사과나무에서 대목은 접수의 수세, 조기결실성, 생산성, 내건성, 내습성 및 내동성 뿐 아니라 재식밀도, 정지전정, 지주체계와 같은 과수원의 전반적인 체계에도 영향을 미친다. 미국 코넬대학교에서는 1960년대 후반부터 진행된 Cornell AgriTech 사과대목 육종프로그램을 통해 화상병과 개식장해에 대해 높은 저항성을 갖추고 있는 대목을 꾸준히 선발해 오고 있다. 활용 가능한 일부 엘리트 Cornell-Geneva 대목은 생산성과 함께 내동성도 기존 M26, M9 대목을 능가하는 것으로 평가되고 있다. 본 연구는 최근에 출시된 G 및 CG 계통의 대목을 우리나라의 보편적인 대목인 M26과 M9와 비교하여 다양한 환경조건에 하에서 생장과 생리적인 측면에서 저항성 또는 환경적응성을 평가하여 새로운 유망 대목을 선발하고자 하는데 있다. 2장에서 4주 동안 반복된 침수는 공시대목 ‘후지’ 접목 사과나무의 생리적 반응, 건물생산 및 나무의 생장을 현저하게 떨어뜨리는 결과를 가져왔다. 침수처리 3주째부터 일부 대목의 사과나무에서 잎이 서서히 시들고 생장이 급격하게 감소하면서 대목 간 내습성의 차이가 드러나기 시작하였다. 28일간의 침수처리와 18일간의 회복기간 동안 나무의 생장과 생리반응을 검토한 결과 M9와 G214가 침수에 가장 취약하였고 다음으로는 G202인 것으로 평가되었다. 반면에 CG4814는 침수에 가장 강하였고 CG5087, G935와 G11은 M26과 비슷한 수준의 내습성을 가진 것으로 평가되었다. 3장에서 한발처리구 나무들은 비교적 단기간의 수분부족을 겪은 상황에서도 생장과 광합성 능력의 급격한 저하가 나타났다. 5주간의 반복적인 수분스트레스는 엽면적과 뿌리 발달 억제를 초래하였고 11일간의 회복기간이 경과한 후 수분관련 생리적 기능에서 대목 간에 차이가 나타났으나 여전히 무처리 수준으로 회복하지는 못하였다. 한발에 노출된 사과나무는 단기적으로는 증산억제를 통하여 수분부족에 적응하지만 장기적으로는 지하부 대비 지상부 생장을 억제하여 증산면적을 줄임으로써 가뭄을 회피하는 것으로 보인다. 공시한 대목 중에는 CG5087이 한발스트레스에 가장 민감하게 반응을 하였고 G202, G214 및 G935는 M26보다 내건성이 우수한 것으로, G11, CG4814는 M9와 비슷한 수준을 보이는 것으로 평가되었다. 4장에서. 공시대목의 휴면심도는 CG5087이 가장 얕아서 1월 상중순에 내재휴면이 타파가 되었고 그와 반대로 M26은 1월 하순 이었고 나머지 G11, G202, G214, G935, CG4814, M9는 1월 중순에 내재휴면이 타파가 되는 것으로 조사되었다. 내재휴면기간 동안 대목을 ?35°C에 2시간 노출시켰을 때 전체적으로 경미하게 동해가 발생되었지만 대목 간에는 G202가 CG4814와 CG5087보다 피해율이 다소 높게 나타났다. 타발적 휴면기간 동안 ?25°C에 2시간 노출시켰을 때 대목들의 동해수준이 심각하지는 않았지만 G202가 상대적으로 M26과 M9에 비하여 피해율이 높았다. 따라서 휴면심도와 휴면기 동해 민감성과는 뚜렷한 상관이 없어 보였다. 3월 8일, 4일간 인위적으로 대목줄기 부위에 탈경화 처리를 하고 -8°C에 노출한 결과 G202가 가장 취약하였고 다음으로는 M9, M26, CG4814, G11이었으며 G935와 CG5087의 피해는 거의 나타나지 않았다. 따라서 내재휴면기 동안 내한성은 CG4814, CG5087 ≥ M26 ≥ G11, G214, G935, M9 ≥ G202 순서로 평가되었고 탈경화 처리 후 내한성은 G935 ≥ G11, G214, CG4814, CG5087, M26, M9 ≥ G202 순으로 볼 수 있었다. 5장에서 역병 (Phytophthora cactorum)에 대해서는 알려진 바와 같이 M9가 타 대목에 비해 비교적 높은 저항성을 나타냈다. G 또는 CG 대목 중에서는 G11만이 M9와 비슷한 수준의 저항성을 보였다. 흰날개무늬병(Rosellinia necatrix)에 대해서는 M9와 M26은 민감도가 비슷하였고 G11과 CG4814가 다소 둔감하였으나 G 및 CG계통 대목 간에는 유의성이 인정될 정도는 아니었다. 흰비단병(Athelia rolfsii)에 대해서는 M9와 M26이 매우 민감하여 접종에 의한 고사율이 각각 80%, 53%로 G 및 CG계통 7% (G935) ~ 25% (CG5087)에 비해 현저하게 높게 나타났다. 사과면충 저항성 시험에서는 G935와 CG4814는 M9나 M26과 같은 수준의 감수성을 보였고 나머지 G 및 CG계통 대목은 내성을 가진 것으로 평가되었다. 결론적으로 침수, 한발, 동해, 토양병 및 사과면충에 대한 내성은 대목에 따라 달리 나타났고 동일한 대목도 평가된 환경에 따라 저항성 발달이 상이하게 나타났다. 그러나 이러한 환경적 요인에 대한 적응성 또는 내성을 종합적으로 평가하였을 때 G935와 CG4814가 기존의 M9나 M26을 대체 할 수 있는 유망한 후보로 평가되었다.
