Fertilizer Effects on Endosperm Physicochemical Properties and Resistance to Larger Grain Borer, Prostephanus truncatus (Coleoptera: Bostrichidae), in Malawian Local Maize (Zea mays L.) Varieties: Potential for Utilization of Ca and Mg Nutrition

Maize grain hardness influences storage pest resistance, a key characteristic valued by smallholder farmers. The structural changes in the endosperm determine grain hardness and are influenced by agronomic practices. The purpose of this study was to establish whether supply of calcium and magnesium based fertilizers can alter physicochemical properties of local and hybrid maize varieties and reduce the infestation by larger grain borer (Prostephanus truncatus (Coleoptera: Bostrichidae)) during storage. Two local and one hybrid maize varieties commonly grown by smallholder farmers in Malawi were cultivated under three fertilizer treatments (NPK (nitrogen, phosphorous, potassium), NPK plus gypsum, and NPK plus dolomite). After harvest, the grains were classified into flint and dent types, followed by P. truncatus infestation and determination of their physicochemical properties. The addition of gypsum and dolomite fertilizers led to higher levels of amylose, total zein and β-14 zein, traits associated with kernel hardness, compared to the application of NPK fertilizer. Moreover, local maize varieties showed higher resistance to P. truncatus infestation, hardness and biochemical properties associated with hardness (total zein, α-19 and β-14 zein, starch lysophosphatidylcholine, and non-starch free fatty acid) compared to hybrid variety. Our study suggests the potential for utilizing Ca and Mg nutrition in maize to improve kernel hardness, thus adoption of gypsum and dolomite by smallholder farmers may be beneficial against P. truncatus during storage.

Novel Loci for Kernel Hardness Appeared as a Response to Heat and Combined Heat-Drought Conditions in Wheat Harboring Aegilops tauschii Diversity

Kernel hardness influences the milling and baking quality of wheat. Stress environments such as heat and combined heat-drought can produce harder kernels, thereby affecting the overall wheat quality. Beside puroindoline genes that are known to determine hardness, other QTLs contribute to the hardness. These QTLs, especially under stress conditions, need extensive research. Moreover, understanding the modification or stabilization of hardness under stress condition and the relationship with stress tolerance will facilitate the selection of superior lines that maintain both high yield and quality even under the stress environment. Therefore, in the current work, we aimed to identify the genetic loci and marker trait associations (MTAs) that contributes for hardness under optimum conditions in Japan, and heat and combined heat-drought (HD) conditions in Sudan. We used a panel of multiple synthetic derivatives (MSD) having diverse Aegilops tauschii genome segments and investigated the association between hardness stabilization and stress tolerance. Under stress conditions, we observed that less reduction of kernel weight is associated with either low change or stable kernel hardness. We identified 47 markers associated with hardness under all conditions; the D genome was the main contributor. For the first time, we found a significant association with hardness under stress conditions on chromosome 4D. We dissected several candidate genes associated with the change of hardness under stress conditions. Our results will improve the understanding of the genetic factors that affect wheat hardness stability.

The study of collection durum winter wheat samples according to grain quality in the Rostov region

The success of any agricultural crop breeding, including winter durum wheat primarily depends on the initial material at the breeder’s disposal, its value, and the degree of study. The purpose of the current study was to evaluate collection samples of winter durum wheat according to quality indicators and to select the best ones for use in breeding programs. In the Rostov region there were studied 159 winter durum wheat samples of different ecological and geographical origin according to grain quality (protein percentage, gluten content, amount of carotenoid pigments, kernel hardness, nature weight). The winter durum wheat samples had a high protein percentage and belonged to the 1-st quality class. According to gluten content in grain there were identified 17 (10.7%) samples. The following samples had the maximum values of trait ‘SDS-sedimentation’: ‘588/15’ (Russia) with 50 ml; ‘SAHINBEY’ (Turkey), ‘SARI BUGDAY 2’ (Turkey), ‘543/15’ (Russia) with 49 ml; ‘ANKARA 98’ (Turkey) with 48 ml. The following 43 winter durum wheat samples (more than 85%) had large kernel hardness in the trial: ‘663/17’, ‘1121/12’, ‘Novinka 4’, ‘Alena’ (Russia), ‘C1252’ (Turkey), ‘SN TURK MI 82-83 90 / GUTROS-2’, ‘DF 28.82.84 / DAB-18’, ‘P 1290493 // HUI // AV79’ (Mexico), ‘K-61869’ (Moldova). Over the years of study, a large amount of carotenoid pigments was identified in the following samples: ‘Novinka 4’ with 705 μg /%, ‘535/17’ with 689 μg /%, ‘543/15’ with 664 μg /% (Russia), ‘OSU-3880001 / 4AOS / SNIP / 3 / MEDIUM / KIF // SAPI’ with 704 μg /% (Mexico), ‘Winter Gold’ with 697 μg /% (Germany). According to the complex of qualitative indicators, there were identified 5 winter durum wheat samples, which are recommended to be included in the breeding programs of the Rostov region.

