Path analysis for grain yield and its components in rice

Rice yield, its components and their relations are one of the most important research objects for genetics, cultivation, and breeding. This study was to investigate the genetic relationships between yield and yield components by using the methods of correlation analysis and path analysis with a set of 241 RIL population of Shanyou 63.     

Seeding date influence on camelina seed yield, yield components, and oil content in Chile

Camelina (Camelina sativa L.) was introduced for the first time in Chile in 2008 as a potential feedstock for biodiesel and also as high omega-3-containing seed oil for the salmon feed industry. The objective of this study was to determine the optimum seeding date to maximize camelina seed yield in South Central Chile. The experiment was conducted under dryland conditions in Chillán, El Carmen, Los Angeles, Gorbea, and Osorno in 2008 and in Chillán and Los Angeles in 2009. The experimental design was a RCB with a split-plot arrangement with four replicates, where the main plot was the seeding date (five dates) and the sub-plot the spring type cultivars (Gold of Pleasure, Suneson, and Blaine Creek). Seeding dates at each environment were targeted to 30 April, 15 May, 30 May, 30 June, and 30 July of 2008 and 2009. The combined analysis of variance indicated no cultivar main effect or interactions with cultivar. The date by environment interaction was significant for seed yield. There were no seed yield differences among seeding dates in Chillán and El Carmen. The first three seeding dates were the highest yielding in Los Angeles and Osorno, and only the first seeding date was significantly higher in seed yield in Gorbea. Highest seed yield at Los Angeles, Gorbea, and Osorno were 1995, 1310, and 2314 kg ha⁻¹. Seed oil content was not different among seeding dates in Chillán and El Carmen. Highest seed oil content occurred at Osorno and Gorbea on the first three seeding dates and ranged from 420 to 457 g kg⁻¹. Spring camelina cultivars are well adapted to South Central Chile as a winter annual crop when seeded before 15 May except in Osorno when seeded before 30 May. No disease or insectpests were observed except for Aster Yellow infestation at Chillán and Los Angeles. Camelina has great potential as an oilseed for biodiesel and as a source of omega-3 for the pharmaceutical industry but markets for it need to be developed locally for camelina to become an option for growers.     

Combining ability analysis for Phaeosphaeria leaf spot resistance and grain yield in tropical advanced maize inbred lines

Phaeosphaeria leaf spot (PLS) disease (causal agent Phaeosphaeria maydis (Henn.) Rane, Payak & Renfro) of maize is increasing in importance in sub-Saharan Africa (SSA). However, there is still limited information on the combining ability for disease resistance of the germplasm that are adapted to African environments. Evaluating combining ability effects and their interactions with the environment would provide valuable information that can be used in the development of cultivars that are resistant to PLS. This study was therefore conducted to determine the combining ability, gene action and the relationship between grain yield and PLS disease severity among selected tropical advanced maize inbred lines. Forty five F₁ hybrids were generated by crossing 10 inbred lines in a half diallel mating scheme. The 45 hybrids along with the ten inbred parents were evaluated in four environments, with two replications each between 2007 and 2009. General and specific combining ability (GCA and SCA) effects were highly significant (P ≤ 0.001) for PLS, grain yield and days to anthesis. GCA effects accounted for 66–90% and SCA effects for 10–34% of the variation in the hybrids for PLS resistance, grain yield and days to anthesis. This indicated predominance of additive over non-additive gene action for the three traits in these inbred lines. The resistant inbred lines to PLS were A1220-4, N3-2-3-3, CML312, MP18 and CML488. These lines had good combining ability for PLS resistance and contributed towards resistance in their crosses. In general, resistant hybrids involved a susceptible and a resistant parent, where at least one of the parents had a negative GCA effect. In addition, lines A1220-4 and CML312 contributed towards high yield and were late maturing. Inbred line CZL00009 conferred genes for early maturity. Linear regression analysis indicated that grain yield of maize was suppressed by about 250 kg ha⁻¹ per each increase in PLS disease severity score, underscoring the need to control the disease. Significant (P < 0.01), negative correlations (r = −0.29 to −0.43) between grain yield and PLS severity were also detected. This showed the potential of PLS to reduce yield when favourable conditions for disease development are present. By and large, highly significant additive gene action implied that progress would be made through selection. Although non-additive effects were small (±10%), observation of dominance effects which were associated with reduced disease levels in some hybrids may be exploited in developing single cross maize hybrids among these inbreds when one parent is resistant.     

