Resistance Responses of 35 Watermelon Genotypes to Three Isolates of Fusarium oxysporum f. sp. niveum

Fusarium wilt caused by Fusarium oxysporum f. sp. niveum (Fon) is one of main diseases of watermelon. There have been very limited studies that tested watermelon genotypes to more than one isolates of Fon in Indonesia. This research aimed to determine the resistance of 35 watermelon genotypes to three Fon isolates taken from three different areas in Indonesia. Incubation period (IP) and disease index (DI) of the 35 watermelon genotypes were determined against three Fon isolates collected from Karawang (FK), Lampung (FL), and Purwakarta (FP). The experiment was arranged using a Completely Randomized Design with two replications. DI showed that six watermelon genotypes, i.e. New Hope, Sky Mountain, Southern Light, Super Sweet 66, Uranus, and Yellow Baby demonstrated moderate resistance to resistance phenotypes to all tested Fon isolates. IP and percentage of symptomatic plants (PSP) showed different responses among genotypes either to the same or to different isolates. Genotype New Orchid, for example, showed 57.14% symptomatic plants in less than 10 days after inoculation (DAI) when tested with FL isolate. Meanwhile, when tested with the same isolate, genotype New Dragon showed only 6.67% symptomatic plants in more than 23 DAI. The result of this study indicated that watermelon genotypes showing resistant to all tested isolates should be useful for breeding program to develop watermelon lines with broader resistance spectrum against Fon pathogen. The resistance genotypes selected should also demonstrate good agronomic performances and high yield to be considered as a new watermelon variety

Resistance Analysis of CRISPR/Cas9 Genome-Edited Chili M2 Mutant Lines against Pepper Yellow Leaf Curl Viral Disease

Pepper yellow leaf curl virus (PepYLCV) infection transmitted by silverleaf whitefly (Bemisia tabaci [Gennadius]) can decrease chili pepper yield up to 100%. At this moment, there is no chili pepper variety resistant to PepYLCV available. Genome editing approach through CRISPR/Cas9 is an effort to develop variety resistance to the viral infection. The purpose of this study was to obtain M2 lines developed by CRISPR/Cas9 system on proliferating cell nuclear antigen (PCNA) gene for resistance to PepYLCV. A total of four M2 lines (C47-7, L84-2, L84-23, and L120-19) consisting of 60 chili plants were tested for their resistance to PepYLCV. PCR analysis was performed to detect the presence (infection) of the virus. The results showed that a total of 35 plants derived from the four lines were resistant to PepYLCV. They consisted of 7 plants from C47-7 line, 11 plants from L84-2 line, 9 plants from L84-23 line, and 8 plants from L120-19 line. PCR analysis confirmed that the resistant plants obtained from this study were negatively infected by the virus. Since not all tested plants were resistant to virus infection, the PCNA gene allele in these resistant lines were most likely heterozigotes. Sequencing of PCNA gene of the resistant lines is needed to confirm that the resistance phenotypes obtained was due to mutation of the gene. Therefore, further selection needs to be performed to obtain stable and PepYLCV-resistant lines

Utilization of Molecular Markers for Rice Breeding

Rice is the staple food for more than half of the world's population. Rice production in 2050 must increase by at least 50% to keep up with the population growth. Efforts to increase rice production continue using various strategies. Breeders apply multiple approaches including application of molecular markers in developing varieties better than the previous ones. Since the discovery of the restriction fragment length polymorphism (RFLP) markers in 1980s and the development of polymerase chain reaction (PCR) method, many types of molecular markers have been developed and applied to various crops including rice. Various molecular approaches to map genetic loci associated with rice superior traits were conducted. The mapped loci are very useful for rice breeding purposes. This paper reports the results of mapping and breeding economically important traits in rice, mainly those related to abiotic stresses, agronomic traits, yield, and yield quality. These included characters of semidwarf stature, aromatic grain, high yield potential, eating quality, higher Zn and Fe grain, more tolerant to abiotic stresses, such as salinity, drought, phosphate deficiency, Al toxicity and Fe toxicity, submergence, as well as early maturity character. The mapped characters can be transferred using marker-assisted backcrossing (MABC) method into cultivated rice genotypes well-adopted by farmers. Several countries including Indonesia have benefited from this breeding method, and Indonesia have released several rice varieties developed through MABC. These include rice varieties such as Code, Angke, Inpari 30, Inpari Blas, Inpari HDB, Bio Patenggang Agritan, and Bioni 63 Ciherang Agrita

Improving Cassava Productivity by Soil Bioaugmentation with Phosphate-Solubilizing Actinomycetes and Fungi

