Lines Of Grain Sorghum Research Articles

Research on Genotype Markers for Plant Height and Assisted Breeding of Key Sorghum Resources in China.

Dwarfing and the selection of optimal plant types constitute the primary focus of sorghum breeding. However, the lack of clarity regarding the gene types associated with plant height genes Dw1-Dw4 in the primary breeding materials has led to increased plant heights in improved offspring of the same plant height type, resulting in unsatisfactory morphological traits. This study aimed to elucidate the gene types related to plant height in breeding materials, validate the regulatory mechanisms, and establish a material improvement system. The goal was to achieve molecular-marker-assisted dwarf breeding through the detection of plant height genes and the test cross verification of main Chinese sorghum materials. Using 38 main male sterile lines and 57 main restorer lines of grain sorghum as materials, three plant height genes were detected and classified. Ninety-five F1 generation hybrids of these materials, along with typical materials, were measured at the wax maturity stage. Test cross results demonstrated that the variation in dw1-dw3 genes in the breeding materials significantly influenced the plant height of hybrid offspring. The main male sterile lines in Chinese sorghum predominantly exhibited the "three-dwarf" type of Kafir and its improved lines, characterized by the genotype (Dw1-Dw2-dw3-dw4). On the other hand, restorer lines mainly showcased the improved "two-dwarf" (Dw1-Dw2-dw3-dw4) genotype of the Kaoliang/Caudatum subspecies, along with the "three-dwarf" type of some Kafir and its improved lines. The test materials predominantly contained dw3 genes, with relatively fewer dw1 genes in the restorer lines. The primary restorer materials lacked the dw2 gene, and dw2 significantly influenced plant type. The increased plant height in improved offspring of the same plant height type material was attributed to differences in gene types. Therefore, the enhancement of plant height in breeding materials should prioritize the use of different methods in conjunction with Dw1 and Dw2 classification.

Variability of the main breeding traits of sorgo CMS lines depending on the weather conditions of the Saratov region

Determining the nature of the interaction between the genotype and the environment is one of the critical stages of breeding practice for selecting effective parental forms of hybrids of the first generation of sorghum and their stable seed reproduction in the arid conditions of the Saratov region. The contribution of regulated and unregulated factors to the overall variability of a trait can be determined using a two-factor analysis of variance used in this work. The research objects were 11 sterile lines of grain sorghum grown on the experimental field of the Federal State Budgetary Research Institution RosRISM (Russian Research Institute of Sorghum and Maize) “Rossorgo” during 2009–2018. The meteorological conditions of plant cultivation varied significantly: in 2013 and 2017, they were characterised as sufficiently humid (Hydrothermal coefficient - HTC = 0.98–1.01), 2011 – acutely dry (HTC = 0.26), other years – dry (HTC = 0.45–0.68). As a result of the tests, it was found that the CMS lines differed in economically valuable traits. The sterile line A1 Efremovskoe 2 should be classified as tall (131.2 cm) and more productive (4.41 t/ha of seeds) with a well-developed leaf apparatus (the area of the giant leaf is 238.0 cm2). Low-growing CMS lines M35 and 9E Pishchevoe 614 (94.9–98.5 cm) were distinguished by the protrusion of the inflorescence stem - 21.6 cm, and A3, A4 and 9E Zheltozernoe 10 (109.8–110.2 cm) - with a long leaf (50.7–51.5 cm). Medium-sized lines A2 Vostorga and A4 KP 70 had a long inflorescence (23.0–24.5 cm), while A3 Feterita 14 had a short inflorescence (13.7 cm). It was found that the genotype (41.4–61.6%) had a more substantial effect on the overall variability of plant height, length and protrusion of the stem of the inflorescence, and leaf length, while the environmental factor had a more substantial effect on seed yield (55.3%).