In apple trees, rootstocks affect not only productivity, tree vigor, precocity, and resistance to waterlogging, drought, and cold stress but also all areas of the orchard system, including the tree planting density, training, pruning, the support system, and management practices. In the Cornell AgriTech rootstock breeding program, several rootstocks that are highly productive and resistant to fire blight, root rot, replant disease, and cold stress have been developed since the late 1960s. Specific elite Cornell-Geneva apple rootstocks show high resistance to fire blight and good tolerance to apple replant disease and outperform M26 and M9 standard rootstocks not only for productivity but also for cold temperature tolerance. This study aimed to select rootstock series with high resistance to adverse growth environments in terms of plant growth and physiology, using recently bred rootstocks of G and CG series and compared them with rootstocks of M9 and M26, which are the most widely used in Korea. In Chapter 2, repeated flooding for 4 weeks had a markedly negative impact on the physiological responses, dry matter production, and vertical growth of apple trees grated on different rootstocks. Trees were assessed to have good soil adaptability at the initial stages of soil waterlogging. However, from the third week after flooding treatment, the growth of trees deteriorated drastically, as evidenced by symptoms of slowly withering leaves in some trees, and differences in waterlogging tolerance among the rootstock type began to emerge. Examination of the tree's growth and physiological response during 28 days of flooding treatment and 18 days of recovery showed that trees grafted on M9 rootstock were the most sensitive to flooding, and G214 and G202 trees showed similar sensitivity levels as M9 trees. Conversely, trees grafted on CG4814 rootstock were more resistant to flooding than M26 trees, and CG5087, G935, and G11 trees showed comparable tolerance to waterlogging as M26 trees. In Chapter 3, apple trees in the drought treatment underwent dramatic changes in growth traits and physiological responses after prolonged exposure to extreme soil water deficit. Repeated drought stress for 5 weeks resulted in leaf area and root development inhibition. After 11-day recovery by re-watering, there were differences among trees in the water-related physiological functions, but still did not recover to control level. Trees were believed to have developed a drought avoidance mechanism that rapidly reduced above-ground growth as part of reducing the whole plant transpiration in response to extreme water stress. Therefore, the strategy of increasing the root:shoot biomass ratio is expected to contribute decisively to improving tree survival. Among tested rootstocks, trees grafted on CG5087 tree was the most sensitive to drought stress, Meanwhile, drought tolerance was higher in the G202, G214, and G935 trees relative to the M26 tree, which showed a comparable drought tolerance to the G11, CG4814, and M9 trees. In Chapter 4, when the time taken for the terminal bud-burst to reach 60% was 15 days, it was regarded as dormancy breaking, and CG5087 appeared as the rootstock with the shortest internal dormancy period. Whereas, the internal dormancy of M26 was broken at the end of January, and G11, G202, G214, G935, CG4814 and M9 were in mid-January. The cold injury of the rootstocks by ?35°C treatment during the internal dormancy was not severe. However, G202 showed a relatively higher damage rate than CG4814 and CG5087. At ?25 °C treatment during internal dormancy, there was no significant difference (P > 0.05) in the extent of damage among the rootstock type. Therefore, it was difficult to estimate the direct correlation between dormancy intensity and cold hardiness in mid-winter. As a result of dehardening treatment on rootstock stem artificially for 4 days and then exposing to -8°C, G202 was the most vulnerable, followed by M9, M26, CG4814, and G11, and G935 and CG5087 showed little damage. In conclusion, the cold hardiness during the internal dormancy was evaluated in the order of