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  • Author or Editor: Chen Wang x
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A pot experiment was performed to investigate the effects of Trichoderma harzianum on the root morphology of Malus hupehensis Rehd. seedlings and their soil environment under replant conditions. The experiment consisted of four treatments: continuously cropped soil (CK1), methyl bromide fumigation (CK2), carrier substrate control (T1), and T. harzianum fertilizer (T2). Plant growth parameters, soil phenolic acid content, abundance of soil microorganisms, and root respiration rate were measured. Compared with CK1, plant height, basal diameter, and fresh weight were 34.58%, 27.55%, and 32.91% greater in T2; 11.35%, 12.10%, and 18.33% greater in T1; and 54.34%, 57.64%, and 45.74% greater in CK2. These metrics were significantly higher in the CK2 treatment than in the other treatments. The second highest values were recorded in the T2 treatment. Differences in root architecture were consistent with differences in biomass. Application of T. harzianum fertilizer was associated with increases of 45.45%, 120.06%, 86.44%, and 268.29% in the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), respectively, and there was little difference between T2 and CK2. The contents of phlorizin and phloretin were 39.39% and 51.70% less in T2, respectively, and 17.85% and 18.14% less in T1, respectively, compared with CK1. Trichoderma harzianum fertilizer increased the abundance of bacteria and actinomycetes while decreasing that of fungi. The gene copy numbers of Fusarium oxysporum and Fusarium moniliforme were 64.30% and 49.35% less, respectively, in the T2 treatment. The fungus population and the gene copy number of Fusarium oxysporum and Fusarium moniliforme was the least in CK2 because of the good sterilization effect. The T. harzianum fertilizer showed satisfactory effects in promoting the root growth of M. hupehensis, increasing the root resistance, decreasing the soil phenolic acid content, and significantly reducing the gene copy number of F. oxysporum and F. moniliforme. In summary, T. harzianum fertilizer is an effective and green alternative for the prevention and control of apple replant disease (ARD).

Open Access

Apple replant disease (ARD) causes enormous economic loss and threatens the survival of apple industry worldwide. Fusarium solani is one of the pathogens that has been proven to cause ARD. Samples were collected at different time periods to investigate the mechanism of defense responses of apple to F. solani infection by monitoring the biomass, reactive oxygen species (ROS), and antioxidant enzyme activities of the apple rootstock ‘M.9T337’. In addition, the abundance of transcription of four pathogenesis-related (PR) proteins involved in antifungal defense was monitored. The results showed that the apple root system was normal and had small brown areas. However, there is a rapid burst of ROS during the early infection stage, and the activities of antioxidant enzymes and transcription of PRs increased during this period. With the extension in infection time, the infected root tissues displayed dark brown necrosis, and the activities of antioxidant enzymes and abundance of transcription of PRs decreased gradually after reaching their peak. Eventually, the plant biomass decreased, and the plant died. In conclusion, the levels of ROS and activities of antioxidant enzymes played an active role during the early stage of resistance of ‘M.9T337’ apples to infection by F. solani. Infection by F. solani can destroy the ROS scavenging system, causing oxidative damage and inhibiting the growth of apple rootstocks.

Open Access

Dendrobium wardianum is a key ornamental plant and a valuable traditional Chinese medicine. This research aimed to find the optimal protocol for in vitro inducement of polyploidy in D. wardianum by treating protocorms with colchicine (an antimitotic agent). The experiment consisted of two series of treatments. For the first treatment, the protocorms were subjected to colchicine concentrations of 25, 75, 125, 250, and 500 μM (weight/volume) for 6, 12, and 24 hours. For the second treatment, protocorms were cultivated in culture medium with colchicine (25, 75, 125, and 250 μM) for 30 days. A total of 18 polyploids were confirmed by chromosome counts and anatomical parameters. Polyploids had broad, dark green leaves with increased stem lengths compared with those of diploids. The optimal protocol for these two methods consisted of soaking in 250 μM of colchicine solution for 12 hours, resulting in inductivity of 26%, and cultivating in 75 μM for 30 days, resulting in a mutation rate of 34%. A comparison of these two protocols showed that the latter one induced more stable polyploids, but that the survival rate was slightly lower. The survival and induced mutation rates of these plants were significantly influenced by the colchicine concentration and exposure time. Higher concentrations for longer periods of time resulted in greater mortality rates and longer-lasting side effects. The protocol involving a solid medium and colchicine is worth considering. It will be intriguing to examine this methodology for the induction of stable polyploids of other orchid species.

Open Access

The objective of the study is to clarify the morphology of floral organs of cytoplasmic male-sterle line of tuber mustard. The orignal material is the intra-specific hybrid of Brassica juncea(L).Czern or Coss × Brassica campestris L. ssp. pakinensis (Lour.) Olsson. The flower of this materile is abnormal, especially with yellow-bud and frutiness(0.03 seed per silque), no nectary was observed. When backcrossed with tuber mustard(BC1, to BC7), these abstracts have been solved. Yellow-bud has disappeared in BC7. 12.4 seeds per silque are obtained when pollinated with maintainer line. The generation of BC3, has 3.5 nectarys in average. ranged from 0 to 8. On the other hand, saccate bulge and papllas and external ovules were exsited in some stamens of sterile plant. The morphology of epidermal cells in saccuate bulge and basal portion of soma stamens in BC1 was similar to that of stamen with normal anthers in fertile plants. Neverthless, a few pollens without outer walls are present on the stamen of male-sterle line.

Free access

Apple replant disease (ARD) has been reported in all major fruit-growing regions of the world and is often caused by biotic factors (pathogen fungi) and abiotic factors (phenolic compounds). Soil chemical fumigation can kill soil pathogenic fungi; however, the traditionally used fumigant methyl bromide has been banned because of its ozone-depleting effects. There is thus a need to identify greener fumigant candidates. We characterized the effects of different fumigants on the replanted soil environment and the growth characteristics of Malus hupehensis Rehd. seedlings. All five experimental treatments [treatment 1 (T1), metham-sodium; treatment 2 (T2), dazomet; treatment 3 (T3), calcium cyanamide; treatment 4 (T4), 1,3-dichloropropene; and treatment 5 (T5), methyl bromide] promoted significantly the biomass, root growth, and root respiration rate of M. hupehensis seedlings and the ammonium nitrogen (NH4 +-N) and nitrate nitrogen (NO3 -N) contents of replanted soil. Metham sodium (T1) and dazomet (T2) had stronger effects compared with 1,3-dichloropropene (T4) and calcium cyanamide (T3). At 172 days after T1, the height, root length, and root respiration rate of Malus hupehensis Rehd. seedlings, and the NH4 +-N and NO3 -N contents of replanted soil increased by 91.64%, 97.67%, 69.78%, 81.98%, and 27.44%, respectively, compared with the control. Thus, dazomet and metham sodium were determined to be the optimal fumigants for use in practical applications.

Open Access