Khairulmazmi Ahmad

Morphological and molecular characterization of Fusarium spp. associated with yellowing disease of black pepper (Piper nigrum L.) in Malaysia

Yellowing disease is one of the most important diseases of black pepper (Piper nigrum L.). To characterize the pathogen(s) responsible for yellowing disease of black pepper in Malaysia, 53 isolates of Fusarium were collected from the roots of diseased black pepper plants and from rhizosphere soils from major growing areas in Sarawak and Johor. A total of 34 isolates of F. solani and 19 isolates of F. proliferatum were obtained and identified based on morphological characteristics and molecular techniques. DNA sequencing of the internal transcribed spacers (ITS1 and ITS2) and 5.8S ribosomal DNA regions was conducted to identify Fusarium species. Nucleotide sequence analysis of the ITS regions revealed that this molecular technique enabled identification of Fusarium at the species level as F.solani and F. proliferatum. In a pathogenicity test on 3-month-old black pepper plants, F. solani was pathogenic, but F. proliferatum was not. On the basis of morphology, DNA sequences and pathogenicity of the fungal isolates from the diseased plants, we showed that yellowing disease on black pepper is caused by F. solani

Enhanced Nutritional Programme: An Innovative Approach to Controlling Plant Diseases in the Tropics

Mineral nutrients are essential for the normal growth and development of both plants and microorganisms and play a crucial role in plant–pathogen interactions, which could be beneficial or detrimental to plant health. Excessive nutrient uptake causes toxicity in plants, so meeting optimal nutrient requirements is very important in the prevention of plant nutrient-deficiency symptoms. In most cases, mineral nutrients represent the primary lines of plant defense against plant pathogens and are directly affected by the plant host, pathogens, and environmental factors. In general, mineral nutrients may affect disease resistance through induced defenses, including by the production of toxins, metabolites, and lignin. The application of an enhanced nutritional programme (ENP) to minimize the deleterious effects of phytopathogens has become a hot topic of discussion around the world. Furthermore, various reports from several countries have shown that the application of mineral nutrients such as calcium (Ca), copper (Cu), and zinc (Zn) in a disease-control programme could enhance crop production and quality, suppress various plant diseases, and promote plant growth. Thus, the aim of this chapter is to discuss conventional disease control methods in the tropics with special reference to major diseases in rice, oil palm, and citrus, as well as limitations on their control. Moreover, the potential application of an ENP as part of a disease control programme in plantation crops in Malaysia is also discussed.

Prospect and Potential of Burkholderia sp. Against Phytophthora capsici Leonian: A Causative Agent for Foot Rot Disease of Black Pepper

Foot rot disease is a very destructive disease in black pepper in Malaysia. It is caused by Phytophthora capsici Leonian, which is a soilborne pathogenic protist (phylum, Oomycota) that infects aerial and subterranean structures of many host plants. This pathogen is a polycyclic, such that multiple cycles of infection and inoculum production occur in a single growing season. It is more prevalent in the tropics because of the favourable environmental conditions. The utilization of plant growth-promoting rhizobacteria (PGPR) as a biological control agent has been successfully implemented in controlling many plant pathogens. Many studies on the exploration of beneficial organisms have been carried out such as Pseudomonas fluorescens, which is one of the best examples used for the control of Fusarium wilt in tomato. Similarly, P. fluorescens is found to be an effective biocontrol agent against the foot rot disease in black pepper. Nowadays there is tremendous novel increase in the species of Burkholderia with either mutualistic or antagonistic interactions in the environment. Burkholderia sp. is an indigenous PGPR capable of producing a large number of commercially important hydrolytic enzymes and bioactive substances that promote plant growth and health; are eco-friendly, biodegradable and specific in their actions; and have a broad spectrum of antimicrobial activity in keeping down the population of phytopathogens, thus playing a great role in promoting sustainable agriculture today. Hence, in this book chapter, the potential applications of Burkholderia sp. to control foot rot disease of black pepper in Malaysia, their control mechanisms, plant growth promotion, commercial potentials and the future prospects as indigenous PGPR were discussed in relation to sustainable agriculture.

Investigation of Phytochemical Components and Bioautography of Garcinia mangostana L. Methanol Leaf Extract

The aim of this work to identify chemical components of Garcinia mangostana leaves and test the antibacterial effect on Pseudomonas syringe pv. tomato and Xanthomonas oryzae pv. oryzae using bioautographic procedure. Phytochemical screening of methanolic extract showed that the leaf extract of G. mangostana rich in alkaloids, Flavonoids, Saponins, Tannins, Phenol, Terpenoids, Anthraquinone and Cardiac glycosides. A simple bioautographic procedure, involving spraying suspensions of the bacteria on thin layer chromatography (TLC) plates developed in solvents of varying polarities was used to detect the number of antibacterial compounds present in the extract. This activity was indicated by white spots against a red background on the TLC plates after spraying with 5% TTC aqueous solution. P. syringae and X. oryzae were inhibited by the most compounds separated on the TLC plates from the extract.