中文摘要：

【目的】明确单核枇杷形成的主要影响因素。【方法】以3个单核枇杷单株‘2-27’、‘10-6’、‘10-47’为试材,‘大五星’为对照,研究了单核枇杷花粉活力、离体萌发率和授粉受精亲和性,并进行了小孢子母细胞减数分裂行为和雌配子体发育进程的解剖学观察,并鉴定其倍性。【结果】3个单核枇杷都是三倍体;花粉畸形率高、离体萌发率极低,花粉母细胞减数分裂异常;二倍体花粉在单核枇杷柱头上有生长缓慢或停滞的现象,田间杂交所获子代全部为单核;单核枇杷中多见胚囊过早解体退化,导致大部分未受精胚珠过早败育。偶见1个子房中仅存1个正常胚珠,有望发育为单核果实。【结论】三倍体减数分裂过程中,染色体分离重组或不减数等形成低几率育性,最终获得的极少数有育性的配子才是形成单核的关键。

英文摘要：

[Objective]Loquat（Eriobotrya japonica.Lindl.） is an commercially important fruit tree,which belongs to the Rosaceae family and is native to southern China.One of the major problems which restricts the development of the industry is its low flesh recovery due to seediness.Normal diploid loquat fruit usually has 4-5 seeds and a very thin flesh layer,leaving only a 50%-60% flesh recovery.Seedless variety is one of the important targets of loquat breeding.Our research group has obtained several single-seeded loquat lines and collected some basic data such as fruit set,fruit weight,and yield per plant as well as total soluble solids（TSS） and titratable acids（TA）.We found that although the fruit set rate is very low,sometimes only 10-20 fruits per plant,all fruit are single-seeded,with a high flesh recovery of 75%-90%.TSS of the fruit is 10%-11%.The results suggested that the single-seeded loquat lines are a important germplasm resource.However,the mechanisms of the formation of the single-seed trait are still unclear.Seed degeneration or embryo abortion is generally observed during seed development in multi-seeded loquat cultivars,but it could not clearly explain why finally only one seed remained in each fruit.We believe that the single-seeded loquats might have some unique characters in seed formation.So we selected the single-seeded loquat as material to study the mechanisms and influence factors of single-seeded trait,with the purpose to provide theoretical evidence for breeding loquat cultivars with higher flesh recovery.[Methods]In this study,we used 3 single-seeded loquat lines ＇ 10-6＇,＇2-27＇ and ＇ 10-47＇ as materials,and normal diploid loquat variety ＇Dawuxing＇ as the control.First,flow cytometry（FCM） was used for loquat ploidy identification,and then TTC staining and pollen germination in medium（agarose gel containing different concentrations of sucrose） were used to test pollen viability.Meanwhile,single-seeded loquat was used to observe the pollen morphology by scanning e