Components of resistance to the sorghum midge, Contarinia sorghicola

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible cultivars (CSH 1 and Swarna). Data were recorded on the numbers of eggs, larvae, emerged adults and grain damage in panicles of different genotypes infested with 60 midge females/panicle under no-choice conditions. The size of floral parts (glume, lemma, palea, lodicule, stigma, style, ovary and anther), rate of grain development and tannin content of grain were measured. The lengths of glume gl and 82, lemma L1 and L2, palea, lodicule, anther, style and stigma were positively associated with susceptibility to sorghum midge. Rate of grain development (between 3rd and 7th day after anthesis) was negatively associated with susceptibility to sorghum. Tannin content of grain was also negatively correlated with midge susceptibility, although there were distinct exceptions (e.g. DJ 6514 is highly resistant bur has a low tannin content).     

高粱穗部主要性状的配合力分析

以4个高粱不育系13163A、1358A、128A和407A,以及6个恢复系9.1R、213R、272R、381R、矮182R和早21R为试验材料,按照不完全双列杂交设计(NCII),对其F1的穗部主要性状进行配合力分析。结果表明:亲本穗部主要性状存在显著的遗传差异,主要表现为加性基因效应遗传的性状有:穗长、一级枝梗数、二级枝梗数、穗粒数;狭义遗传力大小顺序分别为:二级枝梗数一级枝梗数穗长穗粒数穗粒重千粒重。不同亲本的一般配合力(GCA)和特殊配合力(SCA)在不同穗部性状间存在较大差异。不育系407A和恢复系早21R、9.1R是综合性状较好的亲本材料,利用它们可组配出产量较高的杂交组合。恢复系272R组配的杂交种具有穗粒数较多、千粒重较小的特点,能满足市场上对小粒高粱的需求。深入分析高粱杂交亲本穗部主要性状表现,有利于对亲本材料的进一步了解和利用。     

Interactions between panicle size, insect density, and environment for genotypic resistance in sorghum to head bug,Calocoris angustatus

Studies were undertaken on interactions between panicle size, insect density, host plant, and the environment for sorghum head bug,Calocoris angustatus Lethiery on five sorghum genotypes in terms of bug population increase, grain damage and loss in grain mass across four panicle sizes (5, 10 or 20 branches/panicle and whole panicle), and three infestation levels (5, 10 and 15 pairs of bugs/panicle). Head bug numbers increased and grain damage decreased with an increase in panicle size in the head bug susceptible cultivars, CSH 1 and CSH 5. However, the increase in bug numbers or decrease in grain damage was not significant in head bug resistant genotypes, IS 17610 and IS 17645. Head bug numbers increased with an increase in infestation level in CSH 1 and CSH 5, however, such an increase was not substantial in IS 17610 and IS 17645. Grain damage was significantly lower in IS 17610 and IS 17645 compared with CSH 1 and CSH 5 across infestation levels. Head bug population increased at a greater rate during the rainy season compared with the dry season. Panicle size and infestation levels accounted for greater variation in grain damage and percentage loss in grain mass during the rainy season than in the dry season. To identify reliable sources of resistance to insects, it is important to study insect host plant-interactions across panicle sizes (levels of food availability), infestation levels and seasons.     

Efficacy of neem pesticides on whorl larva,stem-borer and panicle insect pests of sorghum in Nigeria

Two field trials were conducted from 2003 to 2005 on the effects of neem pesticides on whorl larva, stem-borer and panicle pests of sorghum. In the first trial (2003–2004) the effect of neem seed granules (NSG) and carbofuran (furadan 3G®) inserted into the sorghum whorl at 30, 40 and 50 days after sowing (DAS) were tested on whorl larva, stem borer and grain yield. Results showed that NSG and carbofuran significantly (P ≤ 0.01) reduced whorl larva feeding, leaf puncturing and chaffy panicle, and significantly (P ≤ 0.01) increased grain yield compared with untreated check. In the second trial, (2004–2005), aqueous neem seed extract (ANSE), neem seed oil (NSO) and deltamethrin (Decis 12 EC®) were sprayed at anthesis and grain filling stages. Results also showed that the three pesticides significantly (P ≤ 0.01) reduced insect damage and also significantly (P ≤ 0.01) increased grain yield by 28.3% (deltamethrin), 19.4% (NSO) and 17.9% (ANSE) above the yield of check. It is suggested that neem pesticides may be suitable as alternatives to synthetic pesticides for the management of sorghum whorl larva, stem borers and panicle insect pests in the Nigerian Sudan savannah.     

