ARTIFICIAL FIELD INOCULATION OFBREAD WHEAT ADVANCED LINES WITH TILLETIAINDICA, CAUSAL AGENT OF KARNAL BUNT

The reaction to Tilletiaindica of one thousand and ninety twobread wheat advanced lines were evaluated in the field during the crop season 2016-2017. Sowing in beds with two rows was carried out on November 11 and 24, 2016, using 8 g of seed. Five spikes per line were inoculated by injection with 1 mL of an allantoidsporidial suspension (10,000/mL) during the boot stage, and at maturity the percentage of infection was determined by counting healthy and infected grains. The range of infection in the first date was 0-88.83 with a mean of 31.81%, while in the second date it was 0-82.65% with a mean of 24.44%.The range of infection of the two dates was 0.46-83.71% with a mean of 28.12%.Sixteenlines showed a percentage of infection equal or below 5.0% in both dates, and out of those lines, the following five showed less than 2.5%: two sister lines of MUNAL#1/FRANCOLIN#1*2/3/ATTILA*2/PBW65//MURGA(CMSS12Y00701T-099TOPM-099Y-099M-0SY-13M-0WGY), MUNAL#1/FRANCOLIN#1*2/3/ATTILA*2/PBW65//MURGA (CMSS12Y00701T-099TOPM-099Y-099M-0SY-17M-0WGY), BAJ#1/3/KIRITATI//ATTILA*2/PASTOR*2/4/MUTUS*2/TECUE#1, VILLAJUAREZF2009/6/ATTILA/3*BCN//BAV92/3/PASTOR/4/TACUPETOF2001*2/BRAMBLING/5/PAURAQ, and KACHU/BECARD//WBLL1*2/BRAMBLING/4/FRET2/TUKURU//FRET2/3/MUNAL#1. Lines with the highest percentage of infection were: BABAX/LR42//BABAX*2/3/KUKUNA/4/CROSBILL#1/5/BECARD/6/KSW/SAUAL//SAUAL/7/BABAX/LR42//BABAX*2/3/KUKUNA/4/CROSBILL#1/5/BECARD with 88.83 in the first date,MUU/KBIRD//2*KACHU/KIRITATIwith 84.77 and 82.65%in the first and second date, respectively, and TACUPETOF2001*2/BRAMBLING//WBLL1*2/BRAMBLING/6/WBLL1*2/KURUKU*2/5/REH/HARE//2*BCN/3/CROC_1/AE.SQUARROSA(213)//PGO/4/HUITES/7/BAV92//IRENA/KAUZ/3/HUITES/4/2*ROLF07 with 81.67% in the first date. The average of the three highest levels of infection of the susceptible checkwas99.7%.

Field Inoculation of Arbuscular Mycorrhizal Fungi Improves Fruit Quality and Root Physiological Activity of Citrus

Soil arbuscular mycorrhizal (AM) fungi form a mutualistic symbiosis with plant roots and produce many benefits on host plants under potted conditions, while field inoculation of AM fungi on citrus (a woody plant) has been rarely reported. The present study aimed to analyze the changes in mycorrhizal growth, root vitality, and fruit quality of Citrus reticulata Blanco var. Ponkan mandarin cv. Jinshuigan grafted on Poncirus trifoliata L. after inoculation with a mix of AM fungi (Diversispora versiformis, Funneliformis mosseae, and Rhizophagus intraradices) and single F. mosseae. After the second year of AM fungal inoculations, root mycorrhizal colonization (%), root vitality, hyphal length in soil, and easily extractable glomalin-related soil protein content were significantly increased, while difficult-to-extract glomalin-related soil protein content was decreased. Two mycorrhizal fungal inoculation treatments collectively improved fruit quality parameters such as polar diameter, equatorial diameter, the weight of single fruits, fruit peel, and sarcocarp, coloration value, and soluble solids content. Our study, therefore, suggested that field inoculation with AM fungi improved root physiological activities in terms of mycorrhizal growth and root vitality and thus improved fruit quality. The effect of mixed-AM treatment was more significant than that of F. mosseae alone.

