Seed Set Percentage Research Articles

Assessment of genetic variability, heritability and correlation in advanced breeding lines of bread wheat (Triticum aestivum) under heat stress condition

Abstract An experiment was conducted under normal (with six irrigation during crop period) and stressed condition during Rabi 2019 in All India Coordinated Research Project (AICRP) on Wheat, MARS, Dharwad, Karnataka with the view of assessing genetic variability, heritability and expected genetic advance in 104 F4 families of the cross HD2864 × DBW14. The progenies exhibited wide range of variation for all the traits indicating the presence of enough genetic variability in the material under study. Under timely sown condition, the traits like leaf waxyness, NDVI at different stages, SPAD at different stages, number of productive tillers per plant, seeds per spike, grain filling duration, spike length, thousand grains weight and seed set percentage showed high variability. The traits like plant height, canopy temperature at different stages and membrane stability index showed low variability. Under late sown condition, the traits like leaf waxyness, plant height, NDVI at different stages, SPAD at different stages, number of productive tillers per plant, seeds per spike, yield per plant, row bulk yield and seed set percentage showed high variability. The traits like days to maturity, spike length and membrane stability index showed low variability. The findings shows that all traits related to crop yield are positively linked, except for canopy temperature at different growth stages. Promising lines identified through Heat susceptibility index (HSI) and Heat tolerance index (HTI) can be utilized in future breeding programs to enhance crop productivity. Keywords: Variability, Coefficient of variation, Heritability, Genetic advance.

Comparative Proteomic Analysis Provides New Insights into Improved Grain-filling in Ratoon Season Rice

Grain-filling of rice spikelets (particularly for the later flowering inferior spikelets) is an important characteristic that affects both quality and yield. Rice ratooning technology is used to cultivate a second crop from dormant buds that sprout from stubble left after the first harvest. This study used two rice varieties, the conventional indica rice ‘Jinhui 809’ and the hybrid indica-japonica rice ‘Yongyou 1540’, to assess the impact of rice ratooning on grain-filling. The results indicated that the grain-filling process in inferior spikelets of ratoon season rice (ISR) showed significant improvement compared to inferior spikelets of main crop (late season) rice (ISL). This improvement was evident in the earlier onset of rapid grain-filling, higher seed-setting percentage, and improved grain quality. A label-free quantitative proteomic analysis using mass spectrometry identified 1724 proteins with significant abundance changes, shedding light on the molecular mechanisms behind the improved grain-filling in ISR. The functional analysis of these proteins indicated that ratooning stimulated the metabolic processes of sucrose-starch, trehalose, and hormones in rice inferior spikelets, leading to enhanced enzyme activities related to starch synthesis, elevated concentrations of trehalose-6-phosphate (T6P), indole-3-acetic acid (IAA) and zeatin riboside (ZR) during the active grain-filling phase. This research highlighted the importance of the GF14f protein as a key regulator in the grain-filling process of ISR. It revealed that GF14f transcriptional and protein levels declined more rapidly in ISR compared to ISL during grain-filling. Additionally, the GF14f-RNAi plants specific to the endosperm exhibited improved quality in inferior spikelets. These findings suggest that the enhancement of starch synthesis, increased levels of IAA, ZR, and T6P, along with the rapid decrease in GF14f protein, play a role in enhancing grain-filling in ratoon season rice.

Sorghum drought tolerance is enhanced by cerium oxide nanoparticles via stomatal regulation and osmolyte accumulation