Cassava is one of the most important food commodities, but its cultivation technique must be improved, especially the technology in increasing soil fertility. Lack of phosphate (P), one of the major biological nutrients in soil, can reduce agricultural production. Some P-solubilizing microbes can play an important role in increasing the availability of P for plants. The purpose of this study was to evaluate the ability of P-solubilizing microbes isolated from cassava rhizosphere in improving the growth of cassava after soil bioaugmentation with the formula of selected microbes. A total of 50 isolates were successfully isolated from cassava plant rhizosphere collected from several locations in South Sulawesi. In vitro screening on Pikovskaya agar media resulted in six Actinomycetes and six fungal isolates with the best P hydrolysis capacity. One Actinomycetes isolate (Streptomyces sp. A-SDR01) and one fungal isolate (Penicillium sp. F-SKG17) with nonantagonistic effect to each other based on in vitro test were able to improve the vegetative growth of cassava under in planta test. Combination of both isolates in a gum arabic formulation increased plant height and productivity compared to untreated plants when applied as soil bioaugmentation in limited field trials at four locations in South Sulawesi. Therefore, application of P-solubilizing microbes that possess soil bioaugmentation properties is recommended for increasing the growth of cassava plants and their use as microbial biofertilizers should be extended to wider areas

Identification of the Pathogen Causing Stem Blight Disease on Chili in Sindangjaya Village, Cipanas, Cianjur, West Java Based on Morphological and Molecular Analyses

Chili (Capsicum annuum L.) is a vegetable commodity with high economic value which is widely cultivated by farmers in Indonesia. One of the obstacles faced in chili cultivation is stem rot disease. This study aimed to identify the pathogens that caused stem rot in chili plants obtained from one location in Sindangjaya Village, Cipanas District, Cianjur Regency, West Java Province based on morphological and molecular analyses. Pathogen identification was performed with morphological and molecular approaches. The morphological characters observed included colony shape, sporangium diameter, and mating type. The pathogenicity of the isolates was assayed by inoculating chili stems aged 40 days. Molecular identification was carried out using two pairs of primers for ITS regions and TEF-1 gene. Based on the results of morphological and molecular identification, as well as pathogenicity tests, it was confirmed that Phytophthora capsici pathogen was the causal agent of stem rot in chili plants collected from Sindangjaya Village. Further study is needed to determine the spread of the disease, damage, and yield loss caused by stem rot disease, as well as how to prevent and control the disease

Genotypic Analysis of Two Local Swamp Rice Based on Microsatellite Markers

Argo is a local swamp rice from Kalimantan which is widely cultivated by local farmers. Exploration activities in Kalimantan found two types of local rice named Argo but demonstrated different phenotypes. Therefore, genotypic verification is needed to determine the differences between the two Argo rice genotypes. DNA fingerprint could help genotype verification rapidly and the result is not influenced by environmental factors. The aims of this study were to determine the level of similarity of Argo-1 and Argo-2 with swamp rice and other irrigated rice genotypes using microsatellite markers. A total of eight improved and local varieties were used as genetic material with the two local rice Argo (Argo-1 and Argo-2). The rice genotypes were analyzed by using eight microsatellite markers. The results of the molecular analysis showed that the two types of Argo showed different DNA bands based on the RM228 marker but genetically they were closely related. The genetic distance between the two Argo cultivars is 0.143. Argo-1 and Argo-2 were located in the same cluster as Inpara 4 and Siam KDK, but they were in the different groups from those of irrigated rice varieties such as Mekongga and Inpari 9. Based on this research, Argo-1 and Argo-2 are not recommended to be crossed with Inpara 4 and Siam KDK because the genetic diversity formed will be narrow

Exploration of IAA and HCN Producing Rhizobacteria from Cassava (Manihot esculenta Crantz) Rhizosphere

Plant growth promoting rhizobacteria (PGPR) are a group of beneficial bacteria that live in rhizosphere. These bacteria can promote plant growth through several mechanisms, such as the ones produce indole-3-acetic acid (IAA) hormone and hydrogen cyanide (HCN), and act as biocontrol agents. The use of PGPR to promote plant growth has been known to be an environmentally friendly alternative approach. The aim of this study was to explore IAA and HCN producing rhizobacteria from cassava rhizosphere soil and identify the bacteria based on morphological and biochemical characters, hypersensitive reaction test, and the ability test to produce IAA and HCN. The results showed nine bacterial isolates suspected as Micrococcus sp. (six isolates), Neisseria sp. (two isolates), and Bacillus sp. (one isolate). All isolates were able to produce IAA in the concentration range of 50,63–135,00 µg/ml and 232,3–333,9 µg/ml at incubation time of 2 and 4 days, respectively. All isolates were able to produce HCN. In addition, the isolates did not show hypersensitivity reactions. Further study is needed to assess the isolate application for promoting plant growth as well as a biocontrol agent of plant pathogen