Molecular cytogenetics for a wheat–Aegilops geniculata 3Mg alien addition line with resistance to stripe rust and powdery mildew

Background Aegilops geniculata Roth is closely related to common wheat (Triticum aestivum L.) and is a valuable genetic resource for improvement of wheat. Results In this study, the W19513 line was derived from the BC1F10 progeny of a cross between wheat ‘Chinese Spring’ and Ae. geniculata SY159. Cytological examination showed that W19513 contained 44 chromosomes. Twenty-two bivalents were formed at the first meiotic metaphase I in the pollen mother cellsand the chromosomes were evenly distributed to opposite poles at meiotic anaphase I. Genomic in situ hybridization demonstrated that W19513 carried a pair of alien chromosomes from the M genome. Fluorescence in situ hybridization confirmed detection of variation in chromosomes 4A and 6B. Functional molecular marker analysis using expressed sequence tag–sequence-tagged site and PCR-based landmark unique gene primers revealed that the alien gene belonged to the third homologous group. The marker analysis confirmed that the alien chromosome pair was 3Mg. In addition, to further explore the molecular marker specificity of chromosome 3Mg, based on the specific locus amplified fragment sequencing technique, molecular markers specific for W19513 were developed with efficiencies of up to 47.66%. The W19513 line was inoculated with the physiological race E09 of powdery mildew (Blumeria graminis f. sp. tritici) at the seedling stage and showed moderate resistance. Field inoculation with a mixture of the races CYR31, CYR32, CYR33, and CYR34 of the stripe rust fungus (Puccinia striiformis f. sp. triticii) revealed that the line W19513 showed strong resistance. Conclusions This study provides a foundation for use of the line W19513 in future genetic research and wheat improvement.

Antifungal Activity of Bacillus velezensis CE 100 against Anthracnose Disease (Colletotrichum gloeosporioides) and Growth Promotion of Walnut (Juglans regia L.) Trees

Walnut anthracnose caused by Colletotrichum gloeosporioides is a deleterious disease that severely affects the production of walnut (Juglans regia L.). The aim of this study was to assess the antifungal and growth promotion activities of Bacillus velezensis CE 100 as an alternative to chemical use in walnut production. The crude enzyme from B. velezensis CE 100 exhibited chitinase, protease, and β-l,3-glucanase activity and degraded the cell wall of C. gloeosporioides, causing the inhibition of spore germination and mycelial growth by 99.3% and 33.6% at 100 µL/mL, respectively. The field application of B. velezensis CE 100 culture broth resulted in a 1.3-fold and 6.9-fold decrease in anthracnose disease severity compared to the conventional and control groups, respectively. Moreover, B. velezensis CE 100 produced indole-3-acetic acid (up to 1.4 µg/mL) and exhibited the potential for ammonium production and phosphate solubilization to enhance the availability of essential nutrients. Thus, field inoculation of B. velezensis CE 100 improved walnut root development, increased nutrient uptake, enhanced chlorophyll content, and consequently improved total biomass by 1.5-fold and 2.0-fold compared to the conventional and control groups, respectively. These results demonstrate that B. velezensis CE 100 is an effective biocontrol agent against anthracnose disease and a potential plant growth-promoting bacteria in walnut tree production.

The effects of mycorrhizal colonization on phytophagous insects and their natural enemies in soybean fields

The use of belowground microorganisms in agriculture, with the aim to stimulate plant growth and improve crop yields, has recently gained interest. However, few studies have examined the effects of microorganism inoculation on higher trophic levels in natural conditions. We examined how the diversity of phytophagous insects and their natural enemies responded to the field-inoculation of soybean with a model arbuscular mycorrhizal fungus (AMF), Rhizophagus irregularis, combined with a nitrogen-fixing bacterium, Bradyrhizobium japonicum, and a plant growth-promoting bacterium, Bacillus pumilus. We also investigate if the absence or presence of potassium fertilizer can affect this interaction. We found an increase in the abundance of piercing-sucking insects with the triple inoculant irrespective of potassium treatment, whereas there were no differences among treatments for other insect groups. A decrease in the abundance of the soybean aphid, Aphis glycines, with the double inoculant Rhizophagus + Bradyrhizobium was observed in potassium enriched plots and in the abundance of Empoasca spp. with potassium treatment independent of inoculation type. Although it was not possible to discriminate the mycorrhization realized by inoculum from that of the indigenous AMF in the field, we confirmed global negative effects of overall mycorrhizal colonization on the abundance of phytophagous piercing-sucking insects, phytophagous chewing insects, and the alpha diversity of phytophagous insects. In perspective, the use of AMF/Rhizobacteria inoculants in the field should focus on the identity and performance of strains to better understand their impact on insects.