Sorghum [Sorghum bicolor (L.) Moench] yield is limited by the coincidence of drought during its sensitive stages. The use of cerium oxide nanoparticles in agriculture is minimal despite its antioxidant properties. We hypothesize that drought-induced decreases in photosynthetic rate in sorghum may be associated with decreased tissue water content and organelle membrane damage. We aimed to quantify the impact of foliar application of nanoceria on transpiration rate, accumulation of compatible solutes, photosynthetic rate and reproductive success under drought stress in sorghum. In order to ascertain the mechanism by which nanoceria mitigate drought-induced inhibition of photosynthesis and reproductive success, experiments were undertaken in a factorial completely randomized design or split-plot design. Foliar spray of nanoceria under progressive soil drying conserved soil moisture by restricting the transpiration rate than water spray, indicating that nanoceria exerted strong stomatal control. Under drought stress at the seed development stage, foliar application of nanoceria at 25 mg L−1 significantly improved the photosynthetic rate (19%) compared to control by maintaining a higher tissue water content (18%) achieved by accumulating compatible solutes. The nanoceria-sprayed plants exhibited intact chloroplast and thylakoid membranes because of increased heme enzymes [catalase (53%) and peroxidase (45%)] activity, which helped in the reduction of hydrogen peroxide content (74%). Under drought, compared to water spray, nanoceria improved the seed-set percentage (24%) and individual seed mass (27%), eventually causing a higher seed yield. Thus, foliar application of nanoceria at 25 mg L−1 under drought can increase grain yield through increased photosynthesis and reproductive traits.

Differential Expression of Restorer Gene on Different Nuclear Background with Maldandi cytoplasm in Sorghum (Sorghum bicolor (L.) Moench)

To investigate the expression of restorer gene on different nuclear background an experiment was carried out using six iso-plasmic male sterile lines with maldandi cytoplasm, and each having different nuclear background. These lines were hybridized with a strong and stable restorer to generate six iso-plasmic hybrids at Main Agricultural Research Station (MARS), UAS Dharwad during rabi -2020-21. These hybrids were then evaluated for pollen fertility and seed set percentage during rabi -2021-22. The results found that, pollen fertility percentage of six iso-plasmic hybrids ranged from 69.82 per cent for ICSA 88004 A4 (M) × DSMR 8 to 92.42 per cent for M31-2A (M) × DSMR 8. Similarly, for seed set percentage M31-2A (M) × DSMR 8 and ICSA 88004 A4 (M) × DSMR 8 exhibited highest (85.17 per cent) and lowest (61.19 per cent), respectively. All the six iso-plasmic hybrids had varied expression for pollen fertility and seed set percentage which suggests that the restorer gene expressed differentially in different nuclear genome of female parent. The probable reasons for variation in fertility restoration behaviour are, abundance of inhibitors in the female parent or variation in the expressivity of restorer gene or influence of minor or modifier genes in the restorer parent or interaction between nuclear genes of both the parents.

Studies in the seed ecology and seedling Phenology of Andrographis paniculata (Brum. f.) Wall. ex Ness in West Bengal, India

Andrographis paniculata (Brum. f.) Wall. ex Nees is an important medicinal plant of tropical Asia and has been used widely for a long time for different clinical ailments. Despite profuse flowering and a high percentage of fruit set,the number of seedlings in the natural population is the bare minimum. Knowledge regarding the seed ecology and seedling phenology of A. paniculata, is needed to formulate conservation strategies for the species. Therefore, a detailed study on seed ecology and seedling phenology has been conducted. During seed ecological studies,seed production, seed-set percentage, seed-ovule ratio, mechanism of seed dispersal, seed structure along with germination status, viability, dormancy and its breaking, and percentage of moisture content loss have been studied. Seeds exhibit some kind of dormancy [germination percentage (GP) = 28.51 ± 0.98, mean germination time (MGT) = 33.07± 0.89 days, and germination index (GI) = 0.73 ± 0.08] which can be effectively overcome through acid scarification using H2SO4 and hot water treatment. The species shows epigealphanerocotylar germination. The hypocotyls exhibit rapid growth, and cotyledons emerged at 7.52±0.27 TARA (Time After Radicle Appearance in days). Seedling is characterised by a thickened, hairy hypocotyl, a distinct collet, a pair of paracotyledons, and three pairs of eophylls in opposite decussate phyllotaxy. The studies on seed ecology and seedling phenology play a significant role in understanding how the shortening of the inception period enhances the germination status, and distinct seedling morphology provides the opportunity to formulate conservation strategies in their wild habitat.