Combining ability and heterosis of sorghum germplasm for stem sugar traits under off-season conditions in tropical lowland environments

Bioethanol production from sweet sorghum entails expansion and intensive production of the crop, which may include off-season production in the warm tropical lowlands. However, suitable cultivars are currently not available for this environment, especially in southern Africa. Hybrid cultivars were long ago demonstrated to be more productive than pure line varieties. Therefore a study was conducted to determine heterosis of experimental hybrids, and combining ability of parental lines for stem sugar traits. Sixty-four hybrids were generated among 16 lines in accordance with North Carolina design II mating scheme. Eight parents were cytoplasmic male sterile lines which were designated as females and were crossed with eight male fertile lines. The hybrids were evaluated at two sites in Mozambique and South Africa under off-season production conditions. Row-column alpha designs with three replications were used and standard agronomic practices were followed at both sites. Data were analysed in GenStat computer package. There was significant (P = 0.05) variation among genotypes for stem °brix and associated traits. The top 20 stem °brix performers were constituted by 17 hybrids, exhibiting heterosis of up to 112%, and three parents. General and specific combining ability effects were significant for stem °brix and associated traits implying that both additive and non-additive gene action, respectively, were important for controlling the traits. The lines ZLR1 and ICSVP3046 displayed significant and positive GCA effects for stem °brix, while 13 crosses showed positive and significant SCA effects. These lines and the crosses ISCVP3046 × ICSA4, ICSV700 × ICSA731, ICSR165 × ICSA307, ZLR1 × ICSA474 and ICSR57 × ICSA479, which combined high mean performance with positive SCA effects, would be recommended for use in breeding new varieties for tropical lowland environments.     

Combining ability for yield,protein, lysine and tryptophan in pearl millet (Pennisetum americanum L.)

Estimates of general and specific combining ability for grain yield, protein, lysine and tryptophan levels in the grain were obtained by evaluating the performance of 150 F₁ pearl millet hybrids which were derived by crossing 5 male-sterile lines to 30 geographically diverse testers. Significant differences were found for grain yield and protein in males and for protein and tryptophan in females. The variation due to male × female interaction was significant for all the characters.The additive as well as non-additive genetic variance played an important role in the expression of these characters but the magnitude of the non-additive component was substantially higher. The specific combining ability effects of certain crosses were related to the general combining ability effects of their parents and there was some degree of relationship between heterobeltiosis and specific combining ability effects.Percentage protein was negatively correlated with yield, lysine and tryptophan among hybrid population. The positive association between lysine and tryptophan offers scope for improving protein quality with simultaneous increase in yield. The parents KG-70-2, Madras 34, I.B. (64-1-SPS) and MPP 7105 have potential for exploitation in future breeding programmes.     

Image analysis and histochemistry to identify mobile stem resources for seed production in soybean

Resources for soybean [Glycine max (L.) Merr] pods are supplied initially from newly assimilated chemicals. As reproduction progresses, dependence on stored reserves increases. Seed weight is sensitive to stored shoot reserves, but the role of stem resources in late seed filling is unclear. Pith and cortex tissues contain living cells in stems and play a key role in storage. We hypothesized that main stem tissue composition can predict concentrations of mobilizable resources, which can be used to calculate impacts of mobilizable chemicals on yield. A field experiment with determinate cultivars investigated stem tissue composition, mobile and immobile chemicals, and their relationship with fruit production. Pith was correlated with non-structural chemicals; xylem and phloem predicted structural chemicals. During late seed filling, mobile stem chemicals decreased 67.5%, and we found a negative relationship between pith and aborted pods. Results support our hypotheses and highlight the importance of pith in remobilized resources for seed production in soybean.     