Antifungal Proteins during Sorghum Grain Development and Grain Mould Resistance

Proteins potentially inhibitory to the growth of grain‐moulding fungi in vitro have been identified from sorghum seeds. However, their role in vivo during fungi infection is still not clear. The objective of the present study was to evaluate the presence of antifungal proteins (AFPs) during grain development. Sureño (a grain mould‐resistant line), RTx430 (a grain mould‐susceptible) and their F₁ hybrid, were planted at two moisture levels. Caryopses were collected from each genotype every 7 days after anthesis (DAA) during development and maturity of the grain. Significant levels of grain mould occurred naturally. Levels of four AFPs (sormatin, chitinases, β‐1,3‐glucanases and ribosomal‐inactivating proteins) were determined using the immunoblotting technique. During grain development (7–35 DAA), Sureño and the F₁ hybrid showed higher levels of sormatin and chitinase than RTx430. RIPs levels in Sureño and the F₁ hybrid were higher than those in RTx430 after 21 DAA. Sormatin, chitinases, β‐1,3‐glucanases and RIPs levels in Sureño and in the F₁ hybrid were higher than those of RTx430 after grain physiological maturity. AFPs are associated with grain mould resistance because Sureño and the F1 hybrid induce and/or retain higher AFPs levels under grain mould infection pressure than did RTx430.     

Seasonal incidence of Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) and its parasitoids on Sorghum halepense (L.) Pers. in south-eastern Queensland, Australia

Abstract  To quantify the role of Johnson grass, Sorghum halepense , in the population dynamics of the sorghum midge, Stenodiplosis sorghicola , patterns of flowering of Johnson grass and infestation by sorghum midge were studied in two different climatic environments in the Lockyer Valley and on the Darling Downs in south-eastern Queensland for 3 years. Parasitism levels of S. sorghicola were also recorded. In the Lockyer Valley, Johnson grass panicles were produced throughout the year but on the Darling Downs none were produced between June and September. In both areas, most panicle production occurred between November and March and infestation by S. sorghicola was the greatest during this period. The parasitism levels were between 20% and 50%. After emergence from winter diapause, one to two generations of S. sorghicola developed on S. halepense before commercial grain sorghum crops were available for infestation. Parasitoids recorded were: Aprostocetus diplosidis , Eupelmus australiensis and two species of Tetrastichus. Relationships between sorghum midge population growth rate and various environmental and population variables were investigated. Population size had a significant negative effect ( P  < 0.0001) on population growth rate. Mortality due to parasitism showed a significant positive density response ( P  < 0.0001). Temperature, rainfall, open pan evaporation, degree-days and host availability showed no significant effect on population growth rate. Given the phenology of sorghum production in south-eastern Queensland, Johnson grass provides an important bridging host, sustaining one to two generations of sorghum midge. Critical studies relating population change and build-up in sorghum to sorghum midge populations in Johnson grass are yet to be performed.     

Evaluation of planting date, sorghum hybrid, and insecticide treatment on sorghum midge (Diptera: Cecidomyiidae) management in northeast Louisiana

The combined effect of planting date, insecticide treatment, and host-plant resistance was studied in northeast Louisiana for management of the sorghum midge, Stenodiplosis sorghicola (Coquillett), during 1994 and 1995. Significantly higher numbers of sorghum midges were observed visiting flowering spikelets of the midge-susceptible sorghum hybrid (Delta and Pine Land 'DP1552') than those of the midge-resistant sorghum hybrid (DeKalb 'DK-60'). Numbers of midges averaged 1.2 and 0.6 per flowering panicle in the susceptible and resistant sorghum hybrids, respectively, in 1994 and 1.8 and 1.0, respectively, in 1995. Midge densities increased significantly as the sorghum flowering season progressed. Sorghum midge reached peak densities during the first half of August in 1994 and 1995. The length of the flowering period in the early-planted (mid-March) sorghum was significantly longer compared with the flowering periods in the mid-April, mid-May, or mid-June planted sorghums. This resulted in prolonged exposure of flowering panicles to ovipositing midges and increased midge damage in the early-planted (mid-March) sorghum. Damage by sorghum midge was significantly higher in the early-planted (mid-March) sorghum hybrids than in the late-planted (mid-June) sorghum hybrids. The midge-susceptible hybrid produced highest yields when planted in mid-April and mid-May (optimum period) and lower yields when planted very early (i.e., mid-March) or late (i.e., mid-June). No significant differences were observed in yields for the resistant hybrid at any planting date in 1994. However, in 1995, significantly lower yields were recorded in resistant sorghum planted in mid-June. Levels of sorghum midge damage and sorghum seed yields in the untreated resistant hybrid were not significantly different than those observed in the insecticide-treated susceptible hybrid. Numbers of adult midges captured on sticky traps were positively correlated to numbers of visual estimates of ovipositing midge females visiting flowering spikelets.     

