Flowering and fruiting phenology of jackfruit (Artocarpus heterophyllus Lam.) from Sumatra landraces in ex situ conservation area in Karangmojo, Yogyakarta

This study aimed to determine the flowering and fruiting phenology of jackfruit originated from Sumatra landraces planted in ex situ conservation in Yogyakarta within the 2018 and 2019 flowering periods. Flowering ontogeny and phenology were observed following Owens and Pushpakumara methods. Results found five developmental stages of male inflorescences, which last in 64-101 days, ended by the drought and abscissed of the males. Female inflorescences undergo five stages which take 92-160 days in total. Differences in rainfall and the dry season period resulted in different onset and duration of flowering. In 2018, which has more rainfall and a shorter dry season, flowering initiates lately (February-June) with a longer duration (6 months). In 2019, the less rainfall and more extended dry season resulted in early flowering (January-April) with a shorter duration (4 months). The Medan landrace flowered later and longer. Flowering synchrony occurred between sexes within the same tree, but there was asynchronous flowering among individual trees. Water availability is crucial in flowering and fruit production. Flowering stimulation and pollination management may also be conducted to increase flower production, pollinating agents, and fruit production and synchronize the flowering.

Weedy Rice Diversity in Southern Brazil

Weedy rice (Oryza sativa L.) is one of the most troublesome weeds affecting rice (Oryza sativa L.) production in many countries. Weedy rice control is difficult in rice fields because the weed and crop are phenotypically and morphologically similar. Weedy rice can be a source of genetic diversity to cultivated rice. Thus, this study aimed to characterize the morphological diversity of weedy rice in Southern Brazil. Qualitative and quantitative traits of 249 accessions from eight rice growing mesoregions in Rio Grande do Sul (RS) and Santa Catarina (SC) states were analyzed. For each accession, 24 morphological descriptors (14 qualitative and 10 quantitative) were evaluated. All the 249 accessions from RS and SC are of indica lineage. Considering all the phenotypic traits evaluated, the accessions separated into 14 distinct groups. One of the largest groups consisted of plants that were predominantly tall and with green leaves, intermediate shattering, and variable in flowering time. Distinct subgroups exist within larger clusters, showing discernable phenotypic diversity within the main clusters. The variability in flowering time was high (77 to 110 d after emergence), indicating high potential for flowering synchrony with rice cultivars and, consequently, gene flow. This indicates the need to remove escapes when planting herbicide-resistant rice. Thus, weedy rice populations in Southern Brazil are highly diverse and this diversity could result in variable response to weed management.

Effective Seed Yield and Flowering Synchrony of Parents of CIMMYT Three-Way-Cross Tropical Maize Hybrids

Genotype, environmental temperature, and agronomic management of parents influence seed yield in three-way cross hybrid maize seed production. The objective of this research was to generate information on the seed production of six three-way cross hybrids and their progenitors, adapted to tropical lowlands. Data on days to—and duration of—flowering, distance to spike and stigmas, and seed yield of five female single crosses and five male inbred lines were recorded for different combinations of four planting densities and four sowing dates in Mexico. The effect of planting density was not significant. The male inbred line T10 was the earliest and highest seed yield and T31 the latest, occupying second place in yield. The single crosses T32/T10 and T13/T14 were the earliest and had the highest effective seed yield. At the earliest sowing date, the females were later in their flowering, accumulated fewer growing degree days (GDD), and obtained higher yields since the grain-filling period coincided with hot days and cool nights. To achieve greater floral synchronization and therefore greater production of hybrid seed, differential planting dates for parents are recommended based on information from the accumulated GDD of each parent. The three-way cross hybrids were classified according to the expected seed yield of the females and the complexity in the synchronization of flowering of their parents.

Effect of F2 Inter se Mating on Quantitative Traits Mean, Range, Variance and Heritability in Dolichos Bean (Lablab purpureus L. Sweet var. Lignosus)

Background: Pedigree method of breeding in predominantly self-pollinated crop like dolichos bean enable exploiting only fixable genetic effects as a result of rapid increase in homozygosis. One or a few cycles of inter-mating in F2 generation help create populations with high frequency of desired recombinants which otherwise cannot be realized in later generations. The objective of the present investigation was to assess the impact of inter se mating in F2 population on nine quantitative traits’ (QTs) mean and variability parameters.Methods: Randomly selected 20 pairs of a single cross-derived F2 plants with flowering synchrony were inter se mated. Progenies derived from 20 paired crosses (designated as BIP F3 progenies) and those (F3) derived from their 40 F2 parents were evaluated for 9 QTs. Statistics such as mean, absolute range (AR) and standardized range (SR), variance (σ2), additive genetic variance (σ2A) and narrow-sense heritability (NS-h2) were estimated. BIP F3 progenies were compared with those of F3 progenies for QTs mean, AR/SR, σ2, σ2A and NS-h2. Significance of differences between BIP F3 progenies and F3 progenies for mean and σ2 were examined using two-sample t test and Levene’s tests, respectively. Result: The random mating in F2 population was effective in increasing the means, variances, σ2A and NS-h2 of racemes plant-1, fresh pods node-1, fresh pods plant-1 and fresh pod yield plant-1 in dolichos bean. Considering that random mating followed by selfing is a method of genetic improvement for future breeding rather than for immediate use, our results suggest long-term genetic gain and better prospects of deriving superior pure-lines with desired traits/combination of traits from inter-mated population in dolichos bean.

Intraspecific Seasonal Variation of Flowering Synchronization in a Heterodichogamous Tree

Heterodichogamous reproduction in plants involves two flowering morphs, reciprocal in their timing of male and female sexual functions. The degree of synchrony in floral sex phase, within and between individuals of each morph, determines the flowers’ potential fertilization partners. Complete within-morph synchrony enables across-morph mating alone, whereas unsynchronized floral sex phases may allow fertilization within a plant individual (geitonogamy) or within a morph. We documented the disruption of flowering synchrony in the heterodichogamous Ziziphus spina-christi towards the end of its seven-month flowering season. This desert tree has self-incompatible, protandrous, short-lived (2-day) flowers that open before dawn (‘Early’ morph) or around noon (‘Late’ morph). We counted flowers in the male and female phase on flowering branches that were sampled monthly during the 2016–2018 flowering seasons. In 2018, we also tagged flowers and followed their sex-phase distributions over two days at the start, middle, and end of the season. The switch to the female phase was delayed at the end-season (November-December), and 74% of the flowers did not develop beyond their male phase. Differences in male-phase duration resulted in asynchrony among flowers within each tree and among trees of both flowering morphs. Consequently, fertilization between trees of the same morph becomes potentially possible during the end-season. In controlled hand-pollination assays, some within-morph fertilizations set fruit. The end-season breakdown of synchronous flowering generates variability within morphs and populations. We suggest that this variability may potentially enable new mating combinations in a population and enhance its genetic diversity.