Establishment and evaluation of a peanut association panel and analysis of key nutritional traits

Breeding programs aim to improve the yield and quality of peanut （Arachis hypogaea L.）; using association mapping to identify genetic markers linked to these quantitative traits could facilitate selection efficiency. A peanut association panel was established consisting of 268 lines with extensive phenotypic and genetic variation, meeting the requirements for associa- tion analysis. These lines were grown over 3 years and the key agronomic traits, including protein and oil content were examined. Population structure （Q） analysis showed two subpopulations and clustering analysis was consistent with Q-based membership assignment and closely related to botanical type. Relative Kinship （K） indicated that most of the panel members have no or weak familial related- ness, with 52.78% of lines showing K=o. Linkagedisequilibrium （LD） analysis showed a high level of LD occurs in the panel. Model comparisons indicated false positives can be effectively controlled by taking Q and K into consideration and more false positives were generated by K than Q. A preliminary association analysis using a Q＋ K model found markers significantly associated with oil, protein, oleic acid, and linoleic acid, and identified a set of alleles with positive and negative effects. These results show that this panel is suitable for association analysis, providing a resource for marker-assisted selection for peanut improvement.

Elevated CO2 differentially affects tobacco and rice defense against lepidopteran larvae via the jasmonic acid signaling pathway

Atmospheric CO2 levels are rapidly increasing due to human activities. However, the effects of elevated CO2 （ECO2） on plant defense against insects and the underlying mechanisms remain poorly understood. Here we show that ECO2 increased the photosynthetic rates and the biomass of tobacco and rice plants, and the chewing lepidopteran insects Spodoptera litura and Mythimna separata gained less and more mass on tobacco and rice plants, respectively. Consistently, under ECO2, the levels of jasmonic acid （JA）, the main phytohormone controlling plant defense against these lepidopteran insects, as well as the main defense-related metabolites, were increased and decreased in insectdamaged tobacco and rice plants. Importantly, bioassays and quantification of defense-related metabolites in tobacco and rice silenced in JA biosynthesis and perception indicate that ECO2 changes plant resistance mainly by affecting the JA pathway. We further demonstrate that the defensive metabolites, but not total N or protein, are the main factors contributing to the altered defense levels under ECO2. This study illustrates that ECO2 changes the interplay between plants and insects, and we propose that crops should be studied for their resistance to the major pests under ECO2 to predict the impact of ECO2 on future agroecosystems.