Correlation and path analysis of yield traits in B & R lines of rabi sorghum [Sorghum bicolor (L.) Moench

The present investigation was carried out for correlation and path coefficient analysis using 32 rabi sorghumhybrid parents including maintainers (B) and restorer (R) lines for grain yield and its attributes. The experimental materialwas evaluated during rabi season 2021-22 at Regional Agricultural Research Station, Vijayapur in randomized block designwith two replications. The character association studies revealed that grain yield per plant was found to be significantly andpositively correlated with days to 50% flowering, plant height, panicle breadth, panicle weight, harvest index, panicleharvest index, seed set percentage and grain number per plant both at genotypic and phenotypic level. Path analysisrevealed that characters such as panicle weight, panicle harvest index, harvest index, fodder yield per plant, days to 50%flowering and SPAD at physiological maturity showed a positive direct effect on grain yield per plant. These traits can beconsidered as principal yield determining components and it is suggested to use these as indirect selection criteria for B andR-line improvement.

Identification of SSR markers linked to new fertility restoration trait in sorghum (Sorghum bicolor (L.) Moench) for A4 (maldandi) male sterile cytoplasm

AbstractIdentification of markers associated with fertility restoration (Rf) genes is essential because they can streamline the breeding of new CMS lines and production of commercial hybrid seeds. Therefore, in the present study, F2 populations (M31‐2A × DSMR 8) was utilized to identify markers linked to Rf loci on maldandi (A4) cytoplasm through bulk segregant analysis (BSA). The F2 population was analysed for seed set percentage. Chi‐square (χ2) analysis showed that the fertility restoration trait followed expected digenic ratio. By BSA, simple sequence repeats (SSRs) markers, namely, Xtxp 34 and Xtxp 69 located on chromosome 3 and SB 3956 and Xtxp 312 located on chromosome 7, showed clear polymorphism between two groups of fertile and sterile bulks. The genomic region harbouring Rf locus on chromosome 3 (2.61 Mbp) predicted to encode five pentatricopeptide repeat (PPR) genes whereas, on chromosome 7, the gene SORBI_3007G047400 predicted to encode MYB (myeloblastosis) domain containing proteins. These predicted genes could be the candidate for restoring fertility on A4 cytoplasm. This finding will be fundamental in the production and rapid selection of novel restorer lines.

Combining Ability Analysis of Yield-Related Traits of Two Elite Rice Restorer Lines in Chinese Hybrid Rice.

Hybrid rice breeding is an important strategy for enhancing grain yield. Breeding high-performance parental lines and identifying combining abilities is a top priority for hybrid breeding. Yuenongsimiao (YNSM) and its derivative variety Yuehesimiao (YHSM) are elite restorer lines with a high ability of fertility restoration, from which 67 derived hybrid combinations have been authorized to different degrees in more than 110 instances in China. In this study, we found that YNSM and YHSM contained three candidate restorer-of-fertility (Rf) genes, Rf3, Rf4, and Rf5/Rf1a, that might confer their restoration ability. Subsequently, we investigated heterosis and combining ability of YNSM and YHSM using 50 F1 hybrids from a 5 × 10 incomplete diallelic mating design. Our results indicated that hybrid combinations exhibited significant genetic differences, and the additive effects of the parental genes played a preponderant role in the inheritance of observed traits. The metrics of plant height (PH), 1000-grain weight (TGW), panicle length (PL), and the number of spikelets per panicle (NSP) were mainly affected by genetic inheritance with higher heritability. Notably, the general combining ability (GCA) of YHSM exhibited the largest positive effect on the number of grains per panicle (NGP), NSP, PL, and TGW. Thus, YHSM had the largest GCA effect on yield per plant (YPP). In addition, the GCA of YNSM exhibited a positive impact on YPP, mainly due to the critical contribution of seed setting percentage (SSP). Moreover, YNSM and YHSM exhibited negative GCA effects on PH, implying that YNSM and YHSM could effectively enhance plant lodging resistance by reducing the plant height of the derived hybrids. Remarkably, among the hybrids, Yuanxiang A/YNSM (YXA/YNSM), Shen 08S/Yuemeizhan (S08S/YMZ), and Quan 9311A/YHSM (Q9311A/YHSM) represent promising new combinations with a higher specific combining ability (SCA) effect value on YPP with a value more than 3.50. Our research thus highlights the promising application for the rational utilization of YNSM and YHSM in hybrid rice breeding.

