Combining higher accumulation of amylopectin, lysine and tryptophan in maize hybrids through genomics-assisted stacking of waxy1 and opaque2 genes

Waxy maize rich in amylopectin has emerged as a preferred food. However, waxy maize is poor in lysine and tryptophan, deficiency of which cause severe health problems. So far, no waxy hybrid with high lysine and tryptophan has been developed and commercialized. Here, we combined recessive waxy1 (wx1) and opaque2 (o2) genes in the parental lines of four popular hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) using genomics-assisted breeding. The gene-based markers, wx-2507F/RG and phi057 specific for wx1 and o2, respectively were successfully used to genotype BC1F1, BC2F1 and BC2F2 populations. Background selection with > 100 SSRs resulted in recovering > 94% of the recurrent parent genome. The reconstituted hybrids showed 1.4-fold increase in amylopectin (mean: 98.84%) compared to the original hybrids (mean: 72.45%). The reconstituted hybrids also showed 14.3% and 14.6% increase in lysine (mean: 0.384%) and tryptophan (mean: 0.102%), respectively over the original hybrids (lysine: 0.336%, tryptophan: 0.089%). Reconstituted hybrids also possessed similar grain yield (mean: 6248 kg/ha) with their original versions (mean: 6111 kg/ha). The waxy hybrids with high lysine and tryptophan assume great significance in alleviating malnutrition through sustainable and cost-effective means. This is the first report of development of lysine and tryptophan rich waxy hybrids using genomics-assisted selection.

Correlation between quantitative traits that affect grain yield of maize hybrids

The selection of pairs for hybridization requires knowledge about the correlation of the most important quantitative traits that affect grain yield of maize hybrids. The current study was carried out in the Agricultural Research Center “Donskoy” located in the south of the Rostov region with unstable moisture. The years of study (2018–2020) were arid (HThC 0.32–0.89). The purpose of the current study was to evaluate the correlation between quantitative traits and their influence on grain yield of maize hybrids under arid conditions. The objects of research were 96 interline maize hybrids. The analysis has identified the correlation between grain yield and such quantitative traits as ‘one maize ear weight’ (r = 0.64...0.87), ‘number of grains per one maize ear row’ (r = 0.37...0.75), ‘number of grains per maize ear’ (r = 0.32...0.51), ‘number of maize ears per plant’ (r = 0.41...0.53), ‘grain yield’ (r = 0.45...0.64). The traits ‘1000-grain weight’ and ‘number of grain rows’ had either no or slight effect on the formation of grain yield of maize hybrids (r = -0.12...0.28). There have been established the traits, the high values of which were well-combining in one genotype. The values of the trait ‘one maize ear weight’ raised due to an increase of the trait ‘number of grains per one maize ear row’ (r = 0.27...0.74), ‘number of grains per maize ear’ (r = 0.26...0.55), ‘grain yield’ (r = 0.21...0.52). The trait ‘number of grains per maize ear’ raised with an increase in the values of such constituent components as ‘number of grains per one maize ear row’ (r = 0.70...0.76), ‘number of grain rows per maize ear’ (r = 0.59...0.66), and also with an increase of ‘number of maize ears per plant’ (r = 0.32...0.51) and ‘grain yield’ (r = 0.36...0.38). There have been identified difficulty-combining quantitative traits, when the value of the trait ‘1000-grain weight’ decreased with the increase of the ‘number of grain rows per maize ear’ (r = – 0.18...-0.56), ‘number of grains per a maize ear row’ (r = -0.15...-0.31) and ‘grain yield’ (r = -0.01...-0.36).

Environmental Variability of Thousand Kernel Weight in Maize Hybrids of Different Maturity Groups

Thousand kernel weight (TKW) is an important yield component trait affected by the environmental conditions. This study’s objectives were to determine an environmental variability for the TKW in 32 maize hybrids, sorted in four FAO maturity groups (FAO300, 400, 500 and 600), and to compare 12 environments in Croatia (six locations in two years) according to the joint linear regression and stability analyses across the maturity groups. In general, the effects of the environment, genotype, and their interaction (GEI) were significant. A three-factor ANOVA revealed the greatest and highly significant year effect, while the location effect was non-significant across all four FAO groups. A stability analysis did not detect any preferences with regard to the locations and trends across the FAO groups. It indicates that all locations in the Pannonian region included in this study were suitable for an evaluation of the TKW in maize genotypes belonging to all maturity groups. The TKW seems to be an appropriate yield-component trait for maize breeding due to a high heritability and linear GEI nature.

