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  • Author or Editor: Cui-Guo Wei x
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To select resistant germplasm resources and understand the growth and physiological responses of kiwifruit (Actinidia sp.) to drought stress, five species, Actinidia macrosperma (Acma), Actinidia longicarpa (Aclo), Actinidia deliciosa (Acde), Actinidia hemsleyana (Ache), and Actinidia valvata (Acva), were assessed under tissue culture conditions. Rootless seedlings of five species were cultured in a medium containing polyethylene glycol [PEG (formula weight 8000)] to induce drought stress (0%, 5%, 10%, 15%, and 20%). After a 30-day culture, three growth indices [fresh weight (FW), plant height (PLH), and leaf number (LN)] and six physiological indices were determined, and the drought damage index (DDI) was determined. The DDIs of five species increased, and three growth indices decreased with increasing PEG concentrations. The following changes were observed under 20% PEG treatment conditions: superoxide dismutase (SOD) activities increased significantly in Acma, Aclo, and Ache specimens; peroxidase (POX) activities remained stable in Acde, Ache, and Acva specimens; and catalase (CAT) activities increased sharply in Acma and Acva. Furthermore, the results indicated that soluble sugar (SS) content increased slightly in Acma, Aclo, Acde, and Ache but it decreased in Acva specimens. Proline (PRO) content increased significantly in Acma and Acva, and malondialdehyde (MDA) contents tended to increase under drought stress in all five species. Principal component analysis (PCA) results indicated that the order of drought tolerance in the five genotypes examined in this study under tissue culture conditions was as follows: Acma > Acva > Acde > Aclo > Ache. Therefore, we concluded that Acma and Acva are more resilient germplasm resources that represent promising kiwifruit-breeding materials. Furthermore, tolerance to drought stress in these species should be further investigated under orchard conditions.

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Accurate estimation of the nutrient requirements of Chinese onion is essential to increase its nutrient utilization efficiency and yield. In this study, the yield and nutrient uptake data were collected from major Chinese onion growing regions during 2001 to 2018, and the relationship between Chinese onion yield and nutrient uptake was evaluated using the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model. The QUEFTS model predicted the linear-parabolic platform curve of the balanced nutrient uptake of Chinese onion and estimated the demand of nitrogen (N), phosphorus (P), and potassium (K) for the potential target yields ranging from 40 t/ha to 120 t/ha. The nutrients required for the target yield increased linearly before reaching 60% to 70% of the potential yield. Nutrient requirements for producing 1 t of Chinese onion were 1.91 kg Nā€“0.28 kg Pā€“1.71 kg K. The corresponding nutrient internal efficiency (IE, yield per unit nutrient uptake) was 524.6 kg/kg, 3585.7 kg/kg, and 584.3 kg/kg for N, P and K, respectively. Subsequently, a nutrition decision-making software, Nutrient Expert (NE), for the Chinese onion was developed based on the improved QUEFTS model. Field verification studies for NE fertilizer recommendation were conducted in multiple Chinese onion growing plots for 2 consecutive years. Results showed that the QUEFTS model can be used to accurately estimate the nutrient requirements for Chinese onion within a defined range of target yield.

Open Access