Breeding value of drought-resistant sterile sorghum lines

Currently, breeders often use multidimensional statistics methods to process a large set of experimental data. To characterize the breeding value of 20 sorghum lines with cytoplasmic male sterility (CMS lines) under arid cultivation conditions, during the research there was applied a cluster analysis, allowing to group the lines into clusters according to similar indicators from 15 analyzed agronomic and physiological characteristics. The studies were carried out during 2019-2021, various in meteorological conditions: the hydrothermal coefficient was 0.59-0.84 during the vegetation period of plants. Cytoplasmic male sterility lines were sown at a density of 100 thousand plants per 1 hectare. Breeding and physiological traits were evaluated according to generally accepted methods. The assessment of agronomic and physiological characteristics was carried out according to generally accepted methods. For further practical work, based on the results of the conducted studies, four CMS lines of grain sorghum (clusters 2, 3, 5) were identified according to a complex of physiological and breeding characteristics. Sterile lines (A2 Vostorg, M35-1А Pischevoe 614, A3 Feterita 14 and A2 KVV 114) were distinguished by the highest seed yield of 3.02-3.50 t/ha, high water content (72.7-73.7 %) and water retention capacity of leaves (72.2-84.3 %), low water deficiency (6.5-8.7 %). The study of moisture loss during the natural wilting of leaves confirmed the high resistance to drought in the flowering phase of the sterile A2 KVV 114 line, in which the intensity of moisture loss after 1 hour was only 9.9 %, 1.5 h – 15.8 % and 24 h – 68.6 %. In breeding for increasing drought resistance the CMS-line A1 Efremovskoe 2 (the sixth cluster) should be noted, as it was inferior to the above-described lines only in terms of low water deficiency (16.5 %), indicating average drought resistance. The line is the tallest with large leaves (length – 46.7 cm, area – 163.8 cm2) and form 3.21 t/ha of seeds on average for the period presented. The use of the obtained data provides the increasing of the breeding process for the creation of productive drought-resistant F1 sorghum hybrids.

Assessment of drought resistance in sorghum CMS lines based on various sterility sources

Background. Global climate changes have recently led to a more frequent occurrence of adverse factors and a decrease in the productivity of major crops. Sorghum is a highly drought-resistant crop that can tolerate long-term soil and air droughts with much lower harvest losses than wheat or barley. It is important to understand physiological mechanisms affecting drought tolerance when breeding efforts are aimed at improving the adaptability to abiotic conditions and productivity of sorghum hybrids.Materials and methods. Twenty sterile lines of grain sorghum with 8 types of CMS were studied in 2019 and 2020 in the arid conditions of Saratov Province. Indicators of the leaf water regime were assessed according to VIR’s guidelines. Statistical processing of the research results was performed using the AGROS 2.09 software.Results. The indicators of the leaf water regime that reflected differentiated responses of the CMS-line plants to the prevailing water and temperature stressors during the critical flowering period for sorghum were analyzed. Four CMS lines were identified according to the chosen set of indicators: they manifested 71.13–72.02% of total water content, 5.26–9.08% of water deficit, and 57.40–83.17% of water retention capacity on average for the two years of research. For the first time, the effect of CMS in sorghum on the manifestation of water regime indicators was registered. In isonuclear CMS lines, the greatest effect on drought resistance was shown by cytoplasm A3 versus A4 (with the Zheltozernoe 10 genome), cytoplasm A5 versus A1 (with the Karlik 4v genome), and M35-1A versus the analog on cytoplasm 9E (with the Pischevoe 614 genome).Conclusion. It is shown that genetically different types of sterility can be used in breeding practice to increase the resistance to abiotic stressors in components of F1 crosses and hybrids.

Stem vacuole-targetted sucrose isomerase enhances sugar content in sorghum

BackgroundSugar content is critically important in determining sugar crop productivity. However, improvement in sugar content has been stagnant among sugar crops for decades. Sorghum, especially sweet sorghum with high biomass, shown great potential for biofuel, has lower sugar content than sugarcane. To enhance sugar content, the sucrose isomerase (SI) gene, driven by stem-specific promoters (A2 or LSG) with a vacuole-targetted signal peptide, was transformed into the sorghum inbred line (T×430).ResultsThe study demonstrated that transgenic lines of grain sorghum, containing 50–60% isomaltulose, accumulated up to eightfold (1000 mM) more total sugar than the control T×430 did (118 mM) in stalks of T0 generation. Subsequently, the elite engineered lines (A5, and LSG9) were crossed with sweet sorghum (Rio, and R9188). Total sugar contents (over 750 mM), were notably higher in F1, and F2 progenies than the control Rio (480 mM). The sugar contents of the engineered lines (over 750 mM), including T0, T1, F1, and F2, are surprisingly higher than that of the field-grown sugarcane (normal range 600–700 mmol/L). Additionally, analysis of physiological characterization demonstrated that the superior progenies had notably higher rates of photosynthesis, sucrose transportation, and sink strength than the controls.ConclusionsThe genetic engineering approach has dramatically enhanced total sugar content in grain sorghum (T0, and T1) and hybrid sorghum (F1, and F2), demonstrating that sorghum can accumulate as high or higher sugar content than sugarcane. This research illustrates that the SI gene has enormous potential on improvement of sugar content in sorghum, particularly in hybirds and sweet sorghum. The substantial increase on sugar content would lead to significant financial benefits for industrial utilization. This study could have a substantial impact on renewable bioenergy. More importantly, our results demonstrated that the phenotype of high sugar content is inheritable and shed light on improvement for other sugar crops.

