Number Of Reproductive Tillers Research Articles

Path Coefficient Correlation and Genetic Divergence in Bread Wheat (Triticum aestivum L.)

Genetic variation, heritability, genetic advance, correlation coefficient, path coefficient analysis and genetic divergence studied in wheat during rabi 2015-16 at oilseed farm of Chandra Shekhar Azad University of Agriculture &Technology, Kanpur (U.P). A collection of fifty wheat genotypes from different eco-geographic origin were evaluated for ten quantitative characters viz. days to 50 % flowering, days to reproductive phase, days to maturity, plant height (cm), number of reproductive tillers per plant, spike length (cm), number of grains per spike, grain weight per spike (gm.), test weight (gm.) and grain yield per plant (gm.).All the characters, under study showed considerable amount of variability, phenotypic coefficient of variability was higher than genotypic coefficient of variability.These traits exhibited higher variation for GCV and PCV across the environments. A persual of coeffiecient of variability indicates that PCV and GCV were quiet high for grain yield per plant. Moderate PCV and GCV were recorded in spike length and grain weight per spike and the lowest observed in days to maturityand days to 50% flowering. A high estimate of heritability was found for grain yield per plant. Genetic advance confirms the heritability estimate. High genetic advance was observed for grain yield (30.16) and minimum in days to reproductive phase (2.27). Genotypic correlation coefficients were higher than the corresponding phenotypic correlation coefficients for all the character combinations. Grain yield per plant showed highly positive association ship with plant height, spike length, grain weight per spike and number of grains per spike grain weight per spike. Genetic divergence was determined using D2 and all the fifty genotypes were grouped into eight clusters. Maximum inter cluster distances were observed betweenVI and VIII followed by cluster VII and VIII and cluster V and VIII. Cluster VII retains highest rank in spike length and grains per spike. Cluster-V holds first rank in days to flowering and days to maturity.On the basis of genetic divergence , it is suggested that the crosses between VIII ,VII , VI and V may be effective components in hybridization.

Hybrid purity identification using EST-SSR markers and heterosis analysis of quantitative traits of Russian wildrye.

Russian wildrye, Psathyrostachys junceus (Fisch.) Nevski, is widely distributed in the high latitude areas of Eurasia. It plays an important role in grassland ecosystem maintenance, as well as being a valuable palatable forage species for livestock and wildlife. Russian wildrye germplasm has rich phenotypic and genetic diversity and has potential for improvement through crossbreeding. In this study, fifteen Russian wildrye hybrid combinations were produced and one F1 population with 123 putative hybrids was obtained by crossing two individual plants with significant differences in nutritional characteristics and reproductive tiller number. Twelve phenotypic traits of the F1 population were measured for three consecutive years, and ten of the twelve traits were in line with the genetic characteristics of quantitative traits. Hybrid superiority was revealed among F1 hybrids in both nutritional and reproductive traits. One non-recurrent parent plant with the highest PCA-synthesis score was selected and used to make a backcross with the 'BOZOISKY SELECT' male parent, and 143 putative BC1 hybrids were obtained. Sixteen pairs of EST-SSR primers were randomly selected from polymorphic primers derived from different expressed tiller trait related genes. Three primer pairs that amplified both the paternal and maternal characteristic band were used to assess the purity of the F1 population, and three primer pairs (with one shared primer pair) were used to identify the BC1 population. The hybrid purity was 96.75% for the F1 population and 95.80% for the BC1 population, and the results were confirmed by self-fertility test through bagging isolation. The genetic similarity coefficients between the F1 progeny and the male parent ranged from 0.500 to 0.895, and those between the BC1 progeny and the male parent ranged from 0.667 to 0.939. A subset of individuals in the BC1 population had closer genetic distance to the recurrent parent, and genetic variation within the BC1 population decreased compared to the F1 population.

