Abstract

Rice is one of the most important food crops of the world which is grown in various agro climatic conditions and it encounters several biotic and abiotic stresses. Among biotic stresses bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae is the major destructive disease in the world. There is no chemical effective against this disease, so growing resistant varieties is the only way to decrease the losses caused by the disease. To develop durable resistance varieties in the particular area under biotic stress conditions necessitates evaluation of rice genotypes. The present study revealed significant fingerprinting variations observed among the 44 Xanthomonas oryzae pv. oryzae isolates from Tella Hamsa genotype collected from different areas, Gagillapur and Kompally. In addition, much diverse pathotypic variation or virulence pattern was detected from set of differentials containing near isogenic lines and traditional cultivar differentials. Virulence data obtained from these differentials revealed that all of them were compatible with the resistance genes. However, these pathotypes were incompatible with the genes, xa-5, Xa-10, xa-13 and Xa-21 suggesting the possibility of deploying them for enhancing the resistance. Similar observations were reported in the research area of rice crop improvement. So, this study suggests the deployment of genes in combinations of two and three expressed wide spectrum of longevity resistance to bacterial blight pathogen.

中文摘要

稻米是全世界最重要的糧食作物之一，並且栽植於不同的農業氣候區域，受到不同的生物性及非生物性的壓力。在生物性的壓力中，由Xanthomonas oryzae pv. oryzae 所引起的細菌性葉枯病是最主要的毁滅性疾病，目前並無有效的化學藥劑可以對抗此病。因此提高稻米本身的抗病性是減少此病造成損害的唯一方法。若要於某些具高生物性壓力的地區，培養出具高耐受度的抗病品系，需要評估稻米的基因型。由來自Gagillapur 及 Kompally 的44 株地區性高產量品系'Tella Hamsa'，分離出 Xanthomonas oryzae pv. oryzae 的基因型，本研究顯示出44 個分離株的DNA 鑑識結果有明顯的變異性。除此之外，由相近的等基因型品系差別型及傳統品系差別型，其致病性或毒性具有高變異性。由這些差別型獲得的毒性資料顯示它們皆與這些抗病性基因相容。具抗病基因而與致病型不相容之稻米品系有xa-5, Xa-10, xa-13 and Xa-21，顯示可藉由這幾個品系的基因型來誘發其他植株的抗病性。類似的報導亦在此稻米改良研究中出現過。因此本研究提出：可採用結合2 至3 種對細菌性枯葉病具長效抗病性的寬譜系來誘發稻米的抗病性。

Keyword: Rice, DNA fingerprinting, UPGMA, disease resistance and pathotyping. 稻米、DNA 鑑識、UPGMA (不加權平均連結)、抗病性、致病型。