The effect of soil drenching with 10 µM abscisic acid (ABA) on the physiological responses of two spring wheat (Triticum aestivum L.) cultivars released in different decades was evaluated when subjected to a water deficit at jointing or at booting. Exogenous ABA application increased the ABA concentration in the leaves, reduced the stomatal conductance (gs), slowed the rate of water use, decreased the lethal leaf water potential (ψ) used to measure desiccation tolerance and lowered the soil water content (SWC) at which leaf relative water content (RWC) began to decrease and wilting was observed. Exogenous ABA application also reduced reactive oxygen species (ROS) formation and increased antioxidant enzyme activity, leading to a reduction in the oxidative damage to lipid membranes in both cultivars exposed to water stress at jointing and booting. The decrease in leaf RWC and wilting occurred at lower values of SWC in the recently-released cultivar than in the earlier-released cultivar. The recently-released cultivar also had higher grain yield than the earlier-released cultivar at moderate water stress, but the grain yield in both cultivars was reduced by water stress and by the exogenous ABA treatment. However, exogenous ABA treatment increased transpiration efficiency for grain (TEG) of both cultivars under moderate water stress. These results indicate that ABA played an important role in slowing water use and enhancing the antioxidant defence during soil drying, but this did not result in increased yields under drought stress.

A pot experiment was conducted to investigate the effect of the non-protein amino acid, β-aminobutyric acid (BABA), on the homeostasis between reactive oxygen species (ROS) and antioxidant defence during progressive soil drying, and its relationship with the accumulation of abscisic acid (ABA), water use, grain yield, and desiccation tolerance in two spring wheat (Triticum aestivum L.) cultivars released in different decades and with different yields under drought. Drenching the soil with 100 µM BABA increased drought-induced ABA production, leading to a decrease in the lethal leaf water potential (Ψ) used to measure desiccation tolerance, decreased water use, and increased water use efficiency for grain (WUEG) under moderate water stress. In addition, at severe water stress levels, drenching the soil with BABA reduced ROS production, increased antioxidant enzyme activity, and reduced the oxidative damage to lipid membranes. The data suggest that the addition of BABA triggers ABA accumulation that acts as a non-hydraulic root signal, thereby closing stomata, and reducing water use at moderate stress levels, and also reduces the production of ROS and increases the antioxidant defence enzymes at severe stress levels, thus increasing the desiccation tolerance. However, BABA treatment had no effect on grain yield of wheat when water availability was limited. The results suggest that there are ways of effectively priming the pre-existing defence pathways, in addition to genetic means, to improve the desiccation tolerance and WUEG of wheat.

Parthenocarpy largely depends on the coordinated action of hormones produced in unpollinated ovaries, but can be induced by application of exogenous hormones. We evaluated the effects of gibberellins (GA 4?7 ) and 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) on induction and quality of parthenocarpic fruit in Pyrus pyrifolia Nakai 'Cuiguan' pear. Parthenocarpic fruit with a small core and a high edible ratio were induced by GA 4?7 and/or CPPU. GA 4?7 application induced normally shaped fruit with superior quality and normal size, whereas CPPU treatments resulted in abnormally shaped fruit with a larger size and an extraordinarily expanded calyx tube. Among all GA 4?7 treatments, 500 mg L -1 GA 4?7 induced the highest fruit set (91.88 %) and increased fruit size by 85 % compared with fruit induced by 200 mg L -1 GA 4?7 . In addition, the parthenocarpic fruit induced by GA 4?7 accumulated considerably higher quantities of sucrose and less organic acids than pollinated and CPPU-induced fruit. The potential commercial application of CPPU and GA to pear in place of hand pollination is discussed.

The inheritance of leaf and heading-related traits in Chinese cabbage (Brassica rapa ssp. pekinensis) are poorly understood since only a handful of studies of these traits are available till date. In this study, QTL mapping was done for seven leaf and heading related traits that includes gross weight, number of non-wrapper leaves, head weight, head length, head width, head length/head width ratio, and the number of head-forming leaves in 139 F3 families derived from a cross between two diverse Chinese cabbage lines, '501' with small head and '601' with large head. A total of 27 QTL spread over the nine linkage groups were identified for seven leaf and head-related traits, many of which showed major effects clustered in A2, A4, A6, and A8. The results provided a better understanding of the genetic factors controlling leaf and head-related traits in Chinese cabbage.Additional key words: clustering of QTL, EST-based microsatellite, inheritance, leaf head, QTL mapping, simple sequence repeat (SSR) Hort. Environ. Biotechnol. 52(5):494-501. 2011.

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