Study of the adaptive capacity of CMS-lines of grain sorghum in the conditions of the Lower Volga region

Relevance. In the arid conditions of the lower Volga region, studies were conducted to identify different response rates of CMS lines of grain sorghum in order to use them in the selection of hybrids for resistance to abiotic stressors.Material and methods. The adaptive capacity of maternal forms was studied on the example of 12 CMS lines (obtained using sterility sources A1, A2, A3, A4, M-351A, 9E) at the experimental field of institute in 2014–2018. The plot area is 7.7 m2. The density of standing plants is 100 thousand plant/ha. Repeatability in the experience — three times. The calculation of adaptability indicators was carried out using the program for statistical processing of experimental data Agros 2.09.Results. It is established that the formation of a biomass productivity of sterile lines, the predominant influence of the interaction of genotype with year terms, which amounted to 58.2 per cent, while the factors of genotype and the year conditions contribute 31,0 and 10.8%, respectively. At the same time, the influence of the hydrothermal coefficient for the period of “germination-maturation” of sorghum on the productivity of biomass is confirmed by a positive linear relationship (y = 1,903x + 13.90). Among the studied forms, CMS lines A1 O-Yang 1 and A2 Tamara with a biomass yield of 10.33–14.08 t/ha are characterized by high stress resistance and average variability of the trait. Highyielding female forms A3 Feterita 14 and A1 Efremovskoe 2 (18.34–20.71 t/ha) have high indicators of stability index (3.97–6.30), genetic flexibility (16.55–20.70), which indicates their greater adaptability to the arid conditions of the region. These sterile lines are recommended to be included in the program of crosses when creating productive F1 hybrids.

Influence of different types of sterile cytoplasms (A3, A4, 9E) on the combining ability of CMS lines of sorghum.

Investigation of the effect of the cytoplasm on the combining ability (CA) of lines with cytoplasmic male sterility (CMS) is of considerable interest in terms of understanding the genetic functions of the cytoplasm and for practical purposes to create hybrids with improved economically valuable traits. In order to investigate the effect of different types of sterile cytoplasm (A3, A4, 9E) on CA in sorghum, we studied the manifestation of a number of biological and agronomic traits in 54 F1 hybrid combinations obtained using iso-nuclear CMS lines with the nuclear genome of the line Zheltozernoye 10, differing only in the types of sterile cytoplasm (A3, A4 and 9E). Eighteen varieties and lines of grain sorghum developed at the Russian Research and Project-technological Institute of Sorghum and Maize were used as paternal parents. The CA was determined by the topcross method. F1 hybrids and their parents were grown in 2015–2017 in conditions of insufficient (2015–2016: HTC (hydro-thermal coefficient) = 0.32–0.66), or good water availability conditions (2017: HTC = 1.00). On average, for three years of testing, a positive effect of the 9E cytoplasm on the general combining ability (GCA) (0.63) and negative effects of the A3 and A4 cytoplasms (–0.32 and –0.31) for the inflorescence length were noted. In dry seasons, significant positive effects of the 9E cytoplasm on GCA for the length of the largest leaf, and positive effects of the A3 cytoplasm on GCA for the plant height, and negative effects of the A4 cytoplasm on GCA for these traits were observed. No differences were observed during the wet season. The type of CMS did not affect the GCA for the width of the largest leaf and grain yield. The dispersion of specific combining ability (SCA) in the dry seasons was significant for the following traits: leaf length, plant height, panicle length and width, and grain yield, the 9E cytoplasm had the highest SCA dispersion, whereas the A4 cytoplasm had the smallest one. The data obtained indicate that different types of sterile cytoplasm of sorghum make a different contribution to CA under conditions of drought stress.

