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Maize production and quality are affected by infection with plant pathogens. One of the maize's essential and main diseases is downy mildew caused by Peronosclerospora spp. Downy mildew is a limiting factor in increasing production and can reduce production by 80-100%. It is because the affected plant cannot produce cobs. Pathogens obtain nutrients from the host cell, which can kill the cell and damage the surrounding tissues, resulting in visible downy mildew symptoms. Boron (B) plays a role in forming phloem, increasing the fruit's number, weight, bunch weight, and diameter. The primary function of B at the molecular level is the cross-linking of pectin in the plant cell wall. Ramnogalacturonan II (RG II) is a pectic polysaccharide that contributes to the mechanical strength and properties of the primary wall cross-linked by borate diesters. Phosphorus (P) controls the downsides in the greenhouse and field conditions. This study aims to measure changes in chlorophyll index, P and B uptakes in downy mildew affected plants. The field experiment used a group randomized design with six natural phosphate (FA) application treatments and four groups of borax doses as replicates. The results showed that the downy mildew decreased the chlorophyll index of the leaves at different levels of attack. The results of P concentration according to the position of healthy plant leaves were significantly different due to P treatment. In contrast to concentration B, there is no real difference. P and B uptake results in downy mildew-infested plants showed a significant difference only in P uptake in leaves with 1 FA treatment. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) is one of the staple foodstuffs of the cereal group which has a high percentage of carbohydrates, protein, water, and fats. In 2050, maize is expected to double in demand, however, productivity must be balanced with the support management of diseases and pests of maize. Common maize disease is Downy mildew caused by Peronosclerospora spp., this disease attacks the leaves and seeds with 100% damage. This research aimed to determine the pathogenicity and resistance of Talenta, Pioneer 21, and Tamara maize varieties, by using in vivo leaf insertion and leaf spray methods. Fungal isolates were isolated from threshing conidia from maize leaves in the Sleman area field. Observation of fungal pathogenicity and maize resistance was measured based on symptom scale per two days of test and observation of leaf anatomy 45 days after planting. Calculation of fungal pathogenicity against maize varieties used growth analysis, disease incidence, disease severity, Area Under the Disease Progress Curve (AUDPC), and severity unit per time. The result of this research showed that Talenta was moderately resistant, Pioneer-21 was resistant, and Tamara was susceptible to Downy mildew. Downy mildew pathogenicity rate reached 0,07 units/day. Downy mildew infection reached epidermis tissue through stomata on maize leaves. [ABSTRACT FROM AUTHOR]

Corn, an important crop in Indonesia still has a low productivity, thus many efforts are required to fulfill its national demand. One of the solutions to improve corn yield is by applying biostimulant containing chitosan as an active ingredient. Chitosan has been proved to increase plant growth and resistance against diseases. The objective of this research was to study the effects of several chitosan formulas on the yield and diseases occurance in sweet corn (Zea mays var. Bonanza). The chitosan formulas tested were soluble liquid (SL), wettable powder (WP), nano chitosan (NN), and unformulated chitosan (CH). The experiment was arranged using a randomized block design with three replications. All chitosan formulas were applied by seeds soaking for 20 minutes, followed by foliar spraying on corn plants at three weeks after planting (WAP), with the concentration of 500 ppm (400 L/ha spray volume), every three weeks until 9 WAP. Parameters observed were brix value, weight of corn cobs, weight of corn biomass, and plant diseases including downy leaves, leaf blight and leaf rust. The results showed that NN formula increased the brix value up to 7%, the corn cob weight up to 49% and the biomass weight up to 34% compared to the control; whereas SL formula reduced the incidence of downy mildew by 53% at 3 WAP and leaf blight disease by 51% at 6 WAP. In addition, the incidence of corn leaf rust reduced 59-71% in corn plant subjected to all chitosan formulas. Based on the results, application of chitosan in NN formula was best in increasing yield, while in SL formula was best in reducing the incidence of important corn diseases.

Downy mildew caused by Peronosclerospora maydis is an important disease in the centers of corn cultivation in Java. The aim of this study was to determine the effectiveness of a combination of metalaxyl fungicide and varieties that have a high sustainability of downy mildew caused by P. maydis. The study was conducted in Kediri, East Java, which is an endemic area of downy mildew caused by P. maydis. The Split Plot Design with 3 replications was used in this study. The main plots were 5 corn varieties (1) Bima-3 Bantimurung, (2) Bima-20 URI, (3) Lagaligo, (4) Bima-15 Sayang, and (5) Anoman as a susceptible check. The subplots were 5 levels of seed treatment dose with metalaxyl fungicide (0 g/kg, 2 g/kg, 3 g/kg, 5 g/kg, and 7 g/kg seeds). The combination of resistant varieties with metalaxyl at a dose level of 5 g and 7 g/kg of corn seeds was effective in controlling downy mildew caused by P. maydis. In Bima-3 varieties Bantimurung and Lagaligo showed low infection reactions of 7.7-8.1%, and 10.4–11.2% respectively. In a combination of treatment conditions of susceptible varieties (Anoman) with 2, 3, 5 and 7 g/kg seeds, disease incidence reach 100% or most of the plants die. The lower incidence was also followed by yield, ear length and weight of a 1000 seeds that higher than other treatments. The combination of the use of susceptible variety with 2 g to 7 g/kg of metallaxyl doses was not effective in controlling downy mildew caused by P. maydis.

Potential Proposal for A New Type of Peronosclerospora Sorghi from East Nusa Tenggara Downy mildew of corn caused by Peronosclerospra can cause real economic damage. In Indonesia, it is known that there are three species of Peronosclerospora, namely P. maydis, P. phillippinenis, and P. sorghi. Peronosclerospora maydis is the dominant species found in Indonesia. The three species can be identified from their morphological and molecular characters. However, the results of monitoring by the Kupang Agricultural Quarantine Station during 2016-2019 showed that the morphological characteristics of P. sorghi from NTT are different from the morphology from Java and Sulawesi in terms of the number of sterigmata formed from conidiophores. The number of P. sorghi sterigmata from NTT is less than in other locations. This will lead to a smaller number of conidia produced by P. sorghi from NTT. Based on the molecular analysis, the character of P. sorghi isolate from NTT is in a separated family tree from Java and Sulawesi isolates but is included in one group with P. sorghi isolates from USA. The results of morphological and molecular studies showed further study on host ranges, genetic diversity of the fungal isolates as well as shorgum should be considered in the future. Sorghum as the primary host of P. sorghi has been gathered for the genetic data of sorghum originating from NTT and then comparing to the data from Texas, USA. That information will be contributing to determine the identity of P. sorghi from NTT.