Molecular Cytogenetics and SLAF-seq-based Specific Molecular Markers for a Wheat–Aegilops geniculata 3M g Alien Addition Line with Resistance to Stripe Rust and Powdery Mildew

Background: Aegilops geniculata Roth is closely related to common wheat (Triticum aestivum L.) and is a valuable genetic resource for improvement of wheat. Results: In this study, the W19513 line was derived from the BC1F10 progeny of a cross between wheat ‘Chinese Spring’ and Ae. geniculata SY159. Cytological examination showed that W19513 contained 44 chromosomes. Twenty-two bivalents were formed at the first meiotic metaphase in the pollen mother cells, and the chromosomes were evenly distributed to opposite poles at meiotic anaphase. Genomic in situ hybridization demonstrated that W19513 carried a pair of alien chromosomes from the M genome. Fluorescence in situ hybridization confirmed detection of variation in chromosomes 4A and 6B. Functional molecular marker analysis using expressed sequence tag–sequence-tagged site and PCR-based landmark unique gene primers revealed that the alien gene belonged to the third homologous group. The marker analysis confirmed that the alien chromosome pair was 3Mg. In addition, to further explore the molecular marker specificity of chromosome 3Mg, based on the specific locus amplified fragment sequencing technique, molecular markers specific for W19513 were developed with efficiencies of up to 47.66%. The W19513 line was inoculated with the physiological race E09 of powdery mildew (Blumeria graminis f. sp. tritici) at the seedling stage and showed moderate resistance. Field inoculation with a mixture of the races CYR31, CYR32, CYR33, and CYR34 of the stripe rust fungus (Puccinia striiformis f. sp. triticii) revealed that the line W19513 showed strong resistance.Conclusions: This study provides a foundation for use of the line W19513 in future genetic research and wheat improvement.

Contamination and translocation of deoxynivalenol and its derivatives associated with Fusarium crown rot of wheat in Northern China

Fusarium crown rot (FCR) is one of the most important wheat diseases in Northern China. The main causal agent of FCR, Fusarium pseudograminearum, can produce mycotoxins such as type B trichothecenes. Therefore, FCR could be an additional source of mycotoxin contamination during wheat production. Field inoculation experiments demonstrated that FCR disease severity strongly impacts the distribution pattern of trichothecenes in different wheat tissues. Mycotoxins were mainly observed in lower internodes and a low amount was detected in the upper parts above the 4th internode. However, high levels of trichothecene accumulation were detected in the upper segments of wheat plants under field conditions, which would threaten the feed production. The variation of mycotoxin content among sampling sites indicated that besides disease severity, other factors like climate, irrigation, and fungicide application may influence the mycotoxin accumulation in wheat. A comprehensive survey of DON and its derivatives in wheat heads with FCR symptoms in natural fields was conducted in 80 sites of seven provinces in Northern China. Much higher levels of mycotoxin were observed than those in inoculation experiments. The mycotoxin content varied greatly among sampling sites, but no significant differences were observed if compared at province level, which indicated that the variation is mainly due to local conditions. Trace amounts of mycotoxin appeared to be translocated to grains, indicating that FCR infection in natural fields poses a relatively small threat to contamination of grains, but a larger amount to plant parts that may be used as animal feed. To our knowledge, this is the first report of trichothecene accumulation in wheat stems, heads, and grains following FCR infection in natural field condition. These investigations provide novel insights into food and feed safety risk caused by FCR in Northern China.

Introgression of Maize Lethal Necrosis Resistance Quantitative Trait Loci Into Susceptible Maize Populations and Validation of the Resistance Under Field Conditions in Naivasha, Kenya

Maize lethal necrosis (MLN), resulting from co-infection by maize chlorotic mottle virus (MCMV) and sugarcane mosaic virus (SCMV) can cause up to 100% yield losses in maize in Africa under serious disease conditions. Maize improvement through conventional backcross (BC) takes many generations but can significantly be shortened when molecular tools are utilized in the breeding process. We used a donor parent (KS23-6) to transfer quantitative trait loci (QTL) for resistance to MLN into nine adapted but MLN susceptible lines. Nurseries were established in Kiboko, Kenya during 2015–2017 seasons and BC3F2 progeny were developed using marker assisted backcrossing (MABC) approach. Six single nucleotide polymorphism (SNP) markers linked to QTL for resistance to MLN were used to genotype 2,400 BC3F2 lines using Kompetitive Allele Specific PCR (KASP) platform. We detected that two of the six QTL had major effects for resistance to MLN under artificial inoculation field conditions in 56 candidate BC3F2 lines. To confirm whether these two QTL are reproducible under different field conditions, the 56 BC3F2 lines including their parents were evaluated in replicated trials for two seasons under artificial MLN inoculations in Naivasha, Kenya in 2018. Strong association of genotype with phenotype was detected. Consequently, 19 superior BC3F2 lines with favorable alleles and showing improved levels of resistance to MLN under artificial field inoculation were identified. These elite lines represent superior genetic resources for improvement of maize hybrids for resistance to MLN. However, 20 BC3F2 lines were fixed for both KASP markers but were susceptible to MLN under field conditions, which could suggest weak linkage between the KASP markers and target genes. The validated two major QTL can be utilized to speed up the breeding process but additional loci need to be identified between the KASP markers and the resistance genes to strengthen the linkage.