CG4814, CG5087 ≥ M26 ≥ G11, G214, G935, M9 ≥ G202, and during the imposed dormancy after dehardening was G935 ≥ G11, G214, CG4814, CG5087, M26, M9 ≥ G202. In Chapter 5, as is known for phytophthora rot (Phytophthora cactorum), M9 exhibited relatively high resistance compared with other rootstocks. Among G or CG rootstocks, G11 showed resistance comparable to M9. By contrast, sensitivity toward white root rot (Rosellinia necatrix) disease tended to be slightly higher for the M9 and M26 than the G or CG rootstocks. G11 and CG4814 were somewhat insensitive, but significance was not recognized among the G and CG series. Regarding the susceptibility to southern blight (Athelia rolfsii), M9 and M26 were very sensitive, and the mortality was 80% and 53%, respectively, which was significantly higher than those of G and CG series (G935; 7% ~ CG5087; 25%). The difference in woolly apple aphid [Eriosoma lanigerum (Huasm.)] resistance by rootstock types was noticeable. M9 and M26 showed relatively high susceptibility. Among the promising elite rootstocks, G935 and CG4814 were highly susceptible. In conclusion, the resistance against waterlogging, drought, cold, soil-borne diseases, and woolly apple aphid varied among the rootstocks, and the same rootstock also showed variations of resistance depending on the evaluated environment. However, as a result of comprehensive assessment of adaptability or tolerance to these environmental factors, G935 and CG4814 were evaluated as promising candidates to replace the existing industry-standard M9 or M26.
목차
CHAPTER Ⅰ General introduction and Literature review 21.1. General introduction 21.2. Literature review 61.2.1. Plant physiology in waterlogging conditions 61.2.2. Plant physiology in water deficit conditions 71.2.3. Cold hardiness development of plant 91.2.4. Soil-borne diseases in apple 12CHAPTER Ⅱ Waterlogging tolerance 302.1. Abstract 302.2. Introduction 322.3. Materials and Methods 342.3.1. Plant materials 342.3.2. Irrigation regimes 342.3.3. Plant growth measurement 352.3.4. Statistical analysis 362.4. Results 372.4.1. Leaf water potential 372.4.2. Net photosynthetic rate and stomatal conductance 392.4.3. Vegetative growth 412.4.4. Dry matter production 452.4.5. Defoliation and leaf area 472.5. Discussion 492.6. Literature cited 53CHAPTER Ⅲ Drought tolerance 583.1. Abstract 583.2. Introduction 593.3. Materials and Methods 613.3.1. Plant materials 613.3.2. Irrigation regimes 613.3.3. Measurements 623.3.4. Statistical analysis 633.4. Results 643.4.1. Soil water potential and evapotranspiration 643.4.2. Leaf water potential 673.4.3. Net photosynthetic rate and water use efficiency 693.4.4. Vegetative growth and dry matter 713.5. Discussion 763.5.1. Leaf water potential and evapotranspiration 763.5.2. Photosynthesis and related parameters 773.5.3. Vegetative growth and dry matter 783.6. Literature cited 81CHAPTER Ⅳ Cold hardiness 874.1. Abstract 874.2. Introduction 894.3. Materials and Methods 914.3.1. Cold hardiness during internal dormancy 914.3.2. Cold hardiness during imposed dormancy 944.3.3. Cold hardiness after dehardening treatment 954.3.4. Statistical analysis 974.4. Results 994.4.1. Cold hardiness during internal dormancy 994.4.2. Cold hardiness during imposed dormancy 1024.4.3. Cold hardiness after dehardeniing treatment 1054.5. Discussion 1094.5.1. Cold hardiness during internal dormancy 1094.5.2. Cold hardiness during imposed dormancy 1114.5.3. Cold hardiness after dehardeniing treatment 1124.6. Literature cited 115CHAPTER Ⅴ Resistance to soil-borne diseases and woolly apple aphid 1235.1. Abstract 1235.2. Introduction 1245.3. Materials and Methods 1265.3.1. Inoculation methods 1265.3.2. Measurements 1275.3.3. Statistical analysis 1285.4. Results 1295.4.1. Phytophthora root rot (Phytophthora cactorum) 1295.4.2. White root rot (Rosellinia necatrix) 1305.4.3. Southern Blight (Athelia rolfsii) 1325.4.4. Woolly apple aphid [(Eriosoma lanigerum (Huasm.)] 1345.5. Discussion 1355.5.1. Soil-borne diseases 1355.5.2. Woolly apple aphid [(Eriosoma lanigerum (Huasm.)] 1365.6. Literature cited 138SUMMARY 142국문 초록 145APPENDIX 147