Use of different criteria for estimating precocity of heterosis maize hybrids in forest-steppe conditions

In the article it is shown the results of the study of heterosis hybrids of corn on the signs of early ripening, such as: the growing season, the number of leaves on the main stem, the moisture yield of grain during harvest. To distribute our corn material by precocity, a number of studies were conducted, namely: estimating the length of the growing season "shoots – full ripeness", which was determined in days, and a very important indicator today is the moisture content of grain when harvested in percentage, it allowed to distribute heterosis hybrids into two groups: early-maturing (106–114) and middle-early – 114–123 days. Over the years of testing, the weather conditions varied considerably, which made it possible to evaluate in detail the material under study. In 2020, the growing season was within 107.8 days, which is almost three days less than in 2021. At the same time, the longer vegetation period was in 2021. Therefore, the aim of our study was to analyze the rate of moisture yield of corn grain of the studied hybrids of the two maturity groups. The conducted researches allowed to trace the dynamics of grain moisture yield of early-maturing maize hybrids and one hybrid of the middle-ripening group of maturity, to determine the variability of hybrid grain moisture in different periods of grain maturation. The year 2021 was more favorable for growing corn, the plants formed a large vegetative mass, but the grain had a high humidity during the harvest period. This is due to a significant amount of precipitation (69.9 mm) in August 2021. Hybrids that had high harvest humidity were characterized by a long growing season, such as № 47 × № 33. Therefore, our selected hybrids can be successfully used in planning a strategy for early maturity. In establishing the patterns of moisture transfer of grain when it reaches, in particular, the influence of the conditions of the year, in our study group were identified two hybrids consistently better in terms of grain moisture. Preference should be given to hybrids № 31 × № 37 and № 83 × № 125, which combine indicators of early maturity: the shortest growing season, the number of leaves on the main stem and the rate of moisture.

The variability of maize kernel drying: sowing date, harvest scenario and year

The extent of the reduction of maize (Zea mays L.) kernel moisture content through drying is closely related to field temperature (or accumulated temperature; AT) following maturation. In 2017 and 2018, we selected eight maize hybrids that are widely planted in Northeastern China to construct kernel drying prediction models for each hybrid based on kernel drying dynamics. In the traditional harvest scenario using the optimal sowing date (OSD), maize kernels underwent drying from 4th September to 5th October, with variation coefficients of 1.0–1.9. However, with a latest sowing date (LSD), drying occurred from 14th September to 31st October, with variation coefficients of 1.3–3.0. In the changed harvest scenario, the drying time of maize sown on the OSD condition was from 12th September to 9th November with variation coefficients of 1.3–3.0, while maize sown on the LSD had drying dates of 26th September to 28th October with variation coefficients of 1.5–3.6. In the future harvest scenario, the Fengken 139 (FK139) and Jingnongke 728 (JNK728) hybrids finished drying on 20th October and 8th November, respectively, when sown on the OSD and had variation coefficients of 2.7–2.8. Therefore, the maize kernel drying time was gradually delayed and was associated with an increased demand for AT ⩾ 0°C late in the growing season. Furthermore, we observed variation among different growing seasons likely due to differences in weather patterns, and that sowing dates impact variations in drying times to a greater extent than harvest scenarios.

Is Photoprotection of PSII One of the Key Mechanisms for Drought Tolerance in Maize?