Estimation of combining ability for yield and yield components in rice (Oryza sativa L.) cultivars using diallel cross

In order to estimate combining ability and gene action of a number of rice cultivars, a 5 x 5 half a diallel cross genetic design has been used. Parents and their hybrids have been evaluated in a randomized complete block design with 3 replicates for yield and 6 yield components in 2007 in Rice Research Station of Iran-Amol. Mean squares of genotypes for all traits were highly significant (p < 0.01). Significant mean squares of combining ability for all traits showed additive and non-additive effects in control of the related traits. Having nonsignificant MS(GCA)/MS(SCA) ratio for all traits but 1000-grain weight show higher importance of nonadditive effects in comparison with additive effects of controlling genes. High relative importance of specific combining ability indicated that all traits but 1000-grain weight are highly affected by impacts of specific combining ability. Generally, Dasht, Neda and Binam were the best parents for general combining ability and Binam x IR62871-175-1-10 and Mashhad Domsiah x Binam were the best hybrids for grain yield and its components.     

Effects of planting system,plant density and flower removal on yield and quality of hybrid seed in cotton

Seedling transplanting and plastic mulching are widely adopted intensive planting systems in cotton production in China. Manual removal of early- or late-season flowers may improve seed quality without sacrificing yield through the compensatory growth of cotton plants. Two experiments were conducted, in Yellow River Valley in China from 2002 to 2003, to test if the intensive systems and flower removal can be used for enhancing hybrid seed production. Results in the first experiment show that yields of seed cotton and seed, and seed quality parameters averaged across three plant densities (2.25, 3.00 and 3.75 plants/m²), were significantly improved by either transplanting or plastic mulching relative to conventional planting. The improvements in yield and quality in two intensive planting systems were mainly attributed to longer and earlier flowering period. Transplanted plants did not differ significantly from mulched plants in seed yield, seed maturity and percentage germination, but transplanting decreased lint percentage and increased seed index relative to mulching. In terms of seed yield and quality, the optimum plant density for each planting system was 3.00 plants/m². At the optimum plant density, seed yields averaged across two years for transplanting and mulching systems were 31.3% and 32.6% higher than for conventional planting system, respectively. Flower removal did not significantly affect seed yield, but removal of late-season or both early- and late-season flowers significantly improved seed quality. It was concluded that transplanting or plastic mulching, low plant density (3.00 plants/m²), and removal of late-season or both early- and late-season flowers can be integrated to enhance yield and quality of hybrid seed of cotton.     

海滨锦葵生长发育、产量和产量构成对盐分胁迫的响应

研究了不同盐分浓度条件下海滨锦葵的生育特性、产量和产量构成。结果表明,海滨锦葵生育期约为139-165d,从播种到子叶展平需10-20d,现蕾出现在5月中旬至6月初,现花出现在6月中旬至7月上旬,盛花期出现在7月初至7月中下旬,果实成熟期出现在8月中旬至9月上旬。海滨锦葵生育期可划分为播种出苗期、苗期、蕾期、开花期和籽粒成熟期等5个阶段。不同盐分浓度条件下,海滨锦葵的生育进程存在明显差异,盐分浓度的提高使得营养生长期推迟,其次是生殖生长期。随着盐分浓度的增加,各生育时期的株高显著降低。各个生育时期海滨锦葵叶片的长度和宽度都受到盐分明显影响,长度和宽度均显著降低。盐分浓度低于0.3%及以下时,每株果枝数显著下降,每果枝粒数和百粒重与对照无显著差异,产量显著降低。0.6%浓度条件下尽管百粒重无显著差异,但果枝数显著增加和每果枝粒数显著下降,产量也显著降低。当盐分浓度增加到0.9%和1.2%时,果枝数、每果枝粒数和百粒重均显著下降,产量也显著降低。     

Combining ability and gene action studies for yield and fibre traits in Gossypium arboreum using Griffings numerical and Haymans graphical approach

Background For the purpose of utilising hybrid vigour to produce possible hybrids with a suitable level of stability, the knowledge of gene activity and combining ability is a crucial prerequisite before choosing desirable parents. The present study was carried out with six parents crossed in full diallel fashion and generated 30 F1 hybrids. These hybrids were evaluated in two replications in Randomized Block Design at Department of Cotton, TNAU for combining ability and gene action. Diallel ana...     

