苗期遮荫对棉花产量与品质形成的影响

为揭示棉麦两熟共生期遮荫对棉花产量与品质形成的影响。在棉花苗期利用模拟棉麦两熟共生期遮荫的方法进行了研究。结果表明,遮荫对棉铃形成的影响因果枝,果节部位而异,遮荫有利于棉株下（1-3果枝）,中（4-6果枝）,上（7-9果枝）部果枝内围（1-2果节）铃的形成,对外围（≥3果节）尤其顶部果枝（≥10果枝）外围铃形成不利,从而决定铃重也随果枝,果节部位相应地变化,但遮荫对单株平均铃重的影响畔 小,变遮荫棉花籽棉产量而论,下,中部果枝的内围铃籽棉产量高于常规棉,在上,顶部果枝则相反,各部位果枝外围铃的籽棉产量均低于常规棉,遮荫棉花内,外围铃分布为1：0.36(常规棉为1：0.58),产量分布为1：0.42(常规棉为1：0.72)。苗期遮荫对棉纤维,棉籽品质性状的影响也主要在顶部果枝和上部果枝外围铃,综合分析遮荫棉花产量与品质的形成,棉花苗期耐遮荫性品种间存在差异。在本研究中以中9418耐遮荫性最强,中棉所19和春矮早次之。     

Effect of Mechanical Stress on Cotton Growth and Development

Agricultural crops experience diverse mechanical stimuli, which may affect their growth and development. This study was conducted to investigate the effects of mechanical stresses caused by hanging labels from the flower petioles (HLFP) on plant shape and cotton yields in four cotton varieties: CCRI 41, DP 99B, CCRC 21, and BAI 1. HLFP significantly reduced plant height by between 7.8% and 36.5% in all four lines and also significantly reduced the number of fruiting positions per plant in the CCRI 41, DP 99B and CCRC 21 lines. However, the number of fruiting positions in BAI 1 was unaffected. HLFP also significantly reduced the boll weight for all four cultivars and the seed cotton yields for CCRI 41, DP 99B and BAI 1. Conversely, it significantly increased the seed cotton yield for CCRC 21 by 11.2%. HLFP treatment did not significantly affect the boll count in the fruiting branches of the 1^st and 2^nd layers in any variety, but did significantly reduce those on the 3^rd and 4^th fruiting branch layers for CCRI 41 and DP 99B. Similar trends were observed for the number of bolls per FP. In general, HLFP reduced plant height and boll weight. However, the lines responded differently to HLFP treatment in terms of their total numbers of fruiting positions, boll numbers, seed cotton yields, etc. Our results also suggested that HFLP responses might be delayed for some agronomy traits of some cotton genotypes, and that hanging labels from early-opening flowers might influence the properties related with those that opened later on.     

棉花对棉铃虫为害超补偿作用的生理机制

为研究棉花对棉铃虫为害超补偿作用的生理机制,作者在山东省滨州市棉田进行了模拟第二代棉铃虫为害的试验。结果表明：每株棉花摘除8个早蕾后,最终成铃数增加13.4%,其中下部第6及其上果枝的成铃数增加较多。处理组棉叶中可溶性糖和淀粉含量上升,氨基酸含量下降,光合作用强度加大(3.6%～6.7%),叶面积系数增加8.5%～28.1%,单株生产力增大,从而揭示了超补偿作用的重要机制。     

留营养枝对棉株同化物生产,运转,分配及产量的影响

运用＾１４Ｃ示踪技术研究了留营养支棉株＾１４Ｃ同化物生产运转分配规律。结果表明：留营养枝与否对全株＾１４Ｃ总同化量基本没有影响,但留营养２枝棉株果枝叶的相对光合强度（以放射性比强度表示）降低;主茎叶、果枝叶的＾１４Ｃ同化量显著降低;营养２叶具有较高的光合作用强度和向外输送＾１４Ｃ同化物的转运速率,在＾１４Ｃ同化物生产运转分配中占有很重要的地位。留营养枝棉株＾１４Ｃ同化物的转运速率,在＾１４Ｃ同化     

不同整枝方式对棉花源库关系的调节效应

以去叶枝留早果枝的正常整枝方式为对照,于2005—2006年研究了整枝对大田棉花源库关系的调节效应.结果表明：去叶枝去早果枝（Ⅰ）、留叶枝去早果枝（Ⅱ）和留叶枝留早果枝（Ⅲ）3种整枝方式都显著促进了棉花叶面积扩展,最大叶面积系数分别比对照平均提高了10.3%、28.3%和9.5%,导致叶面积载荷量减少,源库比降低.Ⅰ和Ⅱ处理显著提高了叶片叶绿素含量,降低了始絮期的黄叶率和功能叶的C/N,表现出显著地延缓衰老的作用,但Ⅱ处理易导致贪青晚熟;而Ⅲ处理对衰老的延缓作用不大.Ⅰ处理的籽棉产量与对照相当,Ⅱ处理比对照降低了6.4%~15.6%,Ⅲ处理比对照增产6.3%.表明去早果枝和留叶枝皆是调节棉花源库关系、碳氮代谢和延缓棉花早衰的有效手段.     