Efficacy of indigenous Trichoderma isolates of West Timor, Indonesia, as biocontrol agents of brown spot (Drechslera oryzae) on two upland rice varieties

BackgroundBrown spot disease is one of the most destructive foliar diseases of rice. Biological control of this disease is considered more environmentally safe, but the biological control agents have limited availability. The fungus Trichoderma can be used as a biocontrol agent for various plant diseases, including brown spots. Indigenous Trichoderma species from West Timor were evaluated in this study to reveal their effectiveness in reducing brown spot disease of upland rice. The study was conducted under a screen house condition using a factorial treatment design laid out in a completely randomized design. The two factors were the brown spot disease control method (T. viride, T. harzianum, T. hamatum, fungicide Trivia 73 WP, and a control treatment) and upland rice genotype (Inpago 7 and Breun Senaren 2).ResultsThe results showed that Trichoderma spp. and the fungicide Trivia 73 WP caused significantly lower AUDPC and apparent infection rate than the control treatment. The total phenol content and agronomic characters (number of reproductive tillers per plant, number of filled grains per panicle, grain yield per plant) were higher in the Trichoderma and fungicide treatments than the control treatment. Meanwhile, tannin and saponin levels were non-significantly different among treatments. Trichoderma and the fungicide Trivia treatments effectively suppressed brown spot disease of upland rice, and the efficacy was dependent on the rice variety, with a mean efficacy range over the two varieties of 27.05–36.42%. The Trichoderma and the fungicide Trivia treatments increased the grain yield per plant differentially in the 2 rice varieties, with a mean grain yield increase over the 2 varieties of 13.0% (T. viride), 23.5% (T. harzianum), 35.0% (T. hamatum), and 19.9% (Trivia 73 WP).ConclusionEfficacy of local Trichoderma of West Timor and the fungicide Trivia treatments were varietal dependent with T. hamatum being the most effective in reducing the brown spot disease and producing the highest grain yield increase over the 2 rice varieties. The local Trichoderma species of West Timor have a future potential as biocontrol agents of upland rice brown spot disease, but it is necessary to further evaluate their effectiveness against the disease in replicated field trials.

Management Systems for Biannual Seed Crop of Italian Ryegrass (Lolium multiflorum Lam.) Grown at Various Nitrogen Fertilization: II. Second-Production Year Characterized by Considerable Crop Lodging and Limited Seed Shattering before Direct Combine-Harvesting

Multiyear production of Italian ryegrass seed crop is of interest. The impact of management systems on the second-production year of biannual crop was evaluated at various nitrogen fertilization (0, 60, 120, and 180 kg ha−1). Management systems of single-purpose crops were with (SeedPGR-crop) and without (Seed-crop) plant growth regulator (PGR) application. The dual-purpose crops incorporated early (EF-seed-crop) and late (LF-seed-crop) spring forage cut followed by seed harvest. The Seed-crop obtained a maximum yield (1631 kg ha−1) at 120 kg N ha−1, which decreased by 23% at the highest fertilization. This yield loss was associated with early (before heading) and severe lodging that brought about reduced aboveground biomass and lower harvest index due to the increased growth of vegetative tillers. The single-purpose crops had a similar number of reproductive tillers, seed weight, and seed shed; however, the SeedPGR-crops produced larger yields than the Seed-crops at all fertilization levels indicating the positive impact of PGR application on harvest index regardless of lodging intensity. Despite less lodging and lower seed shattering, the dual-purpose crops yielded less than the single-purpose crops primarily due to the reduction in the number of spikelets per ear and florets per spikelet in various ear sections of early- and late-formed ears. Seed yields of the dual-purpose crops were maximized (around 1200 kg ha−1) at 180 kg N ha−1. The LF-seed-crop had the lightest seeds and the smallest seed germination, but fertilization tended to improve these quality traits. The SeedPGR-crop was the best performing management system yielding above 2200 kg ha−1 at the two highest N levels, allowing greater flexibility in fertilization.

The sward height at the early stockpiling period modifies the structural characteristics of marandu palisadegrass under continuous stocking

The control of sward height at the early stockpiling period influences the structural characteristics of stockpiled sward in winter. So, we conducted this work on the Cerrado region of Brazil based on the hypothesis that the reduction of pasture height at the beginning of stockpiling period results in: (i) lower stock of forage mass; and (ii) higher live leaf mass, but lower stem mass in stockpiled pasture during the winter. The treatments were four sward heights (15, 25, 35, and 45 cm) at early stockpiling period of marandu palisadegrass (Brachiaria brizantha syn. Urochloa brizantha cv. Marandu). The experiment was conducted in a completely randomized design, with three replications (paddocks with 800 m²). The stockpiled swards were evaluated during the grazing period in winter on days 7 (beginning), 45 (middle) and 90 (end). The vegetative tiller number (VEGT), live leaf mass (LLM) and leaf area index (LAI) were greater in the 15 cm stockpiled pasture than the other treatments. Greater heights (35 and 45 cm) at stockpiling resulted in greater forage mass than lower heights (15 and 25 cm). The VEGT, LLM, number of reproductive tillers, live stem mass, forage mass and LAI values were higher at the beginning than at the end of the grazing period. Our hypothesis has been proven, so that the reduction of sward height of the marandu palisadegrass at the beginning of the stockpiling period results in lesser forage mass, but with better structural characteristics.

