Blast Resistance Of The Backcrossing Progenies From Transgenic Rice Introduced Lysozyme Gene And Their Cross Combinations Evaluation

ZH9(R) is a transgenic japonica rice line with a high resistance to rice blast, whichwas bred by the Institute of genetics and development Biology, Chinese Academy ofScience transforming a foreign lysozyme gene into the cultivar "Zhonghua 9" bybombardment. During 2001-2004 years, our research group had successfullytransferred the lysozyme gene from ZH9(R) into hybrid parents 9311,288,E32 bybackcrossing to breed transgenic blast-resistant indica rice. In this research, weevaluated the blast resistance of backcrossing progenies from transgenic rice, as wellas the resistance and agronomic traits of their hybrid combinations. The main resultswere as follows:1 Selection of the homozygous transgenic lines from backcrossing progeniesWith the antibiotic G418 screening combined with PCR testing on 83 transgenicbackcrossing lines in 7 different generations of 9311/ZH9(R), 288/ZH9(R) and E32/ZH9(R), we obtained 39 lines with homozygous lysozyme gene, the ratio being46.99%.2 Blast resistance evaluations of the transgenic lines from backcrossing progeniesWe had investigated the rice blast resistance level of transgenic backcrossing linesin the year 2005 and 2006.(1) Compared to the recurrent parents, the disease index of every transgenicbackcrossing generation had reduced to some extent. The disease index of leaf blastfor 288/ ZH9(R) BC₁F₅ had decreased by 70.99%, and that of spike blast forE32/ZH9(R) BC₃F₂ decreased by 7.79%. So we can conclude that the foreignlysozyme gene had stably inherited in the backcrossing progenies and provided abroad-spectrum resistance, merely its expression level was little different underdifferent genetic background. (2) The leaf blast resistances of transgenic backcrossing progenies had a positivecorrelation to their spike blast resistances. In general, the generation which had ahigher disease index for leaf blast presented a higher disease index for spike blast aswell. For example, 9311/ZH9(R) BC₄F₂ which had the highest disease index of 66.21for leaf blast, presented the.highest disease index of 50.94 for spike blast, howeverBC₃F₆ was the lowest disease index of 24.80 for leaf blast, presented the lowestdisease index of 25.39 for spike blast.(3) For the same backcrossing cultivar, the blast resistances of higher inbredgenerations from lower backcross generations were better than those of lower inbredgenerations from higher backcross generations, for example, BC₃F₆＞BC₅F₃ in9311/ZH9(R), BC₁F₅＞BC₃F₂ in 288/ZH9(R), and BC₁F₅＞BC₃F₂ in E32/ZH9(R).(4) In the same backcross generation, the blast resistances of inbred lines wereimproved gradually with the increase of inbred generations. According to theirappearances at Taojiang blast nursery, the spike blast resistance of BC₄F₂, BC₄F₃,BC₄F₄ and BC₄F₅ in 9311/ZH9(R) was 15.77%,26.05%,49.52% and 60.79%, that ofBC₂F₄ and BC₂F₆ in 288/ZH9(R) was 48.10% and 58.50%, and that of BC₂F₄, BC₂F₆in E32/ZH9(R) was 21.97% and 47.85%, respectively.(5) Twenty backcrossing lines were selected in two years, and their resistanceevaluation results at Taojiang and Liuyang disease nurseries were basically identical,of which seven lines were susceptible, nine middle-susceptible and threemiddle-resistant. However, the resistances of BC₂F₆ in E32/ZH9(R) were not identicalat above two nurseries, the former susceptible and the latter middle-susceptible.3 Evaluation of transgenic hybrid combinationsThrough the spike blast resistance and yield comparison, thirteen transgenic hybridcombinations of transferring offspring were selected, whose male parents came from9 individuals and 4 lines, respectively, and their resistances were better than those ofthe controls and the yields near to the controls. Selecting 5 cross combinations thattheir male parents is Individnal.