Removal of early fruit branches triggered regulations in senescence,boll attributes and yield of Bt cotton genotypes

Premature senescence, unopened and rotted bolls are the primary constrictions hampering the accomplishment of yield potential in Bt cotton. An experiment was conducted with the objectives to delay senescence, enhance boll opening and reduce the boll rotting. The experiment was conducted at two randomly selected sites of University of Agriculture Faisalabad, Pakistan, during 2015 and repeated in 2016. Each experiment was laid out in randomised complete block design with two by two factorial arrangement structure and replicated five times. Treatments were comprised of R₀ = no fruit removal; R₁ = removal of early fruit branches (REFB) and two genotypes, viz. V₁ = FH‐142 and V₂ = MNH‐886. Genotypes were selected on the basis of abiotic stress tolerance (FH‐142) and susceptibility (MNH‐886). Nodes above cracked bolls, monopodial branches, opened bolls per plant and seed cotton yield were enhanced by 23, 12, 13 and 17%, respectively, under the influence of REFB over no fruit branch removal, while the REFB‐mediated decrease in boll rotting was 27%. Moreover, the response of MNH‐886 was more remarkable than FH‐142 for all studied variables. Conclusively, REFB increased the number of nodes above a cracked boll, monopodial branches, opened bolls per plant and seed cotton yield while decreased rotted bolls per plant in both genotypes.     

Reducing boll weevil populations by clipping terminal buds and removing abscised fruiting bodies

Cotton pests damaging fruiting bodies (squares and young bolls) are difficult to control and their damage results in direct yield loss. Small growers, with low technological inputs, represent a large portion of cotton growers worldwide comprising more than 76 countries; they rely mainly on cultural practices to counteract pest attack in their crops. Boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), oviposition involves puncturing cotton squares and young bolls, causing abscission. We examined the impact on boll weevil population of collecting abscised cotton fruiting bodies and clipping plant terminals at 50% boll maturation in the field during two cotton‐growing seasons and under field cage conditions. Greatest numbers of damaged squares occurred ca. 117 days after planting and clipped plants resulted in reduction of abscised structures and adult boll weevils compared with non‐clipped plants, irrespective of cotton variety. Damaged young bolls were found ca. 128 days after planting in 2009 and 2011, but clipping had no effect. Numbers of boll weevils found in plants of the varieties BRS 201 and BRS Rubi (both in 2009) and BRS Rubi (in 2011) were, respectively, 13‐, 17‐, and 20‐fold greater when clipping plus collecting abscised fruiting bodies were not practiced. Furthermore, the average percentage of the boll weevil parasitoid Bracon vulgaris Ashmead (Hymenoptera: Braconidae) emerging from abscised and collected structures was similar between clipped and non‐clipped plant terminals in both seasons. Clipping plant terminals did not result in yield reduction and reduced adult boll weevil production. Collecting abscised reproductive structures, clipping plant terminals, and using both practices together reduced boll weevil populations by as much as 63, 57, and 79%, respectively, in cage trials. Thus, these practices cause significant impact on boll weevil populations and are feasible of adoption, especially for smallholder cotton growers.     

Abscisic Acid and cutout in cotton

A decline in growth, flowering, and boll (fruit) retention is referred to as cutout in cotton (Gossypium hirsutum L.). Fruit load affects cutout, possibly through hormonal effects. Experiments were conducted to test the hypothesis that fruits are a source of abscisic acid (ABA) that moves into fruiting branches and growing points where it inhibits growth, flowering, and boll retention. Removal of the flower or young boll at the first node of fruiting branches did not decrease the ABA content of fruiting branches or the abscission zone at the second node. Effects on ABA content of the boll at the second node varied. In one field test, ABA content of bolls at the second node decreased with successive harvests as bolls were removed from first node positions of several fruiting branches. Thus, the effect was cumulative and was not limited to individual branches. Removal of the flower or boll at the first node increased boll retention at the second node. Removal of all flowers during the first 3 weeks of flowering delayed the decreases in growth, flowering, and boll retention that occurred as fruit load increased. But, the ABA content of fruiting branches and mainstem apices was not decreased by early defruiting and did not increase with increasing fruit load. The results do not support the hypothesis that fruits are a source of ABA that moves into fruiting branches and growing points where it then inhibits growth, flowering, and boll retention.     

