Journal Of Crop Protection
Volume:11 Issue: 1, Mar 2022

Fungal plant diseases can severely damage oil palm crops and compromise agricultural yields. To ensure a high crop yield while keeping the fungal pathogens at bay, microbial control to combat such diseases offers a more sustainable alternative to chemical control. It is safer to replace chemical fungicides with eco-friendly bio formulations containing living fungi or bacteria and their products to manage fungal infestations on plants, especially oil palm. This is because natural antagonistic microorganisms/substances form components of biofungicides and protect plants by various modes of action such as hyperparasitism, antibiosis and/or by induction of systemic resistance. Microbial agents’ application in managing fungal plant diseases, especially oil palm crop diseases, promises a safer and sustainable agricultural system to control fungal phytopathogens while ecologically less polluting. This article briefly describes the different bioformulations and the mechanism of action of microbial agents to manage fungal phytopathogens of crops, especially in oil palm. A summary of various merits and demerits of biofungicides over synthetic ones and the future outlooks are also highlighted. Bio-based microbial agents for controlling fungal phytopathogens, especially in oil palm plants, appear to be a promising fungal pest management approach considering the growing need for sustainable practices in the agronomic sector.

Downy mildew is one of the most important diseases of cucurbits in the world and Iran. The development of the disease was investigated in a commercial variety (Sakata® F1 Hybrid Saso), three hybrids and eight pure lines of cucumber, four pure squash lines, and one commercial cultivar of watermelon (Sakata® F1 Charleston Gray 243) in two consecutive years (2017 and 2018 spring and summer) at the experimental field of the University of Guilan, Iran to identify the sources of resistance. Plants were regularly inspected until the downy mildew symptoms appeared. The disease was measured using standard scale and Image J software at five stages in the plant growing season. Comparison of disease progress curves, final severity of the disease, and area under the disease progress curve (AUDPC) showed that cucumber B10 and A12 pure lines were the most susceptible and resistant in both years, respectively. None of the squash lines were infected in the first year, but in the second year, two lines showed the disease symptoms, and the severity of the disease in these lines was close to each other. The commercial cultivar of watermelon was not infected in both years.

Identifying resistant genotypes is necessary to control wheat take-all disease Gaeumannomyces graminis var. tritici. In this study, 30 bread wheat genotypes were evaluated under greenhouse and field conditions. The genotypes were evaluated with fifteen molecular markers (SSR and specific primers for translocation wheat-rye). The genotypes were divided into four groups based on disease severity (the greenhouse) and agronomic traits (the field). Chi-square results showed the interactions for these groupings. The correlation between disease severity and agronomic traits indicated that plant resistance is strongly dependent on plant yield. Based on cluster analysis for molecular data (based on simple matching similarity coefficient and UPGMA method), genotypes were separated into resistant and susceptible ones. The correlation between disease severity and amplified loci showed that disease resistance is interactive with xbarc232, xbarc124, and gpw95001 markers. Resistance to take-all disease is probably associated with the interaction of several genes. These results add significant information to our knowledge of the chromosomal location of genes for the take-all disease.

Cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), is a cosmopolitan polyphagous pest. Researchers need a simple mass rearing procedure to study the life history, behavior, and feeding habits of insects. In the present study, effects of container type (Petri dishes or transparent cubic-containers), the form of positioning the containers (overturned or upright), and diet type (artificial diet or natural diet, i.e., chickpea plants) on the development and survival of neonate of H. armigera were assessed. Additionally, effects of container type and ventilation (air circulation in rearing containers) on development and survival of second to sixth instars, percentage of pupation, and adult emergence were assessed. Container type had no significant effect on the development and survival of the neonates and subsequent instars. More neonates survived to the second instar when reared in the containers held overturned, compared to those held upright. The neonates reared on chickpea plants had a shorter larval development and a higher survival rate than those reared on an artificial diet. The percentage of pupation and adult emergence of second instars reared individually in ventilated containers was higher than that of those reared in unventilated containers. As a food source for neonates, chickpea plants could improve the mass rearing of H. armigera.