Evaluating honeybee (Apis mellifera L.), as a potential pollinator to enhance the yield and yield attributes in hybrid sunflower (Helianthus annuus L.)

Sunflower is a protandrous type, having a problem in which male and female elements mature at different times. Hence, cross pollination is the only way for seed setting in sunflower. For effective cross pollination, various techniques were developed. Based on this, field study was conducted during June 2022-August 2022 at the Experimental Farm, Department of Agronomy, Annamalai University, Annamalai Nagar, Tamil Nadu to enhance the yield and yield attributes of hybrid sunflower (Kaveri Champ) through honeybee as an agent for cross pollination. The study comprised six treatments with four replications. The treatments were: T1–Natural pollination, T2–Hand pollination, T3–Head to head pollination, T4–Beehive alone, T5–Beehive + Hand pollination and T6–Beehive + Head to head pollination. The study revealed that the (T5) Beehive + hand pollination showed the highest value in terms of seed yield (3669 kg/ha), number of filled seeds per head (1418), 100-seed weight (4.72 g) and seed set percentage (98.55) followed by (T4) Beehive alone. Natural pollination (T1) showed the lowest seed yield (2088 kg/ha), number of filled seeds per head (832), 100-seed weight – (4.12 g) and seed set percentage – (71.91) in all the yield parameters. Pollination with honeybees and by hand increased seed yield per head, compared to natural pollination. Results indicated that the use of honeybees for sunflower hybrid improved the yield and yield attributes of sunflower.

Peculiarities of the development of reproductive organs of ornamental crabapples (Malus spp.) depending on drought resistance

The current task for both pomiculture and ornamental horticulture is the formation of plant cultivars resistant to different environmental stress and maintaining their high productivity. Drought is one of the most significant environmental factors that inhibit plant growth and development and cause a set of morphological, physiological, and biochemical changes in plant organisms. The aim of our research was to discover the relationship between the development of the reproductive organs of ornamental crabapples and the physiological indicators determined by drought stress factors. The four species and three cultivars of the ornamental crabapples (Malus spp.) from the collection of the National Dendrological Park “Sofiyivka” of NAS of Ukraine were involved in the study: M. × floribunda Siebold ex Van Houtte, M. halliana Koehne, M. niedzwetzkyana Dieck, M. × purpurea (A. Barbier) Rehder, M. × purpurea ‘Ola’, M. × purpurea ‘Royalty’, and M. × purpurea ‘Selkirk’. Drought resistance was determined by the following quantitative indicators: leaf water content, relative turgidity, leaf water deficit, and excised leaf water retention capacity. The leaf water content ranged from 60.0% (M. × floribunda) to 67.2% (M. × purpurea), the relative turgidity ranged from 81.7% (M. × purpurea ‘Ola’) to 98.9% (M. halliana), and the leaf water deficit ranged from 6.8% (M. halliana) to 24.4% (of M. niedzwetzkyana). As a result, the leaves of M. halliana lost the smallest amount of water in 24 hours (50.2%), whereas M. × purpurea 'Ola' leaves lost the largest amount (77.4%). The development of the reproductive organs was estimated based on the fertility and viability of pollen grains, percentage of fruit and seed set. Pollen fertility ranged from 79.8% (of M. niedzwetzkyana) to 95.0% (M. × purpurea 'Ola'); its viability varied from 5.1% (M. niedzwetzkyana) to 51.5% (M. × floribunda). The highest fruit set percentages were recorded in M. floribunda (80.5%), while the lowest was in M. × purpurea 'Royalty' (16.4%). The average percentage of seed sets was 48.5%. The development of the reproductive organs of Malus specimens depended on their drought resistance. The fruit and seed set percentages had a strong negative correlation with the water deficit in leaves determined during the period of drought stress. The percentage of fruit set was also strongly correlated with relative turgidity. The leaf water deficit and relative turgidity were the most important physiological indicators in the drought resistance study, taking into account the need to maintain crop yield and the decorative effect of Malus plants.

