance of elite genotypes of barley, chickpea, lentil, and wheat under conservation agriculture in Mediterranean rainfed conditions

Conservation agriculture (CA) practices are becoming more important in Mediterranean rainfed areas due to their potential to minimize climatic risk, reduce soil erosion, and improve soil quality and water availability. Due to minimum soil disturbance and crop residue retention, the soil environment for crop growth and development can differ between CA and conventional tillage (CT) practice. However, breeding targets for improving yield performance in CA system remain poorly explored. The objective of this study was to assess the performance of elite genotypes of barley, chickpea, lentil, and wheat grown under CA, a promising alternative agricultural practice in the Mediterranean rainfed conditions. A three-year field study, with contrasting rainfall pattern, was conducted in the International Center for Agriculture Research in the Dry Areas’s research field in Morocco to evaluate the tillage × genotype interaction and its consequence for yield performance of barley, chickpea, lentil, and wheat. Thirteen elite genotypes for each crop were planted under both CA and CT systems. Wheat and chickpea produced significantly higher grain yield (+62% for wheat and +43% for chickpea) under CA than in CT, while lentil and barley performed equally under both systems. Significant effect of tillage × genotype was more frequent for chickpea and wheat than for barley and lentil. Increased yield under CA, mainly in dry year, was associated with higher harvest index (HI). For each crop species yield was mainly influenced by rainfall amount and distribution (75–88% yield variation), and tillage × genotype was of little importance. The overall results suggest that a specific breeding program for CA in lentil, chickpea, wheat, and barley may not be efficient. Few tillage × genotype interaction, especially in dry years, indicated that breeding target on increasing HI, tolerance to drought (high yield in dry years), and potential yield (high yield in wet year) can help to improve yield performance of chickpea, lentil, and wheat genotypes in CA system. Varieties with wider adaptability considering drought tolerance, higher yield with stability, and adoption of CA practices are important in the context of the Mediterranean rainfed environment. Integrating trade-off analysis between yield potential and stability in a rainfall gradient in both CT and CA in the national certification scheme of varieties may be more efficient than developing breeding programs for each type of tillage system.

Legume tasters: symbiotic rhizobia host preference and smart inoculant formulations

Mutualistic interactions have great importance in ecology, with genetic information that takes shape through interactions within the symbiotic partners and between the partners and the environment. It is known that variation of the host-associated microbiome contributes to buffer adaptation challenges of the host’s physiology when facing varying environmental conditions. In agriculture, pivotal examples are symbiotic nitrogen-fixing rhizobia, known to contribute greatly to host (legume plants) adaptation and host productivity. A holistic view of increasing crop yield and resistance to biotic and abiotic stresses is that of microbiome engineering, the exploitation of a host-associated microbiome through its rationally designed manipulation with synthetic microbial communities. However, several studies highlighted that the expression of the desired phenotype in the host resides in species-specific, even genotype-specific interactions between the symbiotic partners. Consequently, there is a need to dissect such an intimate level of interaction, aiming to identify the main genetic components in both partners playing a role in symbiotic differences/host preferences. In the present paper, while briefly reviewing the knowledge and the challenges in plant–microbe interaction and rhizobial studies, we aim to promote research on genotype x genotype interaction between rhizobia and host plants for a rational design of synthetic symbiotic nitrogen-fixing microbial communities to be used for sustainably improving leguminous plants yield.