Influence of sorghum maturity on abundance and damage potential of Banks grass mite,Oligonychus pratensis (Banks)

This research was designed to study the effects of sorghum maturity on abundance and damage potential of Banks grass mite,Oligonychus pratensis (Banks). More mites per plant were recorded on the latest maturing line (M100) and the least on the early maturing lines (60M and CK60). Mite densities on B407 (late maturity) did not differ from any of the lines tested. Mite densities were positively correlated with leaf area. In contrast, mite feeding damage was significantly lower on the late maturing lines, demonstrating that sorghum susceptibility to mite feeding increases as plants reach anthesis and caryopsis.     

Effect of sorghum resistant to Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) on oviposition and development of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Abstract Helicoverpa armigera oviposition preference for, and larval development on sorghum hybrids with differing resistance to sorghum midge, Stenodiplosis sorghicola , were investigated. When H. armigera larvae were fed seed of resistant and susceptible hybrids in the laboratory there were no differences in larval and pupal sizes or the rate of development. The same result was recorded when larvae fed on panicles on plants in a glasshouse. On some sampling occasions, significantly more eggs were laid on panicles of resistant hybrids in the field. This occurred when plants were in plots and also in a mixed planting. Midge-resistance status did not affect levels of egg parasitism. In a field study using recombinant inbred lines between a midge-resistant and a midge-susceptible line, no relationship was found between level of resistance and oviposition of H. armigera . We conclude that, although midge-resistant hybrids are sometimes preferred for oviposition by H. armigera, the resistance per se does not determine this preference. Egg survival, larval survival, development and resultant damage are not significantly affected by the midge-resistance status of the host.     

Infection biology and defence responses in sorghum against Colletotrichum sublineolum

Aims:  To investigate the infection biology of Colletotrichum sublineolum (isolate CP2126) and defence responses in leaves of resistant (SC146), intermediately resistant (SC326) and susceptible (BTx623) sorghum genotypes.
Methods and Results:  Infection biology and defence responses were studied quantitatively by light microscopy, H₂O₂ accumulation by DAB staining and HRGP accumulation by immunological methods. Inhibition of conidial germination and appressorium formation may represent prepenetration defence responses on the leaf surface. Inducible defence responses in the resistant genotypes included decreases in formation of appressoria as well as accumulation of H₂O₂, HRGPs and phytoalexins. Concomitant with these inducible responses, fungal growth was stopped during or just after penetration in genotypes SC146 and SC326. High levels of H₂O₂ accumulating at late infection stages (5 days after inoculation) in the susceptible genotype BTx623 correlated with necrosis and tissue degeneration.
Conclusions:  The early accumulation of H₂O₂ and HRGPs indicates roles in defence whereas the late accumulation in genotype BTx623 correlated with successful pathogenesis.
Significance and Impact of the Study:  The fact that there is a significant correlation between induced accumulation of H₂O₂, papilla formation and cell wall cross-linking, as evidenced by HRGP accumulation, and cessation of pathogen growth in resistant genotypes may help exploit host resistance in sorghum.     

Regulation of leaf senescence, grain-filling and yield of rice by kinetin and abscisic acid

Senescence of rice ( Oryza sativa L. cv. Jaya) leaves was regulated with kinetin and abscisic acid (ABA) sprays at the reproductive stage. The effect of such sprays on grain-filling and yield was analyzed. Spraying 100-day-old plants with kinetin solution (100 μg ml^-1) significantly delayed senescence as indicated by higher total chlorophyll and protein levels in the three uppermost leaves compared with the controls. In contrast, spraying with ABA (15 μg ml^-1) significantly promoted foliar senescence. The number of spikelets per panicle, number of panicles, percentage filled grains, panicle weight and grain yield per plant and the mobilization and harvest indices were significantly increased by kinetin treatment, while ABA decreased most of them. The possibility of increased grain-filling and thus, yield due to delayed foliar senescence by kinetin treatment and decreased grain-filling due to hastening of senescence by ABA is discussed.     

