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Sclerotinia stem rot is a broad-spectrum threat to rapeseed production, and Brassica juncea contains abundant genetic resources for resistance against Sclerotinia sclerotiorum. Therefore, it is of great significance to carry out screening, localization, and exploration of resistance loci for sclerotinia stem rot in Brassica juncea germplasm resources for the breeding of Sclerotinia-resistant rapeseed. In this study, the S. sclerotiorum resistance of Brassica juncea germplasm resources collected from various regions in Yunnan Province was evaluated under three different growth environments, and a whole-genome association analysis of S. sclerotiorum resistance loci was conducted based on the resequencing data of 91 Brassica juncea germplasm materials. According to the results of leaf identification under in vitro conditions in the three growth environments, one highly resistant germplasm material J7667 and one relatively resistant germplasm material J047 were selected. The resequencing data of the 91 materials were aligned to the reference genome of Brassica juncea for variation detection analysis, resulting in the detection of 11 337 871 SNPs and 40 170 Indels distributed on the 18 chromosomes of Brassica juncea. After data filtering, 403 211 high-quality SNPs were obtained. The phenotypic data of in vitro leaves, in vitro stems, and stem resistance to S. sclerotiorum of the 91 materials under the three growth environments were subjected to whole-genome association analysis using two analysis software, Emmax and Tassel. In the in vitro leaves, both analysis methods identified a total of 62 significantly associated SNP loci with resistance in the three different growth environments, including 23 and 39 significantly associated SNP loci in the Luoping winter sowing and Xiaoshao winter sowing environments, respectively, while no resistance loci were detected in the Xiaoshao summer sowing environment. In the stem of Luoping winter sowing, both methods detected 3 significantly associated SNP loci with resistance, while no significant SNP was detected in the stem of Xiaoshao summer sowing. In the Tassel method, closely located resistance SNP loci were detected on chromosomes A2, A8, and B2 in Luoping winter sowing and Xiaoshao winter sowing, while in the Emmax method, closely located resistance SNP loci were detected on chromosomes B5 and B8 in Luop-ing winter sowing and Xiaoshao winter sowing. In addition, this study mapped the previously identified S. sclerotio-rum resistance QTL loci and the resistance loci identified in this study to the reference genome of Brassica juncea. It was found that the resistance QTL intervals identified in this study (XLRA2-2, XLRA1-4) overlapped with the reported resistance QTL loci Sll2 and qsr10-1, respectively. [ABSTRACT FROM AUTHOR]

We examined the growth and physiological characteristics of Chlorophytum comosum and Chlorophytum comosum var. variegatum by hydroponics at different Cd 2+ concentrations (0, 20, 80, 200 μmol·L -1 ). The results showed that 20 μmol·L -1 Cd 2+ did not affect those two varieties, with no changes of single leaf area, total leaf area, chlorophyll (Chl) a content, Chl (a+b) content, carotenoid content, Chla/Chlb value, intercellular carbon dioxide concentration ( C i ) and transpiration rate ( T r ) compared with the control (CK). Under the 80 μmol·L -1 Cd 2+ stress, the initial fluorescence ( F o ) and non-photochemical quenching coefficient (NPQ) were the highest for both varieties. As for Cd 2+ at 200 μmol·L -1 , the biomass, chlorophyll content, maximum net photosynthetic rate ( P n ), stomatal conductance ( g s ), maximum photochemical quantum yield ( F v /F m ), actual photochemical quantum yield Y (II) , the transfer factor (TF) of both varieties and all parts biomass decreased to the lowest, while peroxidase (POD), ascorbic acid peroxidase (APX) and catalase (CAT) activities of two varieties and MDA content of C. comosum var. variegatum increased in different degrees. With the increases of Cd 2+ stress, the Cd content in organs of two varieties showed an increasing trend, with higher Cd accumulation in roots. C . comosum had higher Cd content and bioconcentration factor (BCF) in all organs than C . comosum var. variegatum . It suggested that two varieties had the ability to resist Cd stress. The tolerance of C . comosum was stronger, and thus could be considered as a green plant to remediate Cd contaminated water or soil.

In this study, the effects of exogenous abscisic acid (ABA) on the growth and physiolo-gical characteristics of Machilus yunnanensis seedlings were examined under well water supply conditions (70%-75% field capacity, FC) and different drought stress conditions, i.e., light drought stress (50%-55% FC) and severe drought stress (30%-35% FC), respectively. The results showed that drought stress reduced leaf relative water content, plant height, and total biomass of seedlings significantly decreased, as well as net photosynthetic rate and maximal photochemistry efficiency (F v /F m ), but enhanced root/shoot and malondialdehyde contents (MDA). Exogenous ABA improved the adaptability of seedlings under drought stress, especially under severe drought stress, with leaf relative water content being improved 21.0%. Plant height and biomass allocation were improved by exogenous ABA under drought, while root/shoot was improved by 1.1 times compared with the well watered plants. The accumulation of MDA was decreased, the activities of CAT and SOD were significantly increased, and the proline content was increased 6.7 times by exogenous ABA under drought. Exogenous ABA application alleviated the negative effect of drought on photosynthetic organs, reduced the decrease of net photosynthetic rate and stomatal conductance under drought, and enhanced F v /F m value. The results suggested that exogenous ABA treatment could enhance the resistance of M. yunnanensis to drought stress.