Fire stimulates grass flowering in the Cerrado independent of season

AbstractQuestionsPost‐fire flowering is an underestimated plant trait of many fire‐prone ecosystems and is rarely considered for tropical savannas. Therefore, we analyzed the effects of fire season and history on post‐fire flowering of grass species in a tropical savanna (Cerrado), by evaluating the number of species, frequency of individuals and number of reproductive tillers after wet‐ and dry‐season fires, and under different fire histories.LocationsOpen savannas (campo sujo) of the Cerrado in central Brazil (Reserva Natural Serra do Tombador [RNST], 13°35–13°38′ S, 47°45′–47°51′ W).MethodsWe sampled flowering individuals in 10 Poaceae species and counted flowering/vegetative tillers of grass species in 1 m × 1 m plots after wet‐ and dry‐season fires and under different fire histories (3, 18 and 72 months post fire).ResultsSome of the studied species responded differently to fire according to season but most flowered after fire events. Moreover, the exclusion of fire led to a decrease in the number of flowering individuals and reproductive tillers of grass species.ConclusionsWe describe a unique event for tropical savannas: beside rapid resprout after fire events, grasses can allocate resources for both vegetative and reproductive tiller production, even during the dry season. If fire is excluded from the system, fewer grass species and individuals will flower and there will be a lower percentage of reproductive tillers, showing the importance of fire for grass flowering in these tropical savannas, independently of fire season.

EVALUATION OF SEVERAL WHEAT CULTIVARS IN RESPOND TO DIFFERENT TYPES OF FERTILIZERS INCLUDING BIO-FERTILIZER UNDER RAINFED CONDITIONS

The research was conducted during 2018-2019 growing season to study the growth and yield of various wheat cultivars under various methods of fertilizers application including bio-fertilizer under rainfed conditions of two different isohyets conditions. Randomized complete block design was applied with four replications. Potential grain yield is highly affected by the number of reproductive tillers; differences in final grain yield were highly and positively correlated to the number of tillers (r= 0.54**) and above ground biomass (r= 0.68**). The grain yield was about three times higher in Rikava location (3.19/1.01 t.ha-1). Both of Cihan and Adana99 wheat significantly produced higher grain yield (2.44 and 2.43 t.ha-1 respectively) followed by Tammoze and Italy, the Criso durum wheat was the inferior with only 1.65 t.ha-1 grain yield. DAP fertilizer (2.58 t.ha-1) was the best fertilizer treatment followed by YARA and BIO and all treatments were significantly higher than the check unit which produced only 1.7 t.ha-1. The interaction of Adana99 with DAP (2.79 t.ha-1) and Cihan with DAP (2.71 t.ha-1) recorded highest grain yield; these two cultivars with BIO fertilizer produced significant grain yield and each gave (2.5 t.ha-1). Financial analysis revealed the superiority of both Anana99 and Cihan cultivars with DAP fertilizer followed by BIO fertilizer as they contributed positively with the highest final revenue.

Does the lowering strategy before the stockpiling period modify the marandu palisade grass production and structure?

ABSTRACT The objective was to identify lowering strategies for Urochloa brizantha cv. Marandu in the beginning of the stockpiling period that increase forage production and improve the structure of stockpiled canopies. Three lowering strategies were evaluated: maintenance of marandu palisade grass with 15cm four months before the stockpiling period; maintenance of palisade grass with 30cm for four months, and lowering to 15cm before the stockpiling period; and maintaining of palisade grass at 45cm for four months, and lowering to 15cm before the stockpiling period. The experimental design was completely randomized, with four replications. At the end of stockpiling, the number of reproductive tillers and forage mass were higher in the canopy under 15/15cm than in the others; the percentage of live leaf was higher in the canopy under 45/15cm than under 15/15cm. Forage production during the stockpiling period was higher in the canopy under 15/15cm and lower in the under 45/15cm. Maintaining 15cm marandu palisadegrass for four months before the stockpiling period increases forage production during this period. The lowering of the marandu palisadegrass from 45 to 15cm at the beginning of the stockpiling period improves the structure of the stockpiled canopy.