Toward the Genetic Basis and Multiple QTLs of Kernel Hardness in Wheat

Kernel hardness is one of the most important single traits of wheat seed. It classifies wheat cultivars, determines milling quality and affects many end-use qualities. Starch granule surfaces, polar lipids, storage protein matrices and Puroindolines potentially form a four-way interaction that controls wheat kernel hardness. As a genetic factor, Puroindoline polymorphism explains over 60% of the variation in kernel hardness. However, genetic factors other than Puroindolines remain to be exploited. Over the past two decades, efforts using population genetics have been increasing, and numerous kernel hardness-associated quantitative trait loci (QTLs) have been identified on almost every chromosome in wheat. Here, we summarize the state of the art for mapping kernel hardness. We emphasize that these steps in progress have benefitted from (1) the standardized methods for measuring kernel hardness, (2) the use of the appropriate germplasm and mapping population, and (3) the improvements in genotyping methods. Recently, abundant genomic resources have become available in wheat and related Triticeae species, including the high-quality reference genomes and advanced genotyping technologies. Finally, we provide perspectives on future research directions that will enhance our understanding of kernel hardness through the identification of multiple QTLs and will address challenges involved in fine-tuning kernel hardness and, consequently, food properties.

Genomics-Enabled Analysis of Puroindoline b2 Genes Identifies New Alleles in Wheat and Related Triticeae Species

Kernel hardness is a key trait of wheat seeds, largely controlled by two tightly linked genes Puroindoline a and b (Pina and Pinb). Genes homologous to Pinb, namely Pinb2, have been studied. Whether these genes contribute to kernel hardness and other important seed traits remains inconclusive. Using the high-quality bread wheat reference genome, we show that PINB2 are encoded by three homoeologous loci Pinb2 not syntenic to the Hardness locus, with Pinb2-7A locus containing three tandem copies. PINB2 proteins have several features conserved for the Pin/Pinb2 phylogenetic cluster but lack a structural basis of significant impact on kernel hardness. Pinb2 are seed-specifically expressed with varied expression levels between the homoeologous copies and among wheat varieties. Using the high-quality genome information, we developed new Pinb2 allele specific markers and demonstrated their usefulness by 1) identifying new Pinb2 alleles in Triticeae species; and 2) performing an association analysis of Pinb2 with kernel hardness. The association result suggests that Pinb2 genes may have no substantial contribution to kernel hardness. Our results provide new insights into Pinb2 evolution and expression and the new allele-specific markers are useful to further explore Pinb2’s contribution to seed traits in wheat.

HARDNESS OF SPRING DURUM WHEAT KERNELS IN THE WEST SIBERIA

There have been presented study results of the spring durum wheat varieties grown in the southern forest-steppe area of the Omsk region on kernel hardness. The objects of research were the varieties of ecological variety testing conducted by various Russian and Ukrainian scientific institutions. The study was conducted in the period from 2003–2015. Experimental plots of 10 m2 were placed in 4 sequences. The varieties were sown in weedfree fallow. The soil of the experimental plot was weakly leached blackearth (chernozem), medium humus (6.2%), and loamy. The sowing date is 14–15 of May, the sowing rate is 4.5 million of germinated kernels per ha. The average hardness index in 2003–2015 was 70.1%. The varieties varied from 66.0 (the variety “Svetlana”) to 74.6% (the variety “Saratovskaya zolotistaya”). The differences between maximum and minimum were 8.6%. The variation through the years was from 51% to 92%, from 21% (the varieties “Angel”, “Omsky korund”) to 34% (the variety “Saratovskaya zolotistaya”). The calculated coefficient of variation showed that the variability degree ranged from little to medium. Coefficients of variation varied from 9.3% (the variety “Angel”) to 14.3% (the variety “Bezenchukskaya 182”). According to S. A. Eberhart, W. A. Russel the stability index indicates a lower variability of the varieties “Angel”, “Omsky korund”, “Altayskaya niva”, “Nik”, “Kharkovskaya 23”, “Tavolga”. The value of the regression coefficient (bi) for kernel hardness ranged from 0.77 to 1.23. The varieties “Voronezhskaya 9”, “Elizavetinskaya”, “Altayskaya niva”, “Omskaya stepnaya” and “Bezenchukskaya stepnaya” turned to be most responsive to the conditions (according to the Eberhart – Russell test). The varieties “Angel”, “Aleyskaya”, “Zarnitsa Altaya” had a weak reaction to the environmental conditions. There has been identified phenotypic correlation between the trait and productivity, 1000-kernel weight, nature weight, gluten quality, pasta color. The correlation between these traits is positive, on average r = 0.30–0.440.