Biological Physiological And Biochemical Changes In Different Varieties Of Cotton In Response To The Mealybug Phenacoccus Solenopsis Tinsley (Hemiptera: Pseudococcidae) Damage

Phenacoccus solenopsis Tinsley is a new invasive pest in China. Thismealybug, which can damage a wide host plant, especially causes serious harm toboth transgenic and non-genetically modified cotton. The mealybug can cause thecotton growing slowly, blossom drop, boll shedding and other bad phenomenon byprobing and feeding on cotton. The mealybug also secretes honeydew evoking theplant stooty mold and photosynthesis descent. Main cotton areas are all normalregion of Ph. solenopsis in China. Once the mealybug diffuses, it will make a seriousdamage to the cotton production of our country. The biology research of themealybug especially on different varietal cotton and the physiological mechanismpresently has involving only a little. This discussion made a reseach about thebiological differences of Ph. solenopsis.on different varieties of cotton, setted a lifetable of Ph. solenopsis, and anlyzed the mechanism by physiology and biochemistry.The results were as followings:1. The biological differences, correlation and adaptability analysis of Phenacoccussolenopsis Tinsley damaging different varieties of cottonThe mealybug could finish its life cycle both in transgenic and non-transgeniccotton, the duration of1stinstar nymph was significantly longer than2ndand3rdinstar nymph on6tested cotton varieties. The total nymphal stage of the mealybgwas shortest on CCRI59(15.6d) and longest on CCRI48(17.1d); pre-ovipositionperiod was shortest on CCRI47(13.6d) and longest on XZM (17.9d); however thelongest oviposition period (15.7d) and the highest fecundity (247eggs/♀) was onCCRI41, next was CCRI47(224eggs/♀). CCRI41, where the mealybug had alargest fecundity, lower mortality and longest longevity, and where the value of netreproductive rate (R0), intrinsic rate of increase (rm) and the finite rate of increase (λ)were all largest, was the best variety to the Ph. solenopsis. While, CCRI59where the mealybug had a lowest fecundity, highest mortality, shortest longevity, and lowestvalue of R0, rmand λ, was the most unsuitable variety to the Ph. solenopsis.According to the correlation analysis about the biological differences of Ph.solenopsis Tinsley damaging different varieties of cotton, there existed significantpositive correlation among oviposition period, adult stage and longevity, as well asbetween nymphal stage and3rdinstar period. The correlation analyses between thebiochemical substances and the biological parameter showed that, cotton leaves withhigher solubility sugar content would cut down the mortality and lengthen the pre-oviposition period of the mealybug. But the leaves of cotton with higher gossypolcontent would affect the normol growth and development, cut down the vigor andinhibit the reproduction of Ph. Solenopsis.2. Physiology and metabolism of different varieties of cotton damaged byPhenacoccus solenopsis TinsleyAfter the research about the chlorophyll fluorescence parameters (Fv/Fm andFv/Fo) and defense enzymes (i.e., POD, PPO, CAT, PAL) of the cotton leavesdamaged by Ph. Solenopsis, the result followed. The value of both Fv/Fm and Fv/Fosignificantly decreased. And the all defense enzymes activity rose in some degree.Besides, after the stress of induced by Ph. solenopsis, the decreased degree of Fv/Fmand Fv/Fo were all in the order, CCRI41>CCRI48>CCRI59. In another means, Ph.solenopsis fed seriously on CCRI41and lightly on CCRI59. The POD, PPO, CATand PAL activity of the cotton variety CCRI41all rose comparatively lowly. Toinfor that when Ph. solenopsis fed, the cotton, CCRI41generated less antireversionforce substance, which made Ph. solenopsis had much more adaptation on it and thefeeding amount increase. And it would lead the decreased degree of chlorophyllfluorescence parameters in leaves much larger and the biological parameters of Ph.solenopsis much better on CCRI41.3. Protective enzymes activity of Phenacoccus solenopsis Tinsley damaging differentvarieties of cottonThe protective enzymes (GST, CAT, PO) of the mealybug would rose by a certindegree when Ph. solenopsis damaging3different varieties of cotton. Both themealybug’s detoxifying enzyme (GST）and oxidation enzyme (CAT) in vivo weresignificantly higher than the other two (CCRI41and CCRI48) on the cotton variety CCRI59. To infer that the cotton variery CCRI59produced a higher level of toxicprotein, which making Ph. solenopsis must produce much more detoxifying enzymeand oxidation enzyme for adapting the host environment.