PERFORMANCE ASSESSMENT OF CROSSES BETWEEN GADAM AND HARDCORE TANNIN SORGHUM IN HYBRID LINES PRODUCTION

Gadam cultivar of sorghum has been characterized by low yields compared to the international yield levels of sorghum. In this research, Gadam was crossed with Serena, Seredo, and Kari/Mtama-1 in an attempt to increase yield through heterosis. The objective of this study was to determine the level of compatibility and heterosis in crosses between Gadam and the three sorghum lines in a reciprocal crossing. Gadam was crossed with the three lines and their reciprocals to make six treatments that were subjected to compatibility and heterosis tests. The F1 hybrid lines and their parental controls were sown in a randomized complete block design in three replicates. Compatibility and heterosis data variances were analyzed using R statistical software. The cross between Gadam x Serena, Serena x Gadam and the parent Gadam exhibited moderate mean plant height ranging from 99.5 cm to 120.5 cm. The cross Gadam x Serena recorded a desirable negative mid-parent heterosis of -19.89 and -16.16 for plant height and days to maturity respectively. All F1 hybrids recorded positive mid-parent heterosis for the panicle length, the number of reproductive tillers, a thousand seed weight, and the number of tillers per plant. The crosses Gadam x Seredo, Seredo x Gadam, Gadam x Serena and Kari/Mtama-1 x Gadam recorded significantly lower grain filling percentages compared to their parents. In conclusion, the F1 hybrids differed significantly from their reciprocal crosses especially in days of heading, flowering, and maturity indicating a significant maternal influence in these traits. Also, the mid-parent and better parent heterosis had a nonsignificant difference in quantitative traits assessed except for the plant height and grain filling percentage.

Floret site utilization and reproductive tiller number are primary components of grain yield in intermediate wheatgrass spaced plants

AbstractPerennial plants provide extensive environmental services and increasing their prevalence on the agricultural landscape is one way to improve sustainability. Direct domestication of intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] as a perennial grain crop is underway, and selection has focused primarily on improving seed size and grain yield. Breeders lack understanding of grain yield and its relationship with component traits in this species. We characterized a large (n = 1,168) spaced plant nursery in St. Paul, MN, and Salina, KS, in 2017 and 2018 for a series of 13 yield component traits. In Year 2 in St. Paul, yield per plant and reproductive tiller number nearly doubled, whereas other yield components, including yield per spike, spikelets per spike, florets per spikelet, and thousand‐grain weight, significantly decreased. Correlation analyses between traits highlighted positive associations of seven traits with grain yield. Structural equation modeling (SEM) revealed that when yield was measured on a yield per spike basis, floret site utilization was the primary contributor to yield, and when measured on a per‐plant basis, reproductive tiller number was the primary contributor. The indirect effects of biomass and maturity traits on both measures of yield were limited. Future work should investigate the predictive ability of reproductive tiller counts in spaced plant and sward environments to inform how breeders assess and select for yield.

Herbage accumulation and canopy structure during stockpiling of Marandu, Piatã, Xaraés, and Paiaguás brachiariagrass cultivars

Abstract: The objective of this work was to compare herbage accumulation and canopy structural characteristics during the stockpiling period of the Marandu, Piatã, Xaraés, and Paiaguás cultivars of Urochloa brizantha. The experimental design was completely randomized, with three replicates. The experiment was repeated for two years (2017 and 2018), under mechanical cutting conditions, and the canopies were stockpiled for 90 days, from March to June. In the first year, forage mass was higher for the Xaraés and Paiaguás cultivars; however, in the second year, Xaraés showed a forage mass higher than that of the other cultivars. The number of vegetative tillers at the end of the stockpiling period was higher for Paiaguás, contrary to what was observed for number of reproductive tillers. The herbage accumulation rate was higher for the Paiaguás and Xaraés cultivars. The Paiaguás grass stands out for its high herbage accumulation rate during the stockpiling period and for its higher number of vegetative tillers and lower number of reproductive tillers than that of the other cultivars.