Huanglongbing (HLB) is one of the most destructive diseases of citrus worldwide. The disease keeps spreading in several citrus-growing areas of southern Iran. The potential of (GTG)5-rep marker in revealing the genetic diversity of geographic isolates of Candidatus Liberibacter asiaticus was evaluated in the present study. Twenty-one HLB-infected samples collected from the Hormozgan and Sistan and Baluchestan provinces were used in the trial. PCR with the (GTG)5 primer produced 16 scorable bands, of which nearly 100% were polymorphic among or within the populations. The most observed variation resided within (80.56, P < 0.10) and a substantially less (19.44, P < 0.10) between the populations. The isolates were distributed in two main (A and B) clusters, each consisting of several subgroups. Group A included Sistan and Baluchestan and Hormozgan isolates and the group B embraced Hormozgan isolates. Based on pairwise genetic differences, the Haji Abad and Hashtbandi populations exhibited the highest between-population variation, and the Siahoo, Hashtbandi, Nikshahr, Haji Abad, and Sarbaz showed the greatest within-population variation. The first three coordinates of the principal coordinate analysis explained more than 72.39% of the variation among or within the populations. The first two coordinates explained 58.20% of band variation in plotting, and the first and third coordinates explained 55.54% of band variation. These results may be inferred that the Hormozgan populations might have diverged from the Sistan populations, or both might have originated separately from an initial or parental population possessing a high genetic diversity.

Prior to this study eight species of Mesopolobus Westwood were recognized from Iran. In this study, one species namely M. aspilus (Walker) is newly recorded. An illustration of the external features of this species is provided. All known species from Iran were reviewed, the key to species and their geographical distribution in Iran is provided.

Intercropping is defined as the simultaneous cultivating of two or more crops together at the same time within a field. It has many advantages like pest population reduction, which increases crop yield. This study compared the impact of additive intercropping kidney bean Phaseolus vulgaris L. with some aromatic plants on Thrips tabaci Lindeman, 1889 population. The treatments included kidney bean sole crop, 100 + 50 kidney bean + coriander Coriander sativum L., 100 + 50 kidney bean + ajwain Carum copticum L., 100 + 50 kidney bean + basil Ocimum basilicum L., and 100 + 50 kidney bean + dill Anethum graveolens L. There were six sampling dates at weekly intervals after onion thrips emergence on the leaves. Kidney and bean leaves were collected on each sampling date, and the number of thrips larvae or adults was recorded. Results showed that the intercropping system significantly influences the onion thrips population. The minimum and maximum thrips per leaf were recorded in kidney bean + basil mixed and kidney bean sole crop treatments (0.208 and 0.540 Thrips/leaf). Moreover, there was a significant negative relationship between the number of thrips and kidney beans yield. The highest yield was recorded in kidney bean + basil treatments (2756 kg/ha). Besides, intercropping increased the Land Equivalent Ratio (LER) of bean monoculture. For instance, all intercropping treatments had higher LER than kidney bean monoculture. Among the intercropping treatments, the kidney bean + basil treatment had the highest LER (1.433). Finally, intercropping kidney beans with some aromatic plants could be an eco-friendly strategy in integrated pest management.

The Sunn pest, Eurygaster integriceps (Puton) (Hem.: Scutelleridae), is an economic pest of wheat that reduces the quantitative and qualitative properties of wheat products. We investigated the effect of E. integriceps feeding on six different wheat cultivars (Ghermez (Red), Noodle, Antanius, Sabalan, Azar 2 (with two types of cultivation), and Sardari) on the protein content in the adult’s gut and fat body and their digestive enzymatic activity. All qualified values of the insect feeding on wheat cultivars differed significantly. The least amount of adult weight and protein content of gut and fat body were observed in the insects fed on Ghermez (Red) cultivar, and the highest amount belonged to the Sardari cultivar. The same results for protein content were obtained from SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Also, the lowest and highest gut α-amylase, pectinase, and protease activities were in Ghermez and Sardari cultivars, respectively. Therefore, it was concluded that the type of wheat cultivar affects the food preference of this insect and, thereby, physiological parameters of the insect gastrointestinal tract. Planting a wheat cultivar like “Ghermez,” which may be resistant, can be a suitable and cost-effective method to decrease the chemicals applied against this pest.

The current study assessed the effects of common herbicides produced by different companies on broadleaved and grass weed control and quantitative traits of irrigated wheat. A two-year experiment (2013-2014 and 2014-2015) was designed as an RCBD with three replications. Experimental treatments included two control treatments (weedy and weed-free) and 15 herbicides produced by three Iranian companies (Ghazal, Golsam-Gorgan, and Gyah) and three international companies (BASF, Nufarm, and Syngenta). The results showed that H13 (bromoxynil + MCPA from BASF tank-mixed with clodinafop propargyl from Golsam Gorgan) and H14 (bromoxynil + MCPA from BASF tank mixed with clodinafop propargyl from Ghazal) treatments in 2014 and H5 (tribenuron methyl from Gyah) and H9 (clodinafop propargyl tank-mixed with tribenuron methyl from Golsam Gorgan) in 2015 almost completely controlled broadleaved and grass weeds. In 2014, H4 (2,4-D + MCPA from Nufarm) and H13 treatments with the averages of 7505 and 7338 kg ha-1 ranked first and second in grain yield, while H9 and H12 (bromoxynil + MCPA from BASF tank-mixed with clodinafop propargyl from Gyah) with the averages of 7966 and 7917 kg ha-1 were known as superior treatments in 2015. Averaged by years, the grain yield was 3185 kg ha-1 at weedy treatment (H17). Although there were no significant differences between herbicides, the grain yield (averaged by years and herbicides) was boosted by 88% compared with the weedy treatment. It was concluded that more rainfall and desirable air temperature positively affected the efficacy of the herbicides.

