Research Of Regenerative Plants Induced By Agrobacterium Rhizogenes In Hairy Root Cultures And Drought Resistance In Maize

This paper reports hairy roots induced by Agrobacterium rhizogenes and production ofregenerative plants from hairy root cultures in Maize. The root lines of regenerative plantsgrew rapidly, showing more branching roots and lateral roots. In the dissertation, consideringthe complexity of drought-resistance, comparing to some lines of H99, Jidan 101, and Sidan 8,the morphological, physiological, and developmental characteristics of drought-resistance inregenerative plants of Maize (Zea Mays L.) were systemically studied and compared to. Theindexes systems of drought-resistance identification were established quantitative analyzingwith methods of grey correlation degree, subordinate function values and systematic analysisof clustering. The high drought-resistance on the morphological, developmental, andphysiological characteristics under water stress were showed in strong root lines ofregenerative plants from hairy root cultures in Maize.1. The explants from maize H99 seedlings and embryonic calli were induced by threestrains of virulent A. rhizogenes, R1601, ATCC15834, and A4 in this study. Afteroptimization of the explants, growth condition, Agrobacterium infection process,and hairy roots growth condition, the hairy roots cultured in hormone-free mediashowed the vigorous growth with typical hairy root features. In this study, we foundthat A. rhizogenes (A₄ and ATCC15834) concentration (A₆₀₀=1.0), the time ofsubmerged leaf disks in the bacterial suspension (25 min), long-term co-cultivation(3-d), pH-6.0, 50 u mol/L acetosyring concentration, and medium containingcefotaxime (100 mg/l) and carbenicillin (150 mg/l) for removing bacteria weresuperior for transforming the Ri plasmid in Maize calli only.2. In terms of plant regeneration from hairy roots, different ratios of hormone exhibitedvarying degrees of response. Hairy roots induced by strains ATCC15834 and A4 inmedia No.3 developed into plantlets directly. In contrast, no response at all was inthe control.3. The PCR analysis showed that amplification with the rol C primers showed a 500 bpband for the transformed roots, no band was observed for the untransformed roots.PCR-Southem hybridization further proved that rolC gene were integrated intogenome of hairy roots and regenerated plantlets.4. The growth and physiological activity of the root lines of Maize were inhibited ordecreased at different development stages, such as length, number, volume, dryweight, total absorbing area, and active absorbing area decreased evidently underwater stress. The quantitative analyzing with methods of grey correlation degree showed that the root dry weight, root number, and leaf areas of single plant wasgreatly related to drought-resistance. The height, fresh weight of single plant, dryweight of single plant, leaf areas of single plant, yield of single plant and yieldcomponents were reduced under water stress at different development stages.5. The content of chlorophyll (chlorophyll a and chlorophyll b), photosYnthesis rate,transpiration rate, intercellular CO2 concentrations, and stomatal conductance wasall reduced under water stress at different development stages. The decreased valuesof total chlorophyll were proportional to the decrease of chlorophyll a. Meanwhile,the stomatal conductance was related to the net photosYnthesis rate.6. Under water stress condition, whole root hydraulic conductivity of Maize wasdecreased, the results showed there were different decrease extents at differentMaize lines, such as the regeneration plant was increase by 13.2%, 84.7% H99,34.7% Sidan 8, and 37.4% Jidan 101. The order of decrease extent was H99＞Jidan101＞Sidan 8＞the regeneration plant from hairy root culture in Maize.In short, the indicators of regeneration plants from hairy root culture declined slightlyunder water stress. However, compared to the control lines, varieties will remain at arelatively high level, the difference was significant (p＜0.05). The regenerative plants fromhairy root culture in Maize with high root lines can support its moisture metabolism wellunder water stress during growth and developmental stages. So, the regeneration plantsshowed that there were lower sensitivity Indexes and higher adaptability fordrought-resistance under water stress during its development stages.