Identifying morphological traits associated with vegetative persistence in the perennial ryegrass (Lolium perenne L.) cultivar 'Grasslands Samson'

Perennial ryegrass (Lolium perenne L.) vegetative persistence (maintained herbage growth and survival without reseeding) is an important economic trait for farmers in New Zealand as it decreases the frequency of reseeding pastures. Vegetative persistence is difficult to breed for due to a lack of long-term trials to observe the complex interactions between plant genotype and the environment. In a long-term trial a genetic shift in the sown cultivar population could occur as individual plants with advantageous traits outcompete other plants and survive. The objectives of our study were to investigate the occurrence of a potential genetic shift in a sample (30 plants) of a persistent population of ‘Grasslands Samson’ perennial ryegrass. Persistent plants were collected from a nine-year-old trial at Poukawa, Hawke's Bay. To identify a genetic shift, these plants were compared to a sample of 30 plants sourced from commercial seed of ‘Grasslands Samson’ representing the original population. This study estimated genotypic variation within and between the populations for eight morphological traits after 10 weeks' growth under glasshouse conditions. Phenotypic and genotypic correlations between the traits were estimated. Results showed that the persistent population had significantly (P<0.05) greater means for tiller number, reproductive tiller number, lamina sheath length, and dry weight. Future research studying these traits across farm environments would further understanding of their roles in vegetative persistence of ryegrass.

Life history traits of an Echinochloa crus-galli var. crus-galli population with extreme adaptations to rice planting systems

Long-term herbicide application may facilitate the adaptive evolution of weed populations. With Echinochloa crus-galli var. crus-galli population A from a rice field used for the experiment of effectiveness of herbicide in Nanling County, Anhui Province, we conducted common garden experi-ments with seeds of population A and three control populations collected from normal rice fields. Compared with the three control populations, population A had significantly lower seed production for individual plant, but higher 1000-seed weight. Population A had faster in seedling growth, higher in number of reproductive tillers, shorter life span, lower in height and biomass of individual plant, as well as lower in sensitivity to herbicide penoxsulam. Individuals from population A survived from 2× label dose (60 g·hm-2) of penoxsulam treatment at the three- to four-leaf stage showed significantly reduction in plant height, biomass, and mature seed production (1066 seeds per plant), but no difference in heading period, number of reproductive tillers, number of seeds per raceme and 1000-seed weight. The short lifespan, heavy seeds, dwarf architecture, more reproductive tillers and penoxsulam resistance made E. crus-galli var. crus-galli population A extremely adapting to rice planting systems, which should be prevented to spread to normal rice fields.

Effects of spacing and water control on growth and yield performance of irrigated rice in Guinea savannah Agro-ecological zone

The adoption of some attributes of the system of rice intensification (SRI) like water control and planting distance may help improve the productivity of rice. The aim of this study was to use water supply and plant density, components of SRI, to improve rice yield and reduce water use. The study was conducted at Golinga irrigation scheme. Continuous and Intermittent flooding served as main plots in a split-plot design. Four plant spacing, 20 x 20, 25 x 25, 30 x 30 and 40 x 40 cm, were used as subplot treatments. Water control and planting distance interaction significantly (P=0.001) influenced plant height where intermittent flooding promoted taller plants in narrow and wider planting distance (20 x 20 cm and 40 x 40 cm). Days to 50% flowering lengthened with increasing planting distance. Tiller and reproductive tiller number per plant were influenced by only planting distance (P=0.001) and the numbers increased with increasing planting distance. Dry root weight was significantly influenced by both water control (P=0.001) and planting distance (P=0.001). Intermittent flooding induced better root development. (0.678 kg/hill) than continuously flooding (0.598 kg/hill). Root development also improved with increasing planting distance, from 0.37-0.90 kg/hill. Panicle number per unit area, paddy grain yield and straw weight were significantly influenced (P=0.001) by planting distance with 25 x 25 cm giving the best performance. Paddy yield of 5.2 ton/ha at a planting distance of 25 x 25 cm was above the national average and within the potential yield of the variety. It can be concluded that intermittent and continuous flooding gave a similar performance. Increasing plant spacing helps to improve individual hill performance but beyond 25 x 25 cm planting distance, the benefits at the individual hill performance are offset by reduced plant density. 

Coupled influence of precipitation regimes and seedling emergence time on the reproductive strategy in Chloris virgata.