ASSESSMENT OF THE CORRELATION OF INTERRELATIONS OF MORPHOLOGICAL CHARACTERISTICS OF THE GRAIN SORGHUM

In modern conditions, the need for cultivation of grain sorghum in regions with insufficient moisture is determined by its high yield and grain quality. For practical breeding, with the objective of assessing linkages 19 morphological and physiological traits model of the population including 15 varieties and 2 promising lines of grain sorghum that is created in the Russian Research and Design Technological Institute of Sorghum and Maize. The biochemical composition of the grain of the objects of research is presented graphically.
 A different degree of variation in the characteristics of grain sorghum was revealed: very strong (V> 40,0%) - productive bushiness, number of grains from 1 panicle; strong (20,0% <V <40,0%) - the width of the panicle, the extension of the panicle leg, the thickness of the upper internode, the area of the flag leaf, the area of the fourth on top of the leaf, the mass of the grain from 1 panicle; weak (V <10,0%) - the height of the plants after 30 days, the height of the plants during maturation. The group with an average degree of variation (10.0% <V <20.0%) includes all other signs measured in the experiment. Factor analysis was used to optimize, interpret the calculated matrix of correlation coefficients. In the analysis of the correlation coefficient matrix, hypothetical factors with a contribution of more than 5% to the accumulated variance are calculated. The first hypothetical factor is determined by the high effects of morphophysiological features. The second factor is largely due to the contribution of plant height 30 days after germination and the extension of the panicle legs. Plant height at maturity, weight of 1000 grains make the greatest contribution to the third factor. The width of the panicle makes the greatest contribution to the accumulated dispersion of the fourth factor. The fifth factor is determined by the effects of plant height at the beginning and end of vegetation, as well as the total contribution of all studied features.

Epicuticular wax and its effect on canopy temperature and water use of Sorghum

Epicuticular wax is thought to enable sorghum [Sorghum bicolor (L.) Moench] plants to cope with drought. Increased reflectivity of solar radiation and reduced conductance of water vapor are mechanisms responsible for aiding plants in water conservation. Increased reflectivity should lead to a decrease in canopy temperature and water use, whereas decreased conductance should lead to an increase in canopy temperature because of a decrease in evaporative cooling. It is not clear how these competing effects exert control over water use in a crop such as sorghum. To better understand the role of epicuticular waxes on the energy balance of sorghum, experiments were conducted to determine the effects of waxes on field-scale energy fluxes using near-isogenic lines of grain sorghum having different levels of epicuticular wax loading. Waxes caused an overall 2% increase in albedo, and about 86% of the reflected energy between 400 and 1100 nm was from near-infrared wavelengths. This is at variance with recent reports that suggest that waxes can substantially increase the reflectivity of sorghum. Instead, our results indicated that the amount of reflected radiant energy due to waxes was small. When water was non-limiting, waxes caused a 22% decrease in canopy conductance compared to a 2% increase in albedo on average. Consequently, at the expense of higher canopy temperatures, waxes caused a 5% reduction in latent heat flux when water was not limiting. Without rain, water became limiting to plants with lower wax load sooner than it did for plants with higher wax load. The high wax load canopy then was on average 0.4 °C cooler, had 24% greater canopy conductance and 13% greater latent heat fluxes compared to the low wax one. Results suggested that the primary mechanism through which waxes affect the energy balance of sorghum is by means of reduced conductance of water vapor.

Creation and study of raw material for grain sorghum breeding

For the arid zone of the Lower Volga region, grain sorghum is an important forage crop. The paper presents the results of a comparative assessment of grain yield and biomass of breeding lines of grain sorghum in the nursery of preliminary variety testing. The volume of the nursery for the preliminary variety testing was 117 breeding lines. The most productive were the breeding lines of grain sorghum, the grain yield of which reached 3.95 t / ha (line PSI-17 / EV-56); 4.10 t / ha (line PSI-17 / EV-113); 4.15 t / ha (line PSI-17 / EV-55); 4.50 t / ha (line PSI-17 / EV-92) with a yield of 3.75 t / ha of the standard variety Volzhskoe 4. As a result of scientific research, the promising breeding lines of grain sorghum were identified: PSI-17 / EV-56 and PSI-17 / EV-92, which were recommended to be submitted for competitive variety testing. It is advisable to use the breeding line of grain sorghum PSI-17 / EV-54V for early maturity. The breeding lines of grain sorghum: PSI-17 / EV-56 and PSI-17 / EV-90 are planned to be included in crosses to create varieties and hybrids with high grain quality. Breeding lines of grain sorghum: PSI-17 / EV-50, PSI-17 / EV-54, PSI-17 / EV-92 and PSI-17 / EV-127 are planned to be used in breeding for biomass yield.

