Chilean Journal of Agricultural Research

ABSTRACT Mungbean (Vigna radiata (L.) R. Wilczek var. radiata) yield is dramatically constrained by powdery mildew (PM) caused by Sphaerotheca phaseoli (Z.Y. Zhao) U. Braun (1985), which is considerably prevalent in the cool-dry season of production in South, East, and Southeast Asia countries including Thailand. Exploitation of varieties resistant to the disease is crucial to meet sustainable production. A population of 64 F2:9 and F2:10 recombinant inbred lines (RILs) generated by hybridization of the susceptible parent ‘Chai Nat 72’ (CN72) with the resistant parent ‘V4758’ was used to assess genetic resistance and identify inter simple sequence repeat-anchored resistance gene analog (ISSR-RGA) markers linked to the PM resistance gene. The PM response in these RILs was visually scored in the field during the winter seasons, twice in 2015 and 2018, and the segregation pattern was determined by the chi-square test (χ2). The resulting segregation ratios of 1:1 indicated a qualitative nature with a dominantly inherited resistance gene conferring PM resistance. When bulk segregant analysis (BSA) was undertaken using 378 ISSR-RGA primer combinations among both parents and DNA bulks of resistant and susceptible F2:9 individuals, 11 of these exhibited polymorphisms, and one marker I41tP379 was closest to the PM resistance gene which revealed a highly significant correlation with PM resistance (R2 (%) = 26; P < 0.001) with a logarithm of odd (LOD) score of 5.85. The closest marker I41tP379 could trace the PM resistance gene in molecular marker assisted breeding for mungbean improvement.

ABSTRACT Drought and temperature stresses are known as primary factors limiting germination and seedling growth. Seed priming with plant growth regulators is one of the popular approaches to minimize adverse environmental stresses. This study was carried out to examine the role of seed priming with 5-aminolevulinic acid (5-ALA) at different levels (0, 25, 50, and 100 mg L-1) in germination and seedling growth of three wheat (Triticum aestivum L.) ‘Emam’, ‘Gomria’, and ‘Zakia’ under high temperature and drought stresses using a range of temperatures (25, 30, and 35 ℃) and water potentials (0.0 and -0.5 MPa). Water uptake, germination and early seedling growth attributes were measured. Drought stress and high temperature decreased germination%, germination index, and shoot fresh weight by 39.2%, 35.4%, and 48.6%, respectively, as compared with 0.0 MPa and 25 ℃. Seeds of ‘Zakia’ primed with 50 mg L-1 5-ALA at -0.5 MPa, and 35 ℃ increased fresh and dry weights of the root by 19.8% and 68.4% relative to 0 mg L-1. For interaction between variety and 5-ALA, the highest germination% (90.3%) was recorded in ‘Emam’ with 50 mg L-1 5-ALA. Treatment 100 mg L-1 5-ALA decreased mean germination time by 24.5% and 28.9% at 25 and 35 ℃, respectively; 50 mg L-1 5-ALA increased seedling vigor index by 16.3% as compared with 0.0 mg L-1 at -0.5 MPa and 35 ℃. The 5-ALA enhanced water imbibition of the three varieties under drought and temperature stresses. This study suggested that seed priming with 5-ALA is a possible way to mitigate the negative effects produced by drought and temperature stresses on germination and early seedling growth of wheat.

ABSTRACT Intercropping has benefited the global agricultural sector in several ways. It is a critical farming practice for long-term productivity, agro-ecological improvement, land management, and land use. It is a well-known method to increase soil health and crop productivity. The impact of intercropping on the yield and production of maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) has been investigated at the leaf, stem, and root level. However, there is limited information about how to determine the best planting density for maize-soybean intercropping (MSI). The benefits and drawbacks of MSI are discussed in this review. Intercropping maize and soybean improves resource use, lodging resistance, and pest and weed control according to the existing research. Furthermore, soybean has low light use efficiency (LUE) and radiation use efficiency (RUE) due to the deep shade created by the maize canopy. As a result, more research is required to discover the optimal planting density to improve light and radiation efficiency.

ABSTRACT Salinity is a serious threat for global agriculture, especially in arid and semi-arid regions where its incidence leads to considerable damages in the crop growth and production. Carica papaya L. is currently one of the most cultivated fruit crops in the tropical and subtropical areas, and generally, papaya cultivars exhibit a moderate sensitivity to salinity, although such responses may depend on the genotypes. In the present study, papaya seedlings were subjected to salt stress (100 mM NaCl) for 41 d and to exogenous gibberellic acid (GA3; 0.1 mM) and proline (10 mM) pretreatments to evaluate plant physiological variables linked to stress responses. Analysis of the data (P < 0.05) showed a general decrease of plant growth parameters induced by solely salt stress compared to control, such as stem height (47%) and thickness (33%) and plant fresh and dry mass (84% and 83%, respectively), as well as a reduction in the stomatal opening (93%), chlorophylls (40%) and carotenoids (71%) concentration. By contrast, a significant increase was found in foliar and radicular proline levels under stress (87% and 47%). Exogenous foliar GA3 or proline respectively induced a better performance of plants under salt stress by increasing stomatal conductance (444% or 350%), stem height (142% or 144%) and plant biomass (49% or 41%) regarding solely stressed plants, and leading to pigments concentrations close to those from control plants. The results suggest that exogenous gibberellic acid and proline as growth regulator and osmo-regulator solute, respectively could increase papaya seedlings adaption against salt stress.

ABSTRACT The root-knot nematode Meloidogyne spp. causes yield losses of up to 68% on tomato (Solanum lycopersicum L.) crops. Genetic resistance in the host plant makes the crop sustainable and it can breakdown when there is a high population density of the pathogen. The objective of this study was to determine the nematode population density that allow determining the resistance potential of tomato germplasm associated with the Mi-1 resistance gen. The Mi-1 gene was evaluated with the molecular marker SCAR Mi-23 and specific primers in the genotypes COLY007, IAC1687, LA0445, IAC1622 and two commercial controls (susceptible and resistant). The damage scale and the number of individuals recovered (eggs and juveniles) were assessed, with different population densities of the pathogen inoculated (0, 1000, 2000, 3000, 4000 and 5000 individuals plant-1), in a split plot design, with six replicates and a plant as the experimental unit. The genotype IAC1687 and the resistant commercial control presented the resistance allele of the Mi-1 gene and were classified as moderately resistant to a density of 1000 individuals plant-1. Despite having the Mi-1 gene, the COLY007 genotype was classified as moderately susceptible and with densities greater than 1000 individuals plant-1 can break resistance in all genotypes evaluated. Additionally, it is necessary to correlate the genotypic and phenotypic responses to guarantee the success of the selection supported by molecular markers such as SCAR Mi-23 and identify promising genotypes that could be included in a long-term breeding and also used as rootstocks in an integrated management of root-knot nematode.