Precipitation regime and seedling emergence time both influence plant growth and reproduction. However, little attention has been given to the effects of these combined factors on the reproductive strategy of Chloris virgata, which is a vital species in Songnen grassland. Here, we simulated the changes in the precipitation regime and seedling emergence time to evaluate tiller traits and seed production. The results showed that tiller number behaved similarly among three precipitation regimes when sowed on 15 May (T1), while it increased significantly with precipitation regimes when sowed on 15 June (T2) and 15 July (T3). Tiller number decreased significantly with the seedling emergence time under the same water supply treatment. The proportional allocation of reproductive tiller number to total tiller number was significantly higher at T3 than at T1 and T2. Seed number remained similar under different precipitation regimes at T2 and T3, whereas it was significantly lower under low precipitation than under other water levels at T1. Seed number reached the maximum values at T2 under the same level of precipitation treatment. Seed size was significantly lower under low precipitation compared to other water supply treatments and the lowest values in seed size, about 0.5 mg, occurred at T2 under all the precipitation regimes. The lowest values in spike number were under low precipitation at all seedling emergence times. Seed yield exhibited similar trends with seed size under different precipitation regimes, while the greatest gains in these values were at T1 under all the precipitation regimes. Our findings showed that simulated precipitation regimes and seedling emergence time affected the reproductive strategy of C. virgata. Typical and high precipitation, as well as early seedling emergence, will improve the seed yield and seed quality in this species.

Heat stress responses in a large set of winter wheat cultivars (Triticum aestivum L.) depend on the timing and duration of stress.

The adverse effects of heat on plant yield strongly depend on its duration and the phenological stage of the crops when the heat occurs. To clarify the effects of these two aspects of heat stress, systematic research was conducted under controlled conditions on 101 wheat cultivars of various geographic origin. Different durations of heat stress (5, 10 and 15 days) were applied starting from three developmental stages (ZD49: booting stage, ZD59: heading, ZD72: 6th day after heading). Various morphological, yield-related traits and physiological parameters were measured to determine the stress response patterns of the wheat genotypes under combinations of the duration and the timing of heat stress. Phenological timing significantly influenced the thousand-kernel weight and reproductive tiller number. The duration of heat stress was the most significant component in determining both seed number and seed weight, as well as the grain yield consequently, explaining 51.6% of its phenotypic variance. Irrespective of the developmental phase, the yield-related traits gradually deteriorated over time, and even a 5-day heat stress was sufficient to cause significant reductions. ZD59 was significantly more sensitive to heat than either ZD49 or ZD72. The photosynthetic activity of the flag leaf was mostly determined by heat stress duration. No significant associations were noted between physiological parameters and heat stress response as measured by grain yield. Significant differences were observed between the wheat genotypes in heat stress responses, which varied greatly with developmental phase. Based on the grain yield across developmental phases and heat stress treatments, eight major response groups of wheat genotypes could be identified, and among them, three clusters were the most heat-tolerant. These cultivars are currently included in crossing schemes, partially for the identification of the genetic determinants of heat stress response and partially for the development of new wheat varieties with better heat tolerance.

System of Rice Intensification Verses Conventional Rice System: Off-farm Field Studies

With inevitable growth of demand for human and industrial needs, water available for agriculture will become scarcer in the future. India is a highly water-stressed country. Hence, India needs to invest in improving its water productivity, and any capacity to produce more rice with less water. System of Rice Intensification (SRI) has attracted much attention in increasing rice yield per unit area. For this study, fifteen farmers were selected those were practicing SRI technology by themselves during the Boro-cultivation season (January-April). The study was continued for three consecutive years 2012 to 14 on the same fields. In addition to the SRI plots, a similar size of non-SRI plot was maintained in conventional cultivation for comparison purpose. On an average, the non-SRI ight increased by 12%, number of tillers per square meter by 85%, number of reproductive tillers per hill by 286%, weight of panicle per hill by 139%, number of seeds per panicle by 41% and test weight by 26% due to SRI practice over the non-SRI practice. Average increment in straw and grain yield due to SRI over the non-SRI is 70% and 59% respectively. The physico-chemical and biological properties of soil improved due to SRI practice.