Breeding for drought tolerance: Direct selection for yield, response to selection and use of drought-tolerant donors in upland and lowland-adapted populations

Drought is the most important constraint reducing rice yield in rainfed areas. Earlier efforts to improve rice yield under drought mainly focused on improving secondary traits because the broad-sense heritability (H) of grain yield under drought stress was assumed to be low, however gains in yield by selecting for secondary traits have not been clearly demonstrated in rice. In present study, the effectiveness of direct selection for grain yield was assessed under lowland reproductive stage stress at Raipur in eastern India and under upland reproductive stage drought stress at IRRI. The selection under severe stress (in both upland and lowland trials) resulted in greater gains under similar stress levels (yield reduction of 65% or greater under stress) in evaluation experiments than did selection under non-stress conditions, with no yield reduction under non-stress conditions. We observed similar H of grain yield under stress and non-stress conditions, indicating direct selection for yield under drought will be effective under both lowland and upland drought stresses. None of the secondary traits (panicle exsertion, harvest index, leaf rolling, leaf drying) included in our study showed a higher estimate for H than grain yield under stress. Secondary traits as well as indirect selection for grain yield under non-stress situation were predicted to be less effective in improving yield under drought in both lowland and upland ecosystem than direct selection for grain yield under the respective stress situations. The low, but positive values observed for genetic correlation (r_G) between yield under stress and non-stress indicated that it is possible to combine drought tolerance with high-yield potential but low values also indicated that selection for grain yield needs to be carried under stress environments. The study also indicated that under lowland drought stress, the use of highly drought-tolerant donors, as parents in crosses to high yielding but susceptible varieties resulted in a much higher frequency of genotypes combining high-yield potential with tolerance than did crosses among elite lines with high-yield potential but poor tolerance. Breeding strategies that use drought-tolerant donors and that combine screening for yield under managed drought stress with screening for yield potential are likely to result in the development of improved cultivars for drought-prone rainfed rice producing areas.     

Association of growth dynamics, yield components and seed quality in long-term trials covering rapeseed cultivation history at high latitudes

Brassica oilseed yield trend has declined in Finland by over 20% during the last 15 years. Improved genetic yield potential of turnip rape (B. rapa L.) and oilseed rape (B. napus L.) can be better realised with increased understanding of yield determining processes under northernmost growing conditions. This study aimed at (1) determining the genetic improvements in seed yield, yield components, quality traits and duration of the main growth phases and (2) comparing all these traits in turnip rape and oilseed rape. This work is based on the dataset from long-term Official Variety Trials (1976–2006), covering the entire historically relevant period of rapeseed cultivation in Finland. The results indicated that number of seeds per square metre dominated production of high yields, while single seed weight was not correlated with yield. Over the years, seed yields were produced with very different combinations of seed numbers and weights, differing markedly between the two crops. While high seed numbers were required for production of superior seed yields, single seed weights were not particularly high. Environmental variation markedly affected seed yield, seed number per square metre and duration of flowering compared with its effect on single seed weight. Duration of flowering was, however, negatively associated with seed number. Even though seed weight was largely determined by genotype, no marked plant breeding improvements were identified, contrary to those in number of seeds per square metre, seed yield, oil content and oil yield. For oilseed rape the increase in seed yield (41%) was far higher than for turnip rape (19%) without being associated with a longer seed-filling phase and later ripening, but rather the contrary.     

Irrigated cotton in the tropical dry season. I: Yield,its components and crop development

Growing cotton during the dry (winter) season avoids many insect pests endemic in the wet season (summer) and could permit the reintroduction of cotton to the semi-arid tropics in Australia. This research addressed the questions: (1) what yield is possible given the lower mid-season radiation and temperature of the dry season, (2) the prediction and management of crop development using a range of sowing months to assess whether cotton can be grown and picked within the dry season. Over three seasons two Gossypium hirsutum L. (upland) cultivars and one Gossypium barbadense L. cultivar were sown from March, to June at the Ord River (15.5°S) in Western Australia. For the upland cultivars, lint yields of 1900–2300 kg/ha for March and April sowings were at the high end of Australian and International benchmarks. High lint yields were linearly correlated with a greater proportion of bolls that were located on outer sites on fruiting branches than for high yielding crops in temperate climates (∼30°lat.). The change in boll position increased the length of the growing season which was also linearly correlated with yield. Future research needs to confirm if low minimum temperatures early in flowering caused the change in boll position and to measure the impact of extreme temperature seasons on yield and time to maturity. The lint yield of the G. barbadense cultivar was highest at a March sowing, at least 87% of the upland cultivars, which is comparable with temperate climates. The frequency of temperatures >35 °C and <11 °C affected time to squaring, requiring modification of existing development models derived in temperate climates. It was concluded sowing during March to April should achieve the dual objectives of high yields and avoidance of rain at maturity. The wide temperature range observed in these experiments improved the prediction of boll period from mean temperature; this function should be applicable outside the semi-arid tropics.     

