落花生莢果黑斑病之抗病性及其遺傳研究

Abstract

由於台灣落花生莢果黑斑病，在主要產區雲林縣有漸漸嚴重之趨勢，而一般認為此病害是由複雜的土壤病原菌所引起，主要有 Pythium myriotylum, Rhizoctonia solani, Sclerotium rolfsii及Fusarium solani等，為能減輕此病害之發生，探討主要病原菌及育成抗病品種為重要的方法。因此本試驗目的在探求主要病原菌、篩選抗病品系及對主要病原菌之抗病遺傳行為研究。結果摘要如下： 1. 分析雲林縣元長鄉、崙背鄉、虎尾鎮及本所試驗田等不同感病區落花生莢果之病原菌及土壤成分，結果病原菌之分離率因地點而不同，主要以F. solani及P. myriotylum兩者較重要，尤其春作以P. myriotylum較重要。莢果黑斑病地區間有差異，土壤成分亦有差異，病害因環境及品種不同而不同，且兩者具有交感作用。土壤中Fusarium spp.族群密度一般均高(2×103~10×103)，且以感病田較高，不同生育期其族群密度亦有變化，但與莢果黑斑病、pH值無相關性，而Pythium spp.常偵測不到。土壤Ca含量及pH值高者，其莢果黑斑病較輕，但其相關性未達顯著，其他成分也無顯著相關性。 2. 利用本所保存的種原及引進國外抗病品種，在雲林縣元長鄉之感病試區進行抗病篩選，經過兩年半的抗莢果黑斑病篩選，顯示絕大部分的種原均感病，型態間平均以Spanish type罹病度較低，但差異不大；篩選獲得較抗病品系(<20%)共5個，其中4個屬於Valencia (VA111、VA114、VA220、VA221)，1個為Virginia bunch(VB186)，均來自於美洲，顯示美洲為重要的抗病品系來源，而Valencia型有較抗病的品系。 3. 為瞭解抗病品系之抗病特性，利用田間連續栽培，探討品系對期作之反應，結果品種(系)極容易受年度及期作等環境之影響，二個抗病品系 (VA221及VB186)表現較穩定；期作對莢果黑斑病並無一定相關性趨勢，顯示春、秋作影響程度類似。調查株高、節間長、子房柄長、落葉率、銹病、葉斑病、倒伏、莢殼厚度及產量等10性狀與莢果黑斑病之相關，結果在秋作性狀間均不呈顯著相關性，只在春作莢果黑斑病與葉斑病呈正相關，與產量呈負相關。 4. 為了進一步確定田間抗病品系的抗病性，以不同抗病品系在盆栽接種各種主要病原菌，及施以鈣肥與有機質肥探討對莢果黑斑病的影響，結果病害與品種、病原菌間均有交感效應，會因品種不同或病原菌不同而有變化。一般而言肥料非影響病害之因素，病原菌才是主要因素，但品種x病原菌、肥料x病原菌、品種x肥料x病原菌具有極顯著交感作用，顯示病原菌之接種效果極容易受肥料及品種之影響。抗病品系VB186仍然表現較抗病，病原菌則以p. myriotylum引起之病害最嚴重。 5. 由於病原菌間關係複雜，為了探討病原菌間的相互關係，並希望能找出較重要的一種病原菌，以作為育種及防治上之參考。分別將四種病原菌進行各種混合方式接種(因為參試品種(系)均對白絹病無抗病性，造成枯萎死亡，因此未計入)。結果品種及病原菌處理均有差異，抗病品系VB186平均罹病度最輕，P. myriotylum單獨接種病害最嚴重，而且品種與病原菌處理具有極顯著交感作用，將品種分別進行病原菌處理劃分變方分析，結果不同品種之主要為害病菌不同，栽培種TP11主要受P. myriotylum侵害，其均方值佔約80%；抗病品系VB186也是以P. myriotylum較重要；最感病品系VA179則有三種處理較重要，分別為P. myriotylum、F. solani + P. myriotylum、及R. solani。因為不同品種對於不同病原菌處理有不同之反應，很難判定病原菌間之交互作用，但以P. myriotylum為最重要病原菌。 6. 因很少品種能抗多種病害，而且不同病害其抗病機制可能不同，因此分別在溫室接種主要病原菌P. myriotylum及田間自然發病下，以全互交法及世代平均法分析抗病性之遺傳。結果在Hayman全互交法分析中，抗病性不論溫室或田間，均具有母本效應及正反交效應。莢果黑斑病的抗病性在溫室及田間均為累加性及顯性作用的結果，但溫室及田間有差異，溫室以累加性效應較重要，而田間以顯性效應較重要，在溫室的抗病性為部分顯性，而田間為超顯性。溫室為微效基因控制，田間至少有一對顯性基因控制。溫室遺傳率較高，田間遺傳率較低。在溫室抗病基因多數是顯性，在田間則多數為隱性。組合力分析結果，不論溫室或田間，其莢果黑斑病的抗病性均以累加性基因較重要，而且有正反交效應。兩個抗病品系VA221及VB186的一般組合力均為負值，為良好的育種材料；但兩個抗病品系的一般組合力有差異，顯示二個品系之抗病機制不同，以VB186較強的抗病性。由世代平均值分析結果，抗病基因具有上位性，二個雜交組合之基因交感效應不同。

