International Journal of Agronomy

Rice blast disease caused by the fungus Pyricularia oryzae is considered as one of the severe diseases, leading to reduce tremendous rice productivity in its cultivated areas of Thailand. Due to the rapid evolution and high genetic diversity of the pathogen, the innate rice resistance (R) genes associated with defense mechanisms are significantly considered as the most important for rice breeding program to create new rice varieties, resistant to blast disease. This study aimed to investigate the rice blast R genes (Pi9, Pib, and Pi-ta) in 98 landrace rice germplasms collected from three different provinces in lower northern Thailand, Phichit (PCT), Phitsanulok (PLK), and Sukhothai (STI) through PCR assay. The results showed that the Pi-ta gene was presented in 29 different varieties, making it the most widespread, whereas the Pi9 and Pib genes were found in 28 and 25 varieties, respectively. The distribution percentage of studied genes in PLK and STI germplasms is higher than in PCT germplasms. Interestingly, only eight landrace rice varieties (varieties no. 46, 47, 48, 51, 66, 76, 81, and 90) collected from PLK and STI germplasms contain all of these three resistance genes. This finding provided the genetic information and diversity of the R genes across landrace rice varieties in the lower north of Thailand. Moreover, these R genes could be useful as genetic resources for rice improvement with resistance to blast disease through breeding program in the future.

Orange is one of the most horticulturally important and widely cultivated Citrus species. Citrus cultivar improvement via conventional breeding strategies is normally impeded by factors related to its reproductive biology. The present study was undertaken to investigate the optimization of growth regulators’ composition of media in in vitro propagation of orange cultivar from nodal segment explants. The nodal segment explants were collected from sweet orange cultivars. The MS medium supplemented with sucrose and different concentrations of growth regulators were used for shoot proliferation and root induction. The optimum compositions of growth regulators in MS medium were assessed. The result indicated that the highest shoot response was recorded for Washington naval orange with maximum shoot proliferation rate (99.75%), shoot number per explant (3.10), shoot length (10.70 cm), leaf number per explants (12.50) after three weeks of culture. In all experiments, no growth was observed for the basal MS medium. Phytohormones combinations of indole-3-acetic acid, IAA (1.2 mg/L), and kinetin (2.0 mg/L) were found to be the best for shoot proliferation. Among the cultivars, significantly, the highest rooting rate (81.25%), root number (4.95), and root length (2.95 cm) were recorded for Washington naval orange cultivar. The least rooting rate (48.45%), root number (3.55), and root length (2.26 cm) were observed from the Valencia cultivar. Significantly, the highest rooting rate (84.90%), root number per microshoot (5.20), and root length (3.05 cm) for MS medium supplemented with 1.5 mg/L 1-naphthalene acetic acid (NAA). The comparison of different concentrations of IAA and NAA on root induction of microshoots from nodal segments of sweet orange cultivars demonstrated NAA as the more effective hormone than IAA.

Declining agricultural productivity has been a challenge worldwide and especially in Sub-Saharan Africa (SSA). Low agricultural productivity has been attributed to factors such as poor farm management practices, soil moisture stress, soil infertility, and soil degradation, among others. The nations in the SSA are prone to insufficient crop yields due to their inadequate capacity to adapt to good agricultural practices that support crop productivity such as integrated soil fertility and water management (ISFWM) practices. This lowers the farmers’ capacity to improve crop productivity, thus contributing in jeopardizing the food and nutritional security in SSA. Past research has shown that ISFWM strategies have not been properly adopted probably due to the lack of adequate awareness among the farmers about them. In addition, there is limited documentation on the importance of ISFWM in enhancement of soil fertility, water use efficiency, and sustainable crop production in SSA. This paper discusses some of the key ISFWM options that have the potential to enhance soil fertility, improve water use efficiency, and consequently increase agricultural productivity. The practices include intercropping, use of tied ridges, minimum tillage, mulching, and combined use of organic and inorganic fertilizers.