Rice responses to drought under carbon dioxide enrichment. 1. Growth and yield

Projections of future climate change include a strong likelihood of a doubling of current atmospheric carbon dioxide concentration ([ CO ₂]) and possible shifts in precipitation patterns. Drought stress is a major environmental limitation for crop growth and yield and is common in rainfed rice production systems. This study was conducted to determine the growth and grain yield responses of rice to drought stress under [CO₂] enrichment. Rice (cv. IR-72) was grown to maturity in eight naturally sunlit, plant growth chambers in atmospheric carbon dioxide concentrations [CO₂] of 350 and 700 μmol CO₂ mol^–1 air. In both [CO₂], water management treatments included continuously flooded (CF) controls, flood water removed and drought stress imposed at panicle initiation (PI), anthesis (ANT), and both panicle initiation and anthesis (PI & ANT). The [CO₂] enrichment increased growth, panicles plant^–1 and grain yield. Drought accelerated leaf senescence, reduced leaf area and above-ground biomass and delayed crop ontogeny. The [CO₂] enrichment allowed 1–2 days more growth during drought stress cycles. Grain yields of the PI and PI & ANT droughts were similar to the CF control treatments while the ANT drought treatment sharply reduced growth, grain yield and individual grain mass. We conclude that in the absence of air temperature increases, future global increases in [CO₂] should promote rice growth and yield while providing a modest reduction of near 10% in water use and so increase drought avoidance.     

Antifungal Effect and Protective Role of Ursolic Acid and Three Phenolic Derivatives in the Management of Sorghum Grain Mold Under Field Conditions

In this study, investigation was carried out under in vitro as well as field conditions to explore inhibitors of sorghum grain mold. Phytochemicals, viz., methyl trans‐p‐coumarate (AIC‐1), methyl caffeate (AIC‐2), syringic acid (AIC‐3), and ursolic acid (UA), at different concentrations (500, 750, and 1000 ppm) were tested on spore germination of Alternaria alternata, Curvularia lunata, Fusarium moniliforme, F. pallidoroseum, and Helminthosporium sp. Significant growth inhibition (P < 0.001) was observed against all fungi except A. alternata which was found to be resistant to AIC‐3. Further, two separate sets of field experiments involving spraying of water and F. moniliforme suspension over chemicals treated (1000 ppm) sorghum panicles were done. The levels of protection varied with different treatments which were graded using a standard 1 – 9 rating scale. The Fusarium‐challenged panicles (FCP) showed lesser susceptibility and decreased the rate of infection of grain mold (grade 7.0), compared to simple UA, AIC‐2, and AIC‐1 treatments (7.4, 7.6, and 8.0 grade, resp.). The HPLC quantification of differentially induced phenolic acids in treated sorghum grains substantiated this effect disclosing the higher accumulation of chlorogenic, vanillic, and salicylic acids in FCP. This might be due to defensive induction of these acids by the plants. Although mold control by examined chemicals were lesser than the standard Tilt (grade 5.9), they were found to be nontoxic to mammalian cells under cytotoxicity assay.     

Additive effects of three auxins and copper on sorghum in vitro root induction

A healthy root system is vital for tissue culture plantlet survival and rapid adaptation from the in vitro microenvironment to glasshouse conditions. Optimization of the root induction medium is an effective way to promote root induction and elongation. Levels of three auxins (α-naphthaleneacetic acid [NAA], 3-indoleacetic acid [IAA], and 3-indolebutyric acid [IBA]) and copper sulfate (CuSO₄) have been investigated in a series of experiments with a sorghum inbred line, Tx430. Significant improvement in root proliferation and shoot growth were observed on Murashige and Skoog (MS) medium supplemented with 1 μmol/L CuSO₄, 1 mg/L NAA, 1 mg/L IAA, and 1 mg/L IBA. On average, one explant (the original in vitro-derived shoot) of Tx430 regenerated 56.7 roots, which was 20-fold higher on the optimal medium than on MS control medium. Another tested genotype SA281 showed similar response patterns as Tx430 across media. In addition, 100% of Tx430 and SA281 plantlets originating from the optimized root induction medium all survived after being transferred to potting soil in the glasshouse. The results demonstrate that a combination of auxins (NAA, IAA, and IBA) and CuSO₄ together at optimal concentrations provide additive effects on promoting root proliferation and explant growth of in vitro sorghum in root induction medium, and subsequently resulted in 100% survival rate of plantlets ex tissue culture. Compared with two published and frequently used root induction media, the optimized medium significantly enhanced root induction and plantlet growth.     