Seed yield in perennial ryegrass (Lolium perenne L.): comparative importance of component traits and detection of seed-yield-related QTL

The aims of our study were to evaluate relationships amongst morphological traits associated with seed production in a perennial ryegrass biparental population and to identify genomic regions associated with phenotypic variation in those traits using QTL analysis. This was achieved using data from two field experiments at Palmerston North and Lincoln, New Zealand, in 2003, and days to heading (DTH), reassessed in 2004. Trait association was determined for the Palmerston North experiment where measured traits included seed yield per plant (SYPlant), seed yield per spike (SYSp), reproductive tiller number (RTiller), spikelets per spike (SpktSp), florets per spikelet (FSpkt), 1000 seed weight (TSW), spike length (SpLen), florets per spike (FSp), floret site utilization (FSUtil), spread of heading (SOH) and plant growth habit (PGHabit). Traits contributing to SYPlant in order of descending value were FSpkt, FSUtil, and RTiller. High TSW was only weakly linked to SYPlant. FSUtil, SOH and RTiller were identified as valuable breeding targets for improving seed yield potential in perennial ryegrass. QTL were identified for all traits except for RTiller. QTL for SYPlant occurred on linkage groups (LG) 2 and 6. Both were co-located with QTL for SYSp and sets of SYPlant components or related traits (FSpkt, FSp; FSUtil and TSW). Major QTL for DTH were identified on LG2 and LG4 and minor QTL on LG7 in consecutive years. There was a strong genotype-by-environment interaction for SYPlant that was reflected in a lack of consistent QTL across environments, while QTL for SYSp and DTH were stable across environments. Identification of component traits and QTL important for seed yield may accelerate genetic improvement in perennial ryegrass through conventional and marker-assisted breeding, respectively.

Can endosymbiotic microbes modulate natural selection in plant populations? An example with Lolium perenne and its fungal endophyte

Many plant species are symbiotic with systemic microbes. For example, many grasses are inhabited by fungal endophytes that affect aspects of their host’s physiology, morphology, and reproduction. However, there have not been any analyses of the potential effect of endophytes on the strength of phenotypic selection on quantitative traits. Here, a previously published data set on several life history traits measured for two years in a field population of 12–13 Lolium perenne genotypes, each replicated as symbiotic and non-symbiotic plants, was analyzed using the standard Lande-Arnold method of selection analysis. In one year, endophytic symbionts reduced the strength of selection on the number of reproductive tillers when relative fitness was expressed as seed yield. Also, symbionts selected for reduced tiller production when fitness was expressed as mean seed mass. These changes in the strength of selection only occurred when fitness of genotypes when symbiotic was unrelated to fitness of the same genotypes when non-symbiotic. In a second year, when fitness of symbiotic and non-symbiotic groups were significantly correlated, there was no detectable selection on reproductive tiller production. Because the effects of microbial endosymbionts were only shown for one year in a single host population, additional research is needed to better assess how endosymbionts might mediate selective pressures in other natural plant populations.

Impact of Elevated CO<sub>2</sub> on <i>Oryza sativa</i> Phenology and Brown Planthopper, <i>Nilaparvata lugens</i> (Hemiptera:Delphacidae) Population

The impact of elevated CO 2 (570 ± 25 ppm) on brown planthopper, Nilaparvata lugens (Stal) and Pusa Basmati 1401 rice in comparison to ambient CO 2 was studied in open top chambers (OTCs) during the rainy seasons of 2013 and 2014. Crop canopy circumference was higher (13.1–16.8 cm) under elevated CO 2 when compared to ambient CO 2 (10.3–13.1 cm) during different rice phenological stages indicating the positive influence of elevated CO 2 . In addition, elevated CO 2 exhibited a positive effect on rice plants through increase in tiller number (17.6%), reproductive tiller number (16.2%), number of seeds/panicle (15.1%) and thousand grains weight (10.8%) that resulted in higher grain yield (15%) when compared to ambient CO 2 . Elevated CO 2 also exhibited a positive effect on brown planthopper population through increase in fecundity (29% and 31.6%) which resulted in a significant increase in its population to 150.3 ± 16.4 and 97.7 ± 8.7 hoppers/hill at peak incidence during 2013 and 2014 respectively, when compared to the corresponding 49.1 ± 9.3 and 43.7 ± 7.0 hoppers/hill under ambient CO 2 . Moreover, brown planthopper females excreted more honeydew (68.2% and 72.3%) under elevated CO 2 over ambient CO 2 during both years. However, elevated CO 2 caused reduction in the longevity of females (23.9–27.4%) during both years and male longevity (24.1%) during 2013. Despite the positive effect, rice crops suffered higher yield loss under elevated CO 2 (29.9–34.9%) due to increased brown planthopper infestation coupled with higher sucking rate due to reduced nitrogen level under elevated CO 2 compared to ambient CO 2 (17–23.1%) during 2013 and 2014.