Arabica coffee is a perennial cash crop and highly affected by biennial bearing which disturbs farmers’ annual income and world’s coffee industries. Developing nonbiennial bearing variety is prominent in addition to applying field management practices. This study was conducted from 2012 to 2020 in southwestern Ethiopia at Tepi and Gera to test the extent of genetic variability among Arabic coffee germplasm in biennial bearing and understand the influences of bienniality on advanced selection. The pooled analysis of variance revealed handiness of genetic variability in yield and biennial bearing. The moderate genotypic coefficient of variation (10–20%), heritability (30–50%), and high genetic advance as percentage of the mean (>20%) were manifested in yield and biennial bearing. Response to selection and selection efficiency were negatively affected by biennial bearing. Early selection excluded 30–40% of the top high yielders from advanced selection. Selection at four harvesting seasons revealed 90% and more selection efficiency. Thus, one has to be conscious of the alternate bearing nature of lines during advanced selection. Both T43/11 and T51/11 were among the top high yielders and showed low biennial bearing at Gera and Tepi. T33/11, T49/11, T55/11, and T61/11 showed very low biennial bearing at both locations. These are promising lines and could be recommended for further biennial bearing improvement breeding programs.

Andrographis paniculata is used in Thai traditional medicine. This plant contains a bitter compound called andrographolide, which is highly effective in the prevention of many diseases. It is an effective treatment for infectious diseases and has a prophylactic effect owing to its powerful immunity-boosting benefits. Recently, it has been widely used to treat COVID-19. However, commercial planting of A. paniculata is performed by seeding, which leads to seed germination problems. The seed germination is relatively low and not efficient under normal conditions for various reasons, such as a combined dormancy of physical and innate nature, the diversity of the seeds in different lots, and the fact that the germination duration was not uniform in the same lot. An easily applied and inexpensive method for farmers to develop mass plantings to stimulate germination is by using macrobubble conditions by aerating seeds in sterile water in collaboration with chemical scarification, which is the idea of creating a hard seed coat that causes seed dormancy to break while root germination occurs at 25°C. Germination was completed after 16 days. The dissolved oxygen (DO) concentrations in this environment were 5, 6, 7, 8, and 9 mg·L⁻¹. The oxygen intensity of 9 mg·L⁻¹ showed the highest germination percentage (26.33%). It was found to be optimal for macrobubble conditions. Seedlings were treated with chemicals (PEG, NaCl, H₂SO₄, KCl, KNO₃, NaHClO₃, and GA₃) after soaking in macrobubbles with optimum DO. The results showed that NaHClO₃ conc. (30 min) showed a generation percentage reaching 92%, which could greatly promote up to 3.63 folds compared with the control in the macrobubble aeration system.

Carrot production is expensive since approximately 51% of the total costs are allocated to the nutrition of the crop. Bacterial inoculants are a promising alternative for crop fertilization. This research aimed to evaluate the effect of Gluconacetobacter diazotrophicus on the performance of carrot cultivar “Royal Chantenay” and its interaction with nitrogen and phosphorus fertilization. An experimental design of sub-subdivided plots was applied, where the largest plot consisted of the reference strain (ATCC 49037) and a native Colombian isolate of the bacterium (GIBI029); two concentrations of the bacterium were applied in the subplots (8.8 × 10⁷ and 18 × 10⁷ CFU/mL), and the levels of nitrogen and phosphorus were sorted within each one of them. The best positive effect was observed with the application of G. diazotrophicus ATCC49037 and GIBI029 at a concentration of 18 × 10⁷ CFU/mL without the application of phosphorus or nitrogen in which yields of 37,417 and 30,606 kg/ha were obtained, respectively, exceeding the national average production in Colombia. In contrast, conventional treatment had a yield of 27,909 kg/ha. Additionally, higher quality was evidenced in the product weight with values of 126.48 g (ATCC49037) and 104.98 g (GIBI029), compared with the conventional treatment (93.19 g). G. diazotrophicus was shown to exhibit growth-promoting properties not only in crops such as sugarcane but also in economically important vegetable crops. The results obtained may contribute to the development of a novel microbial inoculant for vegetables under agroecological conditions in tropical areas.