Evaluation of Advanced Mutant Restorer Lines for Enhancing Outcrossing Rate and Hybrid Seed Production of Diverse Rice Cytoplasmic Male Sterile Lines

Hybrid rice seed production predominantly relies on the pollen ability of restorer lines and the stigma properties of the cytoplasmic male sterile (CMS) lines. Improving the pollen ability and agronomic performance of restorer lines could be achieved using mutation to reinforce the outcrossing rate and seed set percentage of CMS lines. Two commercial restorer cultivars (Giza-178 and Giza-179) were treated with three different doses of gamma-ray; 200, 300, and 400 Gy. The derived mutant restorer lines were selfed and constantly evaluated with their corresponding parental cultivars until the M6 generation. Six promising mutant lines were chosen based on their performance to be evaluated with their parents for their pollen and agronomic characteristics. The novel-induced mutant restorer lines exhibited significant differences in all studied pollen and agronomic characteristics. The mutant restorer lines R4 and R7 exhibited superior desirable anther length (2.36 and 2.38 mm, in the same order), anther width (0.47 and 0.45 mm), pollen fertility (97.50 and 97.31%), basal pore length (218.8 and 299.5 mm), apical length (103.6 and 108.1), number of pollen grains per anther (1810 and 1832), plant height (121.8 and 115.9 cm), fertile tillers (23.50 and 18.89), number of spikelets per panicle (203.2 and 202.5), panicle length (25.34 and 24.26 cm), number of filled grains per panicle (195.5 and 191.8), seed set percentage (95.56 and 96.63%), and grain yield (11.01 and 11.36 t/ha). Based on the results of the first two seasons, the two novel promising restorers and their parental cultivars were crossed with four diverse CMS lines. The seed set percentage and hybrid seed production of the crossed CMS lines were evaluated for further two seasons. The results exposed that the combinations derived from restorer lines R4 and R7 with most of the evaluated CMS lines produced the uppermost seed set percentage outcrossing rate. Particularly in combination with CMS2, the restorer lines R4 and R7 displayed the highest seed set percentage (39.57 and 34.80%), number of tillers fertile per hill (25.31 and 23.32), seed yield (2.02 and 1.81 t/ha), and harvest index (23.88 and 22.66%). Conclusively, the derived gamma-ray-induced mutant restorer lines R4 and R7 could be exploited as a new source for ensuring desirable pollen and anther characteristics in order to improve the outcrossing rate of CMS lines and hybrid rice seed production.

Grain yield improvement in high-quality rice varieties released in southern China from 2007 to 2017

In recent years, high-quality rice varieties have been widely cultivated for food production in southern China. However, changes in the yield performance of different high-quality rice varieties are still unclear. In this study, the yield and yield components of 710 different types (hybrid or inbred rice and japonica or indica) of high-quality rice varieties were investigated in six provinces from 2007 to 2017. The results showed that, from 2007 to 2017, the grain yield and yield traits, including the number of spikelets per panicle and seed-set percentage, of high-quality indica rice varieties increased significantly, while the number of panicles decreased only in indica inbred rice. The grain yield of high-quality japonica rice also increased significantly, whereas japonica hybrid rice increased the number of spikelets per panicle and decreased the number of panicles. Compared with inbred rice, hybrid rice had a significant increase in grain yield due to a higher number of spikelets, rather than a lower number of panicles and seed-set percentage. Meanwhile, japonica rice showed higher grain yield than indica rice, which was attributed to seed-set percentage and an optimized structure between the number of panicles and the number of spikelets. In addition, the coefficient of variation of the grain yield of japonica rice decreased, whereas that of indica rice increased over time, and those of the number of panicles and seed-set percentage remained stable. Among the six provinces, Zhejiang had the highest grain yield because the number of spikelets per panicle and seed-set percentage increased over time. Our results suggested that, based on an increase in the yield potential of high-quality rice varieties over the past 11 years, future breeding of high-quality rice should be emphasized to improve the number of panicles and seed-set percentage for hybrid rice and the number of spikelets for inbred rice, especially the grain weight for indica inbred rice.