辽宁省北票市棉花高产高效轻简化栽培技术及应用

针对辽宁省北票市传统植棉用工多、劳动力不足、植棉成本高、机械化水平低的现状,提出采用以机械直播、化学除草、病虫防治、化学调控塑形、集中采摘为核心的高产高效轻简化栽培技术,可减少植棉的人工投入、提高机械化应用、节约劳动力和成本。该技术可为辽宁特早熟棉区棉花生产的恢复和可持续发展提供重要技术支撑。     

Effect of tolerance to Septoria tritici blotch on grain yield,yield components and grain quality in Argentinean wheat cultivars

Septoria tritici blotch (STB) caused by Zymoseptoria tritici (Mycosphaerella graminicola) is a major disease of wheat worldwide due to significant losses in grain yield and quality. Disease tolerance is the ability to maintain yield performance in the presence of disease symptoms. Therefore, it could be a useful tool in the management of the disease. Although it is known, that there is disease tolerance to STB in some wheat cultivars, this aspect has not been studied among Argentinean cultivars. The aims of this study were to evaluate genotypic differences in tolerance to STB among Argentinean cultivars, considering the relationship between the area under disease progress curve or the green leaf area or the non-green leaf area duration with the grain yield. In addition the effect of the disease on yield, yield components, test weight, grain protein concentration, wet and dry gluten concentration and the influence of tolerance on these traits was investigated. Field experiments were carried out with ten cultivars in a split-split-plot design during 2010 and 2011. Inoculation treatments were the main plots and cultivars, the subplots. STB significantly reduced grain yield, their components, test weight and increase grain protein and gluten concentration. Cultivar Baguette 10 showed major tolerance to STB, indicated by a consistent low regression slope between the green area duration and yield, while Klein Chaja was non-tolerant due to a high regression slope. However, many cultivars such as Buck Brasil, Buck 75 Aniversario, Klein Escorpion and Klein Flecha had considerably similar regression slopes to Baguette 10, provided good levels of tolerance. Other cultivars presented no significant differences. The correlation coefficient between tolerance and grain yield potential was not significant, suggesting that tolerant high-yielding cultivars can be obtained. No relationship was found between quality group or tolerance with the increase in protein and gluten concentration due to STB either.     

Growth,yield and fiber quality characteristics of Bt and non-Bt cotton cultivars in response to boron nutrition

Background Boron(B) deficiency is an important factor for poor seed cotton yield and fiber quality.However,it is often missing in the plant nutrition program,particularly in developing countries.The current study investigated B’s effect on growth,yield,and fiber quality of Bt(CIM-663) and non-Bt(Cyto-124) cotton cultivars.The experimental plan consisted of twelve treatments:Control(CK);B at 1 mg·kg^-1 soil application(SB1);2 mg·kg^-1 B(SB2);3 mg·kg^-1B(SB3);0.2% B f...     