The current study evaluated Pseudomonas fluorescens VUPf5 and three isolates of Bacillus subtilis (GB32, GB12, and VRU1) for induction of resistance against Cucumber mosaic virus (CMV) in cucumber Cucumis sativus L. (cultivar Sultan) plants. Seed treatment with plant growth-promoting rhizobacteria (PGPR) strains significantly reduced the number of symptomatic plants when CMV was mechanically inoculated. Serological analysis using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) also showed a significant reduction in the CMV accumulation in plants treated with PGPR strains. In every treatment, growth indices, leaf chlorophyll content, leaf carotenoid content, leaf, and root Iron, Zinc, Copper, and Manganese concentration of virus-infected plants were significantly increased. The highest reduction in CMV concentration was observed in plants treated with VRU1. The maximum chlorophyll concentration, leaf Iron, copper, and manganese were observed in plants treated with GB32.
Nevertheless, the highest carotenoid content was measured in the VUPf5 treatment. In the case of growth indices, the best results were obtained by VUPf5 compared to untreated control. In addition, the production of lipase, siderophore, protease, cellulase, HCN, auxin, and phosphate carbonate was determined under in vitro conditions. All four strains were positive for siderophore and auxin production. These results suggest that P. fluorescens and B. subtilis should be further evaluated for their potential to contribute to CMV management under in vivo and in situ conditions.

Plant endophytes deployment at the field level affects the productivity of agricultural products. Savory Satureja khuzestanica Jamzad is a valuable medicinal plant native to Iran. In this study, in order to improve the quantitative and qualitative yield of the plant, the development of a suitable method for inoculation of native fungal endophytes to S. khuzestanica is surveyed. Three fungal endophytes (P.I.S.7, D.2.F.1 and D.1.S.1), isolated from savory plants, were inoculated on S. khuzestanica using four different methods (stem injection, foliar spray, soil drench and adding fungi to the soil in granular form) and their impact on plant's growth and its physiological response was analyzed. All inoculation methods, except adding granular form of fungi to the soil, resulted in endophytic colonization of the savory tissues. However, P.I.S.7 isolate was not established in these plants using any inoculated methods. Extent of fungal colonization showed a significant difference with the inoculation method, such that foliar spray had the highest colonization level, followed by stem injection and root drench. The highest rate of fungal colonization belonged to D.1.S.1. isolate. Spraying leaves and stem injection with endophytic fungi, especially in the case of D.1.S.1, significantly enhanced the morphological and physiological characteristics of host plants and the percentage of essential oil yields in these plants. All in all, using the D.1.S.1 isolate and foliar spray method led to savory plants' improved quantitative and qualitative product.

Take-all is a devastating soil-borne disease of wheat Triticum aestivum L. The disease is caused by the pathogenic fungus Gaeumannomyces tritici, a pathogen distributed worldwide in major wheat production areas that causes severe damage to wheat production. Identification of genotypes with the high nutritional value of seeds can be considered in controlling this disease and in wheat breeding programs. Variation of high molecular weight glutenin subunits (HMW-GS) at the Glu-A1, Glu-B1, and Glu-D1 loci was studied using SDS-PAGE electrophoresis in 15 genotypes of bread wheat. A positive correlation was found between 1000-seed weight and the 5 + 10 allele (r = 0.594), indicating that presence of this allele will increase 1000-seed weight. A simple corresponding analysis was conducted to show the relationship between the take-all index and the genetic diversity of genotypes and the association between the bilateral groupings of individuals based on two criteria (genetic diversity and disease response). The result of stepwise regression showed that glutenin subunit null, 7 + 8, 2*, 7 + 9, 5 + 10 have linkage with resistance to take-all disease. Findings are useful in breeding programs to improve baking quality, develop uniformity and improve heterogeneous genotypes by selecting the best genotypes.