The study of morphophysiological and economically valuable traits and properties of variety samples of grain sorghum

The results of studying 32 variety samples and lines of grain sorghum are presented, as well as experimental data on the genotypes of vegetative and generative traits, and the biochemical composition of grain. When considering the elements of the structure of the grain sorghum crop, we proceeded from the understanding that the yield is directly dependent on the number of grains per 1 m2 and their mass of 1000 grains. Since the plant standing density was the same for all the studied samples, genotypes with a large mass of grains of 1 plant were noted (k-3568, k-3867, k-3900, k-3904, k-8926), which depends on the number of productive stems per plant and weight of 1000 grains. The following cultivars are characterized by the largest mass of 1000 grains: k-3568, k-3900, k-3904, k-3911, k-3962, k-3967, k-3970, k-8926. The average weight of grains from 1 panicle varied in the range from 14.1 to 22.7 g, and the biological grain yield was 3.69 ... 6.19 t / ha (with a grain moisture content of 13%). The output of gross energy for cattle is from 3.99 to 6.69 energetic feed unit. Energy assessment and feed value are determined by the biochemical composition of the grain. In the experiment, variety specimens with high protein content were revealed: k-3902, k-3946, k-3959, k-3970. More than 4.0% of fat was detected in the grain of the variety samples: k-3867, k-3911, k-3957, k-3967, k-3970, k-3973.

СЕЛЕКЦИЯ ЗЕРНОКОРМОВЫХ КУЛЬТУР В УСЛОВИЯХ ПОВОЛЖЬЯ

With the aim of creating varieties forage-grain directions for a ten years, conducted a comprehensive assessment of 80 lines of grain sorghum, 55 lines of sweet sorghum, 70 lines of Sudan grass and 15 varieties and lines of foxtail millet. The result of testing new lines of grain sorghum on the complex biological and economic-valuable signs of breeding lines L-211, L-226 and L-355, which on average over the five years exceeded the grade standard at the studied signs. These lines will be submitted for State variety testing. By results of studying breeding material of sweet sorghum 4 identified promising lines which significantly standard cultivar Volzhskoe 51 in the complex of signs and properties. Breeding lines of sweet sorghum: L-109, L-1106 L-1327, L-1898/2 and L-84 were recommended for further evaluation in the competitive variety trial . Long-term study of initial material for breeding Sudan grass allowed identifying promising lines of L-67, L-730 and L-14, which for five years had a high breeding performance. Thus, on the basis of years of scientific research created a unique working collection for breeding crops. All prospective line will be used in the final stages of the selection process, and included in the crossing for obtaining hybrids of grain and forage sorghum. According to the results of selection obtained the copyright certificate and the patent for the cultivar Anastasia foxtail millet and copyright certificate for the grade of the grain sorghum Garant. For State trials in 2015, passed a variety of Sudan grass Eugene.

<b> <i>In situ</i> degradability of dry matter and fibrous fraction of sorghum silage

This study aimed to evaluate in situ degradability and degradation kinetics of DM, NDF and ADF of silage, with or without tannin in the grains. Two isogenic lines of grain sorghum (CMS-XS 114 with tannin and CMS-XS 165 without tannin) and two sorghum hybrids (BR-700 dual purpose with tannin and BR-601 forage without tannin) were ensiled; dried and ground silage samples were placed in nylon bags and introduced through the fistulas. After incubation for 6, 12, 24, 48, 72 and 96 hours, bags were taken for subsequent analysis of fibrous fractions. The experimental design was completely randomized with 4 replicates and 4 treatments and means compared by Tukey’s test at 5% probability. As for the DM degradation rate, silage of CMSXS165without tannin was superior. Silages of genotypes BR700 and CMSXS 114 with tannin showed the highest values of indigestible ADF (59.54 and 43.09%). Regarding the NDF, the potential degradation of silage of CMSXS165 line without tannin was superior. Tannin can reduce ruminal degradability of the dry matter and fibrous fractions.

