Cytogenetic studies on two F1 hybrids of autotetraploid rice varieties showing extremely high level of heterosis

Abstract

Abstract. Mechanisms of two F1 hybrids (D46A · DTP-4 and D46A · Dminghui63) of autotetraploid rice (2n = 4x = 48) showing extremely high pollen fertility 87.40% and 85.97%, respectively, seed set 82.00% and 79.00%, respectively and extremely high level of heterosis were analyzed cytologically. The chromosome pairing of D46A · DTP-4 and D46A · Dminghui63 was normal at metaphase I(MI), and had almost no I or III, with an average of 0.020I +14.36 II 6.44rod+7.91ring) +0.01III + 4.80 IV + 0.01VIII and 0.06 I + 17.67 II (11.01rod + 6.67ring)] + 0.06 III +3.10IV+ 0.01VI, respectively. The most frequent chromosome configurations were 10II+7IV and 12II+ 6IV. The bivalent frequency was less frequent in hybrids than that in restoring parents, and the same results were gained from univalents, trivalent and multivalents. However, the quadrivalent frequency was significantly higher in hybrids than that in restoring parents at MI. The other meiotic phases progressed normally, except for low percentages of PMCs with lagging chromosomes at AI and low percentages of PMCs with micronuclei at telophaseI (TI) and telophaseII (TII). PMCs with lagging chromosomes at AI and PMCs with micronuclei at TI and TII showed negative correlation between pollen fertility and seed set. Above 90% of the PMCs could form normal microspores, which resulted in the production of viable pollen grains, abnormal microspores were observed including penta-fission and hexa-fission. Based on these results we suggest that the two F1 hybrids had better behaviors of chromosome pairing and genetic stability than autotetraploid rice and other autotetraploid plants ever studied.

Agronomic Traits and Cytogenetic Evaluation of Newly Developed Autotetraploid Rice Line

“…Long et al (2007) considered that the autotetraploid rice maintainer lines with more number of quadrivalents exhibited more stable inheritance than the autotetraploid rice restorer lines, and believed that the increase in quadrivalents results in good chromosome pairing of maintainer lines. High percentage of trivalents and univalent were generally resulted in low seed setting of autotetraploid plants (Cai et al, 2007;Luan et al, 2007;He et al, 2011a,b;Wu et al, 2014). In our study, more number of quadrivalents were found in newly developed autotetraploid rice 1162 than that in its parents with low seed setting, while the frequency of trivalent and univalent was lower in the new line comparing with its parents at diakinesis and metaphase I.…”

“…Abnormal meiosis chromosome behavior, such as multivalents and univalents, happened frequently in autotetraploid plants, and was considered important reasons for low seed setting of the autotetraploids (Luan et al, 2007;Long et al, 2007;He et al, 2011a,b). Multivalents of chromosome included trivalents, quadrivalents, pentavalents, and so on, in autotetraploid plants.…”

“…The numbers of quadrivalents were approximately similar among the hybrids and their parents with different pollen fertility (Zhao et al, 2006). Luan et al (2007) studied the cytology of the autotetraploid restorer lines and found that univalents, trivalents and multivalents result in low seed setting, while the quadrivalent had nonsignificant correlation with seed setting. They considered that the number of quadrivalents within a range may not exert great effect on pollen fertility or seed setting.…”

Cytological and transcriptome analyses reveal abrupt gene expression for meiosis and saccharide metabolisms that associated with pollen abortion in autotetraploid rice

“…Autotetraploid rice has four sets of homologous chromosomes, and chromosome behaviour is more complicated in autotetraploid rice than in the diploid counterpart. Abnormal chromosome behaviour is a major reason for pollen abortion in autotetraploid rice (Luan et al 2007, 2009; He et al 2011a, b; Wu et al 2014). There are many types of abnormal chromosome behaviour in the autotetraploid rice, including chromosome straggling and chromosome lagging (Wu et al 2014).…”

High embryo sac fertility and diversity of abnormal embryo sacs detected in autotetraploid indica/japonica hybrids in rice by whole‐mount eosin B‐staining confocal laser scanning microscopy

“…Autotetraploid rice (2 n = 4 x = 48) derived from diploid rice (2 n = 2 x = 24) through chromosome doubling with colchicine is an excellent pool for desirable genes for resistance to pathogens and high protein content (Luan et al. 2007).…”