A multiplex reverse transcription polymerase chain reaction (RT-PCR) assay was developed to simultaneously detect bean common mosaic virus (BCMV), bean common mosaic necrotic virus (BCMNV), and bean golden yellow mosaic virus (BGYMV) from common bean leaves dried with silica gel using a single total nucleic acid extraction cetyl trimethyl ammonium bromide (CTAB) method. A mixture of five specific primers was used to amplify three distinct fragments corresponding to 272 bp from the AC1 gene of BGYMV as well as 469 bp and 746 bp from the CP gene of BCMV and BCMNV, respectively. The three viruses were detected in a single plant or in a bulk of five plants. The multiplex RT-PCR was successfully applied to detect these three viruses from 187 field samples collected from 23 municipalities from the states of Guanajuato, Nayarit and Jalisco, Mexico. Rates of single infections were 14/187 (7.5%), 41/187 (21.9%), and 35/187 (18.7%), for BGYMV, BCMV, and BCMNV, respectively; 29/187 (15.5%) samples were co-infected with two of these viruses and 10/187 (5.3%) with the three viruses. This multiplex RT-PCR assay is a simple, rapid, sensitive, and cost-effective method for detecting these viruses in the common bean and can be used for routine molecular diagnosis and epidemiological studies.

Late embryogenesis abundant (LEA) proteins are a large protein family that mainly function in protecting cells from abiotic stress, but these proteins are also involved in regulating plant growth and development. In this study, we performed a functional analysis of LEA13 and LEA30 from Arabidopsis thaliana. The results showed that the expression of both genes increased when plants were subjected to drought-stressed conditions. The insertional lines lea13 and lea30 were identified for each gene, and both had a T-DNA element in the regulatory region, which caused the genes to be downregulated. Moreover, lea13 and lea30 were more sensitive to drought stress due to their higher transpiration and stomatal spacing. Microarray analysis of the lea13 background showed that genes involved in hormone signaling, stomatal development, and abiotic stress responses were misregulated. Our results showed that LEA proteins are involved in drought tolerance and participate in stomatal density.

Viruses are an important disease source for beans. In order to evaluate the impact of virus disease on Phaseolus biodiversity, we determined the identity and distribution of viruses infecting wild and domesticated Phaseolus spp. in the Mesoamerican Center of Domestication (MCD) and the western state of Nayarit, Mexico. We used small RNA sequencing and assembly to identify complete or near-complete sequences of forty-seven genomes belonging to nine viral species of five genera, as well as partial sequences of two putative new endornaviruses and five badnavirus- and pararetrovirus-like sequences. The prevalence of viruses in domesticated beans was significantly higher than in wild beans (97% vs. 19%; p < 0.001), and all samples from domesticated beans were positive for at least one virus species. In contrast, no viruses were detected in 80–83% of the samples from wild beans. The Bean common mosaic virus and Bean common mosaic necrosis virus were the most prevalent viruses in wild and domesticated beans. Nevertheless, Cowpea mild mottle virus, transmitted by the whitefly Bemisia tabaci, has the potential to emerge as an important pathogen because it is both seed-borne and a non-persistently transmitted virus. Our results provide insights into the distribution of viruses in cultivated and wild Phaseolus spp. and will be useful for the identification of emerging viruses and the development of strategies for bean viral disease management in a center of diversity.

The yield of common bean (Phaseolus vulgaris L.) is limited by abiotic stresses such as drought and high temperatures, which frequently occur simultaneously under field conditions. This study examined 100 bean genotypes under three environmental conditions, namely, the rainy season (optimal conditions), full irrigation in the dry season (high-temperature stress), and terminal drought in the dry season (combined stress), via a 10 × 10 triple-lattice design. Agronomic parameters evaluated included days to flowering (DF), days to physiological maturity (DM), plant height (PH), aerial biomass (BIO), grain yield (YLD), and 100-seed weight (100SW). The natural temperature exceeded 35 °C during the reproductive stage of the dry season. Combined stress revealed differential adaptive mechanisms in the tested germplasms, indicating that the response to multiple stresses is more complex than the sum of individual stress responses. The average yield under optimal conditions was 1344 kg/ha, decreasing to 889 kg/ha (66.1%) under irrigation with high temperatures and to 317 kg/ha (23.6%) under terminal drought with high temperatures. Under terminal drought with high temperatures, the number of days to maturity decreased by 5%, and the seed weight decreased by 20%. The G69-33-PT and G-19158 genotypes presented high yields under high-temperature stress, with yields above 1800 kg/ha, suggesting specific physiological mechanisms for tolerance to elevated temperatures. Under combined stress, genotypes G69-Sel25, Pinto Mestizo, and Dalia presented yields above 680 kg/ha, indicating adaptations in terms of water use efficiency and tolerance to high temperature. The identification of genotypes with differential stress tolerance provides valuable genetic resources for breeding programs. The diverse origins of superior germplasms (bred lines, landraces, and commercial cultivars) highlight the importance of exploring various germplasms in the search for sources of abiotic stress tolerance for breeding projects aimed at developing cultivars adapted to climate change scenarios where drought and high temperatures occur simultaneously.

Selection by Genetic Expression Profiles of Desi and Kabuli Chickpea (Cicer arietinum L.) Genotypes Tolerant to High Temperature Stress