Summary Pod rot of peanut (Arachis hypogaea L.) occurs in many peanut growing regions in Taiwan. This disease can be caused by an array of soilborne microbes, usually considered to be of complex etiology. Pod rot can also be caused by one of several fungal pathogens acting along or in combination. Fungi that have been reported to cause pod rot are Pythium myriotylum Drechs., Rhzoctonia solani Kuhn, Fusarium solani (Mart.) Appel. & Wr., and Sclerotium rolfsii Sacc.. The purpose of this research was to evaluate the current status of pod rot main pathogen on peanut grown in Taiwan, and screening germplasm and genetics studies for pod rot resistance in peanut. The results obtained are summarized as follows: 1. The prevalence of various pod rot pathogens differs among production regions, farms, and even from crops within a given location. The F. solani was commonly isolated from infected hull pieces of peanut pod from farms or locations, and P. myriotylum was highest percentage isolated from severe rot pods or pods from spring crop season. Fusarium spp. populations density in soil of severe pod rot experimental field was higher than slight pod rot field, but were not significant different of correlation with pod rot severity or pH value or Ca concentration. 2. Over one thousand Germplasm and introduced varieties of peanut were screening for pod rot resistance at fields that had histories of supporting pod rot. Almost varieties were susceptible to pod rot, mean of pod rot for Spanish botanical type was slighter than other types. Four Valencia type varieties (VA111、VA114、VA220 and VA221)and one Virginia bunch type variety(VB186) those introduced from America had more resistance to pod rot disease(<20%). 3. Evaluated pod rot resistance character and agronomic characters for pod rot resistance varieties were cultivated continuously at a field in four crop seasons. Results crop seasons and varieties had an interaction for pod rot severity, and pods were more infected after severe pod rot disease seasons, but crop seasons were not main factor for pod rot severity. The correlation was positive for pod rot severity with leaf spot disease, were negative with pod and seed yield, others were not significant different of investigated 10 agronomic characters. 4. Treats with high concentration of Ca would reduced pod rot severity of peanut, and suggested a geocarposphere nutrient imbalance was main factor for peanut pod rot, were reported. But pod rot severity were not different effects to treat or not treat in ours researches, used a different peanut resistance varieties inoculated with four pathogens after treats with Ca and organic matter in pots. The pathogens were main factors for peanut pod rot, and P. myriotylum was most important pathogen. 5. For research pathogens interactions, four different pod rot resistance varieties were inoculated with four pathogens combined each other in pot. Highly resistance to pod rot disease variety (VB186) was low pod rot severity, but four varieties were susceptible to S. rolfsii that induced stem rot. The interactions were different in different variety with different inoculum treats alone or combinations of three pathogens. P. myriotylum was most important for pod rot severity of cultivars TP11 and resistance variety VB186, but not for other two varieties, in a component of variance analysis. 6. A diallel crosses analysis for pod rot resistance of peanut were conducted in greenhouse inoculation with P. myriotyrum and nature infected in field. Both additive and dominance effects were found significant in two sits. Additive was most important and a high heritability in greenhouse for pod rot severity, but dominance was important and low heritability in field. Partial dominance and polygene effects were found in greenhouse, but super dominance and at least one main gene were found in field. Pod rot resistance genes were mostly dominance in greenhouse, but were mostly recessive genes in field. Combining ability analysis indicated that significant variations due to the effects of general combining ability (GCA) and specific combining ability (SCA) were present for pod rot resistance, and GCA were mostly important in two sits. Maternal effects and reciprocal effects were found in two sits. Generations mean analysis indicated that epistasis were found in two crosses but different interaction effects.