Combining ability and mode of inheritance of stem thickness in forage sorghum (Sorghum bicolor L. Moench) F1 hybrids

Aim of this research was determination of mode of inheritance, gene effects components of genetic variance, combining abilities, average contribution of lines and testers and their interactions in expression of stem thickness in forage sorghum F1 generation. Method line x tester was applied. Material comprised of eight genetically divergent A-inbred lines of grain sorghum three R lines-testers of Sudan grass and twenty-four F1 hybrids obtained by crossing lines with testers. Among tested genotypes there were significant differences in mean values of stem thickness. Analysis of variance of combining abilities showed that there were highly significant differences for general combining abilities (GCA) and specific combining abilities (SCA) non-additive component of genetic variance (dominance and epistasis) had greater portion in total genetic variance for stem thickness. During the first research year, interaction between inbred maternal line with testers had the largest contribution in expression of stem thickness of F1 hybrid at both locations, while in the second year at location Rimski Šančevi the largest contribution belongs to lines and at location Mačvanski Prnjavor the largest contribution belongs to testers. Assessment of combining abilities showed that these inbred lines of grain sorghum can be used as mothers: SS-1 646, SS-1 688 and S-8 682 in breeding forage sorghum for thicker stem. According to SCA, promising forage sorghum hybrids are S-8 682 x ST-R lin H and P-21 656 x C-198. This research can be of importance for developing new high-yielding forage sorghum hybrids.

Genetic analysis of feed quality and seed weight of sorghum inbred lines and hybrids using analytical methods and NIRS

Summary Eight lines of grain sorghum and their F1 hybrids were evaluated for contents of crude protein (CP), fat (FAT), and starch (STA); protein digestibility (PD); and in vitro dry matter disappearance (IVDMD). The effect of seed weight (SW) on these traits and the potential use of near infrared reflectance spectroscopy (NIRS) to predict them also were investigated. The male lines included three normal-seeded lines (TX2737, TX435, and P954063) and two largeseeded lines (PL-1 and Eastin1). The female lines included common U.S. seed parent lines (Wheatland, Redlan, and SA3042). The lines and their hybrids were grown under dryland conditions at Kansas State University experiment fields in Ashland and Belleville, Kansas, in 1999. The experiments were conducted using a randomized complete block design with four replications at each location. The effect of genotype was significant for all measured traits. The male parent lines were highly variable and expressed high levels of genetic variation in combining ability for CP, PD, STA, and SW. The female parents were genetically more uniform; however, significant general combining ability effects were noted for PD and SW. Significant negative correlations were noted between CP and STA and between SW and STA. Significant positive correlations were found between CP and SW and between FAT and IVDMD. Crude protein content was predicted accurately by NIRS. Fat content and IVDMD could not be predicted by NIRS. The NIRS equations based on ground samples were more accurate than those based on whole-seed samples.

Germination, Emergence, and Yield of 20 Plant–Color, Seed–Color Near‐Isogenic Lines of Grain Sorghum

Although there is growing demand for sorghum [Sorghum bicolor (L.) Moench] with white seed and tan plant color, there is limited information on the overall agronomic fitness of sorghum with these characters. A set of experiments was conducted to evaluate the combined effects of plant color and seed color on sorghum germination, emergence, and agronomic performance. Twenty near‐isogenic lines with red seed/tan plant (RT), red seed/purple plant (RP), white seed/tan plant (WT), white seed/purple plant (WP) phenotypes were tested under field and laboratory conditions. Plant color × seed color interactions were not significant. Purple plant color phenotypes had higher cold germination, higher germination after accelerated aging, and greater seedling elongation at 10 d than tan plant color phenotypes. Plant color did not influence standard warm germination. No differences in standard warm germination or seed vigor test results were attributable to seed color. Seedling emergence under field conditions was higher for the red seed than the white seed phenotype. Grain yield was higher for the white seed than the red seed phenotype, and higher for the purple plant color than the tan plant color phenotype. Grain test weights from purple plant color lines were higher than those from tan plant color lines. All four phenotypes included relatively high yielding lines. There was considerable overlap between WT, WP, RT, RP lines in yield and other indicators of agronomic performance leading to the conclusion that white seed and tan plant color lines with comparable performance to red seed and purple plant color lines can be selected from segregating breeding populations.