Comprehensive QTL analyses of nitrogen use efficiency in indica rice.

Nitrogen-use efficiency (NUE) in rice is a complex quantitative trait involved in multiple biological processes and agronomic traits; however, the genetic basis and regulatory network of NUE remain largely unknown. We constructed a high-resolution microarray-based genetic map for 261 recombinant inbred lines derived from two indica parents. Using 2,345 bin markers, comprehensive analyses of quantitative trait loci (QTLs) of seven key agronomic traits under two different N levels were performed. A total of 11 non-redundant QTLs for effective panicle number (EPN), 7 for grain number per panicle, 13 for thousand-grain weight, 2 for seed-setting percentage, 15 for plant height, 12 for panicle length, and 6 for grain yield per plant were identified. The QTL regions were as small as 512 kb on average, and more than half spanned an interval smaller than 100 kb. Using this advantage, we identified possible candidate genes of two major EPN-related QTLs. One QTL detected under both N levels possibly encodes a DELLA protein SLR1, which is known to regulate NUE, although the natural variations of this protein have not been reported. The other QTL detected only under a high N level could encode the transcription factor OsbZIP59. We also predicted the possible candidate genes for another three of the NUE-related QTLs. Our results provide a reference for improving NUE-related QTL cloning and promote our understanding of NUE regulation in indica rice.

Pollination efficiency and foraging behaviour of honey bees and flies to onion Allium cepa L.

Bees and flies are the most common visitors to onion flowers in Karnataka, but evidence for their pollination efficiency is lacking. Hence, experiments on pollination efficiency and behavioral observations were recorded using four bees (Apidae: Hymenoptera) and two flies (Syrphidae: Diptera) species visiting onion flowers (Allium cepa L.) at the experimental fields of ICAR-Indian Institute of Horticultural Research, Bengaluru, Karnataka, India (13.13°N; 77.49°E) during 2020-2021. Pollinator effectiveness (PE) is measured as pollen deposition on stigmas per visit. Honey bees and flies mainly collect nectar and stingless bees mainly pollen (81.90%), bringing the latter into intimate contact with the stigma more frequently. Stingless bees, honey bees and flies were often seen foraging together on the same umbel, and no antagonistic interactions were observed. The rock bee (Apis dorsata) deposited a maximum number (34.60) of pollen on stigma per visit followed by the stingless bee (24.45). The flowers pollinated by bees had a higher seed set percentage; the weight of 1000 seeds and the average number of seeds/umbels were higher compared to flowers deprived of pollinators. The results allowed us to conclude that bees are the effective pollinators of onions. Further work is needed to determine the optimum bee population required for maximizing the seed yield in onion.

Pollinator activity and their role on seed set of medicinal and aromatic Lamiaceae plants

Lamiaceae is one of the most economically important plant families based on their aromatic, medicinal, and industrial significance. In the present study three species of the Lamiaceae subfamily, Nepetoideae (Ocimum basillicum, Nepeta cateria, Leucas aspera) and one species from Lamioideae (Rosmarinus officinalis) were selected to document the pollinator bee diversity, foraging behavior, and their role on seed set. Thirty-two species of bees representing three families of Hymenoptera, (Apidae (94.87%) followed by Megachilidae (3.74%) and Halictidae (1.40%) were observed in all four plant species. Non-Apis bees were more abundant (69.35%) than Apis species (30.65%). The species-level variation in pollinator bees was observed in each plant species irrespective of space, time, and environmental conditions. O. basillicum attracted the maximum number of pollinator species (22) followed by R. officinalis (14) and L. aspera (10) and N. cataria (5). In O. basillicum, Ceratina species were major flower visitors, whereas R. officinalis was mainly visited by both Ceratina and Apis sp. L. aspera was dominated by Amegilla species and N. cataria mostly visited by the Apis bee species. However, irrespective of the diversity, the abundance of pollinator activity mainly contributed to enhancing the maximum number of seeds set in each species up to 64% overall increase under open pollination compared to bagged conditions. Also, a significant reduction in the seed set percentage was observed in R. officinalis and L. aspera under bagged pollination conditions. This indicates the high dependency of Lamiaceae plants on bee pollinators to maintain their reproduction and regeneration activities.