Drought is one of the most important abiotic stress factors limiting maize production worldwide. The objective of this study was to investigate whether photoprotection of PSII was associated with the degree of drought tolerance and yield in three maize hybrids (30Y87, 31R88, P3939). To do this, three maize hybrids were subjected to three cycles of drought, and we measured the activities of photosystem II (PSII) and photosystem I (PSI). In a second field experiment, three maize hybrids were subjected to drought by withholding irrigation, and plant water status, yield and yield attributes were measured. Drought stress decreased leaf water potential (ΨL) in three maize hybrids, and this reduction was more pronounced in hybrid P3939 (−40%) compared to that of 30Y87 (−30%). Yield and yield attributes of three maize hybrids were adversely affected by drought. The number of kernels and 100-kernel weight was the highest in maize hybrid 30Y87 (−56%, −6%), whereas these were lowest in hybrid P3939 (−88%, −23%). Drought stress reduced the quantum yield of PSII [Y(II)], photochemical quenching (qP), electron transport rate through PSII [ETR(II)] and NPQ, except in P3939. Among the components of NPQ, drought increased the Y(NPQ) with concomitant decrease in Y(NO) only in P3939, whereas Y(NO) increased in drought-stressed plants of hybrid 30Y87 and 31R88. However, an increase in cyclic electron flow (CEF) around PSI and Y(NPQ) in P3939 might have protected the photosynthetic machinery but it did not translate in yield. However, drought-stressed plants of 30Y87 might have sufficiently downregulated PSII to match the energy consumption in downstream biochemical processes. Thus, changes in PSII and PSI activity and development of NPQ through CEF are physiological mechanisms to protect the photosynthetic apparatus, but an appropriate balance between these physiological processes is required, without which plant productivity may decline.

POSSIBILITIES OF DRIED DISTILLERS’ GRAINS WITH SOLUBLES APPLICATION IN FEED MIXTURES

The possibility of utilization of dried distiller’s grains with solubles (DDGS) in feed mixtures for feed production was investigated. Samples of maize hybrids ZP 548 and ZP 655b and DDGS obtained from hybrids ZP 548 and ZP 548c were used as components of the mixtures.The total protein content ranged from 12.42 % to 31.18 %, moisture from 5.49 % to 9.55 and ash content of 1.85 % to 4.37 %. The contents of NDF, ADF, ADL, hemicellulose and cellulose fibers ranged from: 13.90 % to 48.13 %; 2.96 % to 20.69 %; 0.27 % to 2.44 %; 10.69 % to 30.17 %, 2.62 % to 18.32 %, respectively. In vitro dry matter digestibility ranged from 55.20 % to 89.76 %. It was concluded that the samples of DDG obtained from red and yellow maize hybrids kernel are very suitable as components for the preparation of animal feed mixtures.

Nutritional Value of Whole Maize Kernels from Diverse Endosperm Types and Effects on Rheological Quality

Maize’s (Zea mays L.) nutrient content can be modified through selection. The objective of this study was to assess the nutritive value of 13 maize hybrids from four endosperm types, and the relationship between nutrient concentration, agronomic and rheological value. The hybrids were evaluated in two locations of Northwestern Spain over two years. There was genetic diversity among endosperm types and genotypes for all nutrients, with significant environmental effects, but few genotype × environment interactions. Flint hybrids had the highest protein and lipid content. The mutant wx1 significantly increased protein and reduced lipid, and both wx1 and o2 reduced ash and starch content and increased total fiber. Variability among hybrids within the wx1 endosperm was significant for most nutrients. Correlations between nutrients were rarely significant, implying that protein and lipid can be improved independently. Protein and lipid were negatively correlated with grain yield and plant height. However, improving nutrient content could alter agronomic performance, as nutrients had significant negative effects on rheological factors, particularly protein and lipid, which had negative effects on whole meal and on bread characteristics. Therefore, nutrient content can be improved in maize, but negative effects on agronomic and quality have to be taken into account.

Study of Combining Ability and Heterosis in Quality Protein Maize using Line x Tester Mating Design

Background: High protein content with good quality maize is likely to gain wider acceptance if hybrids are produced that have agronomic performance similar to normal hybrids and retain an enhanced nutritional quality. Thus, an attempt was made to develop quality protein maize hybrids for the benefit of different sections of society depending on maize. Methods: During the Rabi season of 2016-17 (hybrids were obtained crossing ten inbred lines and four testers following Line x Tester mating design) and 2017-18 (evaluation of hybrids and parents involved along with two commercial checks based on different agro-morphological traits). Result: Highly significant differences were observed among lines, testers and crosses. Combining ability revealed SCA variances was higher indicating preponderance of non-additive gene action. The contribution of line x tester interaction was higher suggesting parents used in this study can provide high heterotic cross combinations. The parents CML 508, CML 163-D and CML 169 were superior general combiners, indicating their efficacy as parents in future maize breeding programs. Heterosis identified superior yield advantage of the crosses namely, CML508 x CML154-2, CML170 x CML169 and CML163-D x DMRQPM103 over the standard commercial checks HQPM1 and 900 M Gold.