Application of a probabilistic model for analysing the abortion of seeds and pods in winter oilseed rape (Brassica napus)

Abstract

International audienceIn winter oilseed rape (WOSR), only a subset of ovules can develop into seeds in the majority of pods. Any difficulty during the process of seed production may result in seed or pod abortion. This study aimed to reproduce the process of seed development in WOSR based on a limited number of parameters. As a result of the complexity of the developmental patterns of WOSR, it is challenging to identify the roles of various factors that influence seed production using an experimental approach. Here, we present a stochastic probabilistic model of seed development. The generalised least squares method was implemented to estimate the model parameters using the experimental data. Experiments were done in Grignon (France) in 2008 and 2009. The variations in the parameters were analysed according to the following four factors: year, pod rank, inflorescence position and ramification-clipping treatment. The year had no effect on the number of ovules per ovary (í µí¼‡) and the probability of seed viability (p). The proportion of effective pollen grains (k) significantly decreased with pod rank at the end of the main stem. Inflorescence position influenced the number of ovules per ovary (í µí¼‡: 30.8–33.8 from top to bottom) and the parameter k. The mean number of seeds per pod on the main stem and the bottom ramification along the stem was larger than the other ramifications within one plant. Ramification-clipping treatment increased the number of ovules per ovary (í µí¼‡: 31 for control plants and 32 for clipped plants), the parameter k and the number of seeds per pod (p). This effect could be due to the competition for assimilates between the pods and seeds. Furthermore, the distribution parameters of the pollen number per stigma (m) remained stable, and the probability of pod survival (Bo) varied with different factors, including the year, pod rank and inflorescence position. Our results indicate that pollen germination is a factor that determines final seed number. This model can identify the impact of each of the factors that lead to the abortion of seeds and pods in WOSR, which include the position effect, assimilate competition and pollination limitation. However, further studies on the pollination process in WOSR should help to refine this model

Variable pollen viability and effects of pollen load size on components of seed set in cultivars and feral populations of oilseed rape

“…Moreover, no seeds were produced for crosses with the largest pollen load size (> 500 pollen grains). Reduced seed set for larger pollen loads could be caused by pollen clogging of the stigma [ 15 ] or seed abortion, which is common in this species [ 43 ].…”

Pollen number and vigor contribute to effective ovule numbers among contrasting nitrogen utilization efficiency oilseed rapes genotypes before heart stage

“…6) mainly resulted from larger filled pod number (EON), which associated with higher pollen number, better pollen vigor, and a low success ratio of developed pods (ovule abortion rate). The process from the initial ovule to final seeds is affected by many factors, such as pollen sterility [5], pollen tube growth [29], floral bud quantity [30], inflorescence position [16], planting density [17], shading [18] and silique photosynthesis [31]. In this study, we explored the main factors that may have caused diverse EON in two perspectives: before and after ovule fertilization.…”

“…The number of ovules per placenta was reported to be determined by the process of ovule differentiation and development [15]. The frequency of embryonic abortions of oilseed rape was determined by the fertilization process, which is dependent on many factors such as pollen grain germination [16], silique photosynthesis [17,18], nutrition accumulation [19] and the number of flowers [20,21]. Although from the ovule fertilization to seed maturity, the developmental processes among oilseed rape genotypes could be largely clear, there is little knowledge of the main factors that determine the final EON before fertilization.…”

Pollen Grain Number and Viability Contribute to Variation in Effective Ovule Number Among Oilseed Rape Genotypes

“…Biologically, the EON of oilseed rape genotypes is primarily determined by the number of owers initiated, the number of ovules per placenta, the proportion of ovules to be fertilized (the proportion of fertile ovules × the proportion of fertile ovules to be fertilized), the proportion of fertilized ovules to develop into seeds as well as the frequency of embryonic abortions (the proportion of fertilized ovules to develop into seeds) (Jeong et al 2012;Yang et al 2016;Yang et al 2017b). Embryonic abortion, which occurs at different developmental stages within the fruit, has been shown to be non-random and based on the genotype of the embryo and environmental factors as well as their interaction (Calvino 2014), such as pollen grain germination (Wang et al 2014), silique photosynthesis (Khan et al 2018;Labra et al 2017), nutrient accumulation (Li et al 2020) and the number of owers (Wang et al 2011;Brookes et al 2010). Although the developmental processes from the ovule fertilization to seed maturity is well known among oilseed rape genotypes, there is a paucity of knowledge that pinpointed the main factors that determine the EON, especially in pollen indices.…”