Racial Hybridization and Inbreeding Depression in Cedrus deodara (Roxb.) G. Don.

Aim of the study: This study aims to establish the inter-racial hybridization in Cedrus deodara from Garhwal Himalaya, India. Material and methods:Racial hybridization was conducted successfully in Cedrus deodara taking pollen (male gamete) from three different races/populations, i.e. Dhanoulti, Pauri and Harsil (locality-specific) at Dandachali population where female/ovulate cones were selected as mother trees. Main results:The results revealed that cone and seed set percentages in the selected races varied from 58.8 to 68.2 % and 79.0 – 86.2 %, respectively. Manual pollination resulted 0.972 and 0.953 inbreeding depression for cone and seed set, respectively. Highlights: C. deodara proclaimed high inbreeding depression at embryonic stage also manifests high compatibility for developing hybrids in its natural range of growth in Himalaya.

Heritability estimates for seed yield and its components in <i>Cynodon dactylon</i> var. <i>dactylon</i> (L.) Pers.

Bermudagrass [<italic>Cynodon dactylon</italic> var. <italic>dactylon</italic> (L.) Pers.] is a major warm-season turf and forage grass in the world. Seed yield is an important trait targeted for improvement in bermudagrass breeding programs because of the increased interest in seed-propagated cultivars. Understanding the nature of genetic variation for seed yield and its components in bermudagrass would aid the development of seed-propagated cultivars. The objective of this study was to estimate the genetic variation and narrow-sense heritability for seed yield and its two major components, inflorescences prolificacy and seed set percentage in bermudagrass. Twenty-five half-sib families and their respective clonal parents were evaluated at two Oklahoma locations, Perkins and Stillwater in two years. Half-sib families were different for seed yield, inflorescences prolificacy and seed set percentage, indicating the expression of additive genes in controlling these traits. Family × location effects were observed for seed set percentage and seed yield. All three traits showed family × year interaction effects. There was a significant family × location × year interaction in inflorescences prolificacy and seed set percentage. Narrow-sense heritability estimates for seed yield was 0.18 based on variance component analysis among half-sib families and ranged from 0.26 to 0.68 based on parent-offspring regressions, indicating genetic complexity of seed yield. Heritability estimates were moderate (0.30−0.55) for inflorescences prolificacy and moderate to relatively high (0.41−0.78) for seed set percentage. The results indicate that sufficient magnitudes of additive genetic variation for seed set percentage and inflorescence prolificacy permit positive response to selection and conventional progeny-based genotypic evaluation is necessary for seed yield improvement.

Heat Stress Affects Seed Set and Grain Quality of Vietnamese Rice Cultivars during Heading and Grain Filling Period

Environmental stress trigger a variety of rice plant response, ranging from alters seed set, grain yield and grain quality during flowering and grain filling stage. Efforts are required to improve our understanding of the impact of heat stress on rice production, which are essential strategies in rice cultivation. This article investigated the seed set, yield components and grain yield of Vietnamese rice cultivars (Indica germplasm) under high temperature environment during the flowering and grain filling stage. Six rice cultivars, including popular cultivars and new cultivars of Cuu Long Delta Rice Research Institute, and one popular extraneous cultivar with differences in maturing time, were grown in pots at high temperature (HT) and natural temperature condition as control (CT). All rice cultivars were subjected to the high temperature starting from the heading stage to the harvest maturity, applied by greenhouse effect. The greenhouse has about 25 cm window opening on 3 sides for air ventilation. The seed set rate of the heat-sensitive rice genotypes decreased significantly under HT, leading to a significant reduction in grain yield. The lowest seed set was recorded in “OM4900” (44.3%) and “OM18” (39.9%) under high temperature environment. The lower yield in all rice cultivars at an elevated temperature resulted in a dramatic decrease of filled grains and contributed to a loss of 1000-grain weight. ‘“OM892” is a potential rice cultivar for heat tolerant breeding program due to the seed set percentage was above 80% in both HT and CT conditions. High temperature during the grain filling stage resulted in a decreased amylose and increased chalkiness for all OM cultivars.