Genetic analysis for resistance to bean fly (Ophiomyia phaseoli) and seed yield among common bean genotypes in a semi-arid environment

Bean fly (Ophiomyia spp.) is a major field pest limiting common bean production in eastern Africa. The genetic enhancement of beans for resistance to insect pests is essential for minimizing yield losses arising from crop damage. The objectives of this study were to (1) assess combining ability for bean fly resistance and seed yield accumulation in common bean and (2) estimate genetic parameters associated with resistance for formulating further breeding strategy. Four parents with known reaction to bean fly were crossed with four locally adapted genotypes in an 8 × 8 half diallel mating design. Parents and F₂ progenies were grown in an alpha-lattice design replicated twice in an open-field and subjected to natural populations of bean fly for two cropping seasons under semi-arid conditions. Similarly, two resistant and two susceptible parents were selected and crossed to produce populations for generation means and variances components analysis. Results revealed that both general combining ability (GCA) and specific combining ability (SCA) mean squares were significant (p ≤ 0.05) for all four traits studied except SCA for stem damage during one cropping season. Among the parents, GBK 047858 was the best general combiner for all the traits studied across seasons except for stem damage during long rains (LR) 2009. Besides, genotypes GBK 047821 and Kat × 69 (a locally adapted variety) were generally good general combiners for resistance traits as well as seed yield. General predictability ratio (GPR) values ranging from 0.63 to 0.90 were obtained for plant mortality, stem damage, pupae in stem and seed yield across cropping seasons. These results established the predominance of additive gene effects (fixable variation) over the non-additive effects in controlling the traits. Low to moderate narrow sense heritability values ranging from 0.22 to 0.45 were obtained for pupae in stem. Such heritability estimates indicate that although additive gene components were critical in the inheritance of resistance for the trait, non-additive gene action were also important in addition to the environmental effects.     

Variability of root length density and its contributions to seed yield in chickpea (Cicer arietinum L.) under terminal drought stress

The importance of root systems in acquiring water has long been recognized as crucial to cope with drought conditions. This investigation was conducted to: (i) evaluate the variability on root length density (RLD) of chickpea in the vegetative growth stage; (ii) estimate the effect of RLD on seed yield under terminal drought conditions; and (iii) set up a procedure to facilitate the screening of chickpea genotypes with large RLD. Twelve diverse chickpea genotypes were grown in tall PVC cylinders with two different soil water treatments in 2000 and 2001, and in field under water deficit conditions during 2000/2001 and 2001/2002. In field trials, the mean RLD at 35 days after sowing showed a significant positive correlation with seed yield in both years. Similarly, the RLD in the 15–30 cm soil depth had significant positive effects to the seed yield in both years. The importance of the root trait was particularly relevant in 2001/2002, a more severe drought year, when the RLD in deeper soil layer, 30–60 cm depth, showed a significant positive relationship with seed yield. Also, the RLD at deeper soil layer, 30–60 cm depth, was higher in 2001/2002 than in 2000/2001, in particular in tolerant genotypes. The PVC cylinder trials were set up to facilitate the screening of chickpea genotypes with large RLD. RLD of plants grown in cylinders with 70% field capacity was correlated with RLD in the field trials (r = 0.731; p = 0.01). This work highlights the importance of roots in coping with terminal drought in chickpea. The cylinder system offers a much easier procedure to screen chickpea genotypes with large RLD.     

Genetic resistance to and effect of leaf rust and powdery mildew on yield and its components in 50 soft red winter wheat cultivars

Effects of leaf rust (caused by Puccinia triticina f. sp. tritici Eriks.) and powdery mildew [caused by Blumeria graminis (DC.) E. O. Speer f. sp. tritici Em. Marchal], on performance of 50 soft red winter (SRW) wheat (Triticum aestivum L) cultivars were evaluated under natural field conditions. Widely grown cultivars released from 1919 to 2009 with varying disease resistance were grown in split-plot experiments in 2010 and 2011. Treated replications received seed treatments of triadimenol, captan and imidacloprid and foliar applications of propiconazole and prothioconazole + tebucanazole fungicides. Non-treated replications received only tebucanazole + metalaxyl + imazalil seed treatments. Final mean disease severity, agronomic, yield-related traits, yield components and spike characteristics were analyzed to determine individual and combined effects of leaf rust and powdery mildew on the cultivars. Yield losses as high as 54% were observed in the susceptible cultivar Red May. Average yield losses ranged from 1% to 21%. Yield losses primarily due to powdery mildew were as high as 14%, and losses primarily due to leaf rust were as high as 33%. Powdery mildew had the largest negative correlation with harvest index and seeds/spike. Leaf rust was most negatively correlated with plant biomass and harvest index, with a less consistent negative relationship with kernel weight.