Pathotoxin‐Induced Alteration in Protein Synthesis Associated with Susceptibility of Sorghum to Milo Disease

Symptoms of milo disease of sorghum, Sorghum bicolor (L.) Moench, caused by the fungus, Periconia circinata (Mangin) Sacc., can be elicited selectively in susceptible genotypes by treatment with the host‐specific toxin produced by the fungus. Sorghum lines with diverse genetic backgrounds were examined to determine whether disease susceptibility is correlated with an enhanced rate of synthesis of 16‐kilo dalton proteins induced by the toxin. Test materials included near‐isogenic susceptible and resistant lines of grain sorghum ‘Colby’, susceptible and resistant selections of shattercane, toxin‐sensitive selections from China and Nigeria, and spontaneous resistant mutants of Colby. Protein synthesized in root tips after treatment with the toxin were labeled in vivo with [3H]‐leucine, separated by polyacrylamide gel electrophoresis, and detected by fluorography. Toxin treatment enhanced the rate of synthesis of the 16 kD proteins in all susceptible selections but not in any of the resistant selections. These results establish a correlation between susceptibility of sorghum to P. circinata and an increased rate of synthesis of 16 kD proteins induced by the host‐specific toxin from P. circinata.

Diallel Analysis of Aluminum Tolerance in Selected Lines of Grain Sorghum1

A half‐diallel cross involving three Al‐tolerant and three Al‐sensitive sorghum genotypes as identified through a screening test was used to study the inheritance of Al tolerance in grain sorghum [Sorghum bicolor, (L.) Moench]. Data from the Ft generation and parents were analyzed using the Grilllng and the Jinks‐Hayman methods of diallel analyses. Highly significant general combining ability (GCA) and specific combining ability (SCA) effects were observed for the Al‐tolerance trait. The GCA effects were much more important than SCA effects, the ratio being 9:1. From the Vr‐Wr graph, the Al‐tolerance trait showed predominantly additive genetic effects with some degree of dominance. The six parents fell into four groups according to the relative level of dominance: (i) highly dominant (AK 3010, 182), (ii) moderately dominant (NB 9040), (iii) moderately cessive (‘Texas Blackhull Kafir’), and (iv) highly recessive 3001 and AK 3006). The average degree of dominance was partial. Heritability of Al‐tolerance in the genotypestudied was high. Narrow‐sense and broad‐sense heritabilities were 78 and 99%, respectively. The additive gene action and the high heritability for this trait should make either pedigree breeding or recurrent selection successful for the development of Al‐tolerant grain sorghum inbreds.

Performance and stability of mixtures of grain sorghum

In the absence of intergenotypic interactions the expected yield of randomly constituted, equiproportional mixtures of genotypes is shown to be independent of the number of components. However, with positive, additive interactions, the expected yield of a mixture is expected to be a monotonically increasing function of the number of components. The observed relationship between level of genetic diversity and mean yield, seed number and seed size for mixtures of inbred lines of grain sorghum closely followed the relationships expected under the assumption of additive interaction effects. However, estimates of the first and higher order components of the total interaction effect among the sorghum lines indicated that higher order interaction effects were often as great or greater than their first order counterparts, and opposite in sign, and that they may thus have had a cancelling effect in mixtures containing three or more components. These findings are discussed in terms of the relationship between level of genetic diversity and performance, and in connection with problems associated with the development of commercial multiline varieties.

Interrelations Among Agronomic Characters in Grain Sorghum (Sorghum bicolor Moench)1

Genotypic and phenotypic correlations among 12 characters were estimated in segregating populations and in pure lines of grain sorghum (Sorghum bicolor Moench). Grain yield was positively and significantly correlated with head weight, kernel number, half bloom date, and leaf number, but negatively correlated with germination percentage and protein percentage. The inverse relationships between kernel weight and kernel number, and between kernel weight and head number per plant may arise from developmentally induced relationships or be genetically dependent. Head weight and half bloom date are considered best indicators for yield, while germination percentage may be of value as an indicator for protein content. Magnitudes of the estimates of expected progress in improving yield by selecting for characters other than yield appear to be greater than those for protein, indicating that direct selection for protein may be more effective in improving protein content.