Abnormal anther development leads to lower spikelet fertility in rice (Oryza sativa L.) under high temperature during the panicle initiation stage

BackgroundDecreased spikelet fertility is often responsible for reduction in grain yield in rice (Oryza sativa L.). In this study, two varieties with different levels of heat tolerance, Liangyoupeijiu (LYPJ, heat susceptible) and Shanyou63 (SY63, heat tolerant) were subjected to two temperature treatments for 28 days during the panicle initiation stage in temperature/relative humidity-controlled greenhouses: high temperature (HT; 37/27 °C; day/night) and control temperature (CK; 31/27 °C; day/night) to investigate changes in anther development under HT during panicle initiation and their relationship with spikelet fertility.ResultsHT significantly decreased the grain yield of LYPJ by decreasing the number of spikelets per panicle and seed setting percentage. In addition, HT produced minor adverse effects in SY63. The decreased spikelet fertility was primarily attributed to decreased pollen viability and anther dehiscence, as well as poor pollen shedding of the anthers of LYPJ under HT. HT resulted in abnormal anther development (fewer vacuolated microspores, un-degraded tapetum, unevenly distributed Ubisch bodies) and malformation of pollen (obscure outline of the pollen exine with a collapsed bacula, disordered tectum, and no nexine of the pollen walls, uneven sporopollenin deposition on the surface of pollen grains) in LYPJ, which may have lowered pollen viability. Additionally, HT produced a compact knitted anther cuticle structure of the epidermis, an un-degraded septum, a thickened anther wall, unevenly distributed Ubisch bodies, and inhibition of the confluent locule, and these malformed structures may be partially responsible for the decreased anther dehiscence rate and reduced pollen shedding of the anthers in LYPJ. In contrast, the anther wall and pollen development of SY63 were not substantially changed under HT.ConclusionsOur results suggest that disturbed anther walls and pollen development are responsible for the reduced spikelet fertility and grain yield of the tested heat susceptible variety, and noninvasive anthers and pollen formation in response to HT were associated with improved heat tolerance.

Effect of Indigenous Bee Attractants on Qualitative and Quantitative Parameters of Egyptian Clover, Trifolium alexandrinum L.

Background: Egyptian clover (Trifolium alexandrinum L.) is one of the most important annual, winter, multi-cut fodder legumes grown in northern India. Many a times, poor activity of pollinators cited for lower seed production in berseem. Therefore, an appropriate local food-based bee attractants need to be identified and their effectiveness in enhancing berseem seed yield needs to be assessed. Methods: The experiment was conducted to evaluate the significance of bee visit on yield parameters of berseem. In addition, the effect of attractant (jaggery and sugar at 10%) in enticing honey bees towards the berseem flower was evaluated at ICAR- IGFRI, Jhansi during 2017 and 2018. Result: Both the attractants (jaggery and sugar at 10%) are equally effective in drawing the Apis dorsata towards berseem and higher bee visits (8.75 and 8.54/m2/5 min) were recorded one hour after application. Maximum seed setting percentage was recorded in plots sprayed with jaggery (83.53) followed by sugar solution (82.58), which is significantly superior over farmers practice i.e. crop left for open pollination (74.86). Maximum seed yield was obtained from plots sprayed with jaggery solution (8.15 q/ ha). The bee visit had significant positive effect on seed yield (0.685*) and 1000 seed weight (0.671*).