Response of near‐isogenic sorghum lines,differing at the P locus for plant colour,to grain mould and head smut fungi

Leaves and stalks of many sorghum genotypes accumulate dark red or purple pigments upon wounding while some plants, called ‘tan,’ do not. Grains with unpigmented ‘white’ pericarps grown on tan plants are more desirable for food. The hypothesis tested was that pigments in plants protected grain against the panicle diseases grain mould and head smut. Near‐isogenic tan or purple plant colour genotypes with white grain were planted at Lincoln and Ithaca, NE and Corpus Christi, TX. The field grown grain was plated onto semi‐selective media to detect the presence of grain colonisation by mould genera Alternaria, Fusarium and Curvularia. More Fusarium and Curvularia spp. were recovered from grain grown at Corpus Christi than the Nebraska locations; however, there was no indication that the grain from purple plants was more resistant to the three fungal genera. Most fungi were identified morphologically as Alternaria alternata. Molecular identification of Fusarium species, using translation elongation factor 1‐α gene sequences, showed that Fusarium thapsinum and Fusarium proliferatum infected grain at all three locations. Head smut disease of panicles, caused by the fungus Sporisorium reilianum, was assessed at Corpus Christi; surprisingly, purple plants had significantly greater disease incidence than tan plants. We propose that the tan plant colour lines with white grain are promising for development of food‐grade sorghums not more susceptible than pigmented lines to grain mould and head smut.     

Developing a flexible,high‐efficiency Agrobacterium‐mediated sorghum transformation system with broad application

Sorghum is the fifth most widely planted cereal crop in the world and is commonly cultivated in arid and semi‐arid regions such as Africa. Despite its importance as a food source, sorghum genetic improvement through transgenic approaches has been limited because of an inefficient transformation system. Here, we report a ternary vector (also known as cohabitating vector) system using a recently described pVIR accessory plasmid that facilitates efficient Agrobacterium‐mediated transformation of sorghum. We report regeneration frequencies ranging from 6% to 29% in Tx430 using different selectable markers and single copy, backbone free ‘quality events’ ranging from 45% to 66% of the total events produced. Furthermore, we successfully applied this ternary system to develop transformation protocols for popular but recalcitrant African varieties including Macia, Malisor 84‐7 and Tegemeo. In addition, we report the use of this technology to develop the first stable CRISPR/Cas9‐mediated gene knockouts in Tx430.     

The Physiology of Heterosis in Sorghum with Respect to Environmental Stress

The hypothesis that heterosis in biomass production of sorghum(Sorghum bicolor L. Moench) may be ascribed to stability incarbon exchange rate (CER) over a wide range of environmentalconditions was evaluated. This hypothesis was based on previousresults from detached leaves that hybrids sustained greaterCER over a wider temperture range than their parents. Two grain sorghum hybrids (ATx378/RTx430 and ATx378/RTx434)and their parental lines were grown in the greenhouse in a gradientof ambient temperatures under two water regimes (well-irrigatedand drought up to heading). Plant water-use (estimated by weighingpots), leaf area, leaf gas exchange, grain yield, and above-groundbiomass were determined. Significant heterosis was found for biomass, grain yield perplant, and grain number per panicle. No heterosis occurred forharvest index, indicating that heterosis in grain yield wasdue to heterosis in biomass. Neither growth duration nor leafarea could explain heterosis in biomass. CER and stomatal conductancefor hybrid ATx378/RTx430 in the controls were greater than forboth its parents at leaf temperatures above 38 °C. This,however, was not observed in the other hybrid which was lessheterotic for biomass and grain yield in the controls. WhenCER data were subjected to a stability analysis by joint linearregression, the two hybrids had greater CER than their respectiveparents especially under conditions favouring high CER. Whenextreme stress conditions developed, the hybrid's performancedepended on its genetic background more than on heterosis. Sorghum, Sorghum bicolor L. Moench., heterosis, hybrids, photosynthesis, transpiration, stomata, drought, heat, temperature     

Effects of level,time, and splitting of urea on the yield of irrigated direct seeded rice

Summary To determine effects of level and time of application of urea on grain yields, components of grain yield, and nitrogen use efficiency by irrigated direct seeded rice (Oryza sativa L. var. IR 298-12-1-1-1), three field experiments were conducted at the Gezira Agricultural Research Station during the period 1976–78. The treatments included the factorial combination of three levels of nitrogen as urea (0,75 and 150 kg N/ha) two or three splits, and three times of topdressing of urea (early season application, 10 days after rice emergence, DRE; maximum tillering stage, 40 DRE; and panicle initiation stage, 75 DRE).Without application of nitrogen, grain yields averaged 1.5 t/ha. The yields averaged for rate and time of split significantly increased with increase in nitrogen applied to 3.9 and 5.0 t/ha, but nitrogen use efficiency (kg rice/kg N) decreased from 31 to 23 with the application of 75 and 150 kg N/ha respectively.As compared to other treatments of time of urea application, topdressing of urea at maximum tillering and panicle initiation stages significantly improved nitrogen use efficiency by promoting production of more panicles per unit land area, and increasing grain weight. Three splits were no better than the two splits given at maximum tillering and panicle initiation stages.