The degree of susceptibility of nectary-inoculated cotton flowers and bolls to subsequent seed infection by Aspergillus flavus is determined at or before anthesis

In greenhouse and field studies, cotton (Gossypium hirsutum L.) flowers were inoculated with Aspergillus flavus at the involucral nectaries. Bolls developing from early-season flowers had significantly higher percentages of A. flavus-infected seed than did bolls from flowers formed later in the season. Seeds from bolls inoculated 2 weeks after anthesis had the same infection levels as those from flowers inoculated at anthesis. These results indicate that early-season flowers are predisposed to A. flavus infection and that the degree of susceptibility at anthesis is retained through early boll development.     

Injury to preflowering and flowering cotton by brown stink bug and southern green stink bug

The impact of brown stink bug, Euschistus servus (Say), and southern green stink bug, Nezara viridula (L.), injury was evaluated on preflowering and flowering cotton, Gossypium hirsutum L., plants in no-choice tests. Vegetative stage cotton seedlings and reproductive structures, including flower buds (square) and bolls, were infested with adults and/or nymphs of both species. There were no significant differences in height, height to node ratio, square retention, and flower initiation for cotton seedlings or plants with a match-head square between southern green stink bug adult- or brown stink bug adult-infested and noninfested treatments. Abscission for individual large squares (precandle) and multiple squares (medium and small square on the same sympodial branch) was not significantly different among infested and noninfested treatments for the following species and developmental stages: brown stink bug adults, southern green stink bug adults, and third and fourth to fifth instar southern green stink bug nymphs. In boll infestation studies, the relationship between boll maturity, expressed as heat units beyond anthesis, and boll growth, abscission, hard locked carpels, seedcotton yield, and seed germination was measured. Brown stink bug induced abscission in bolls that had accumulated > 0-350 heat units beyond anthesis. Boll growth and seedcotton yield was significantly lower for bolls infested with brown stink bug through 266.5 and 550 heat units beyond anthesis, respectively. The proportion of hard locked carpels per boll was significantly greater for the infested treatment in a cohort of bolls that accumulated from 51 to 400 heat units beyond anthesis. Seed germination in bolls infested with brown stink bug was significantly lower in bolls aged 101-600 heat units beyond anthesis.     

Recovery from terminal and fruit damage by dry season cotton crops in tropical Australia

We conducted a 2-yr field study on growth and yield compensation in cotton (Gossypium hirsutum L.) after artificial pest damage in Kununurra in NW Australia. The aim was to assess the responses of cotton grown in tropical Australia to simulated Helicoverpa damage early in the season (tip damage) and during fruiting (square removal). In this region, cotton is grown in an inverse temperature regimen to cotton grown in temperate regions, and it is possible that tropical cotton crops exhibit different responses to pest damage (Yeates 2001). To examine this, we imposed manual damage treatments by excising plant tips before squaring (flower bud production) and removing all large squares at 800 degree-days DD, (at base 12 degrees C; early square loss) or 1,200 DD (mid-square loss). We found high levels of tolerance in tropical cotton to simulated pest damage (particularly early square loss) equaling or possibly surpassing the compensatory response of cotton grown in temperate Australia. While yield did not differ between damage and control treatments, the trend suggests an increase in yield resulting from tip damage and early fruit loss. Compared with temperate crops, the delay in maturity caused by damage was minimal, owing to high rates of boll opening (up to 11% d(-1)). Early season tip damage resulted in a significant increase in lateral branch growth that later contributed to a higher fruiting potential. The altered canopy of tip-damaged plants also increased light interception, particularly in the upper canopy. Both of the above factors could confer a greater tolerance to subsequent fruit damage in tipped plants.     

Nucleolar Activity in Differentiating Cotton Fibres is Related to the Position of the Boll on the Plant

Significant differences in nucleolar size at early stages ofcotton fibre development have been observed between bolls ofdifferent fruiting branches. Cutting off the apex or removalof the leaf subtending the cotton boll 6 d before floweringor emasculation followed by an addition of GA₃ resulted in asignificant decrease of the nucleolar size. Excising half ofthe roots had no influence on the nucleolar activity. The differencesin nucleolar size between bolls of the first and fifth fruitingbranches remained significant except in the case where the leafsubtending the boll was removed. Key words: Cotton fibres, nucleolus, gibberellin     

Photosynthesis and plant growth response of transgenic Bt cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) hybrids under field condition

Field experiments were conducted under rain-fed conditions to study the growth and photosynthetic efficiency of transgenic Bt cotton hybrids during 2002–03 and 2003–04 seasons. Three Bt cotton hybrids (Bollgard 1) and their non-Bt (NBt) counterparts viz. MECH 12, MECH 162, and MECH 184 were grown along with a local hybrid NHH44. Growth parameters such as plant height, main-stem nodes, biomass accumulation, and physiological processes like stomatal conductance (g _s), and rates of transpiration (E) and photosynthesis (P _N) did not differ significantly between Bt and NBt hybrids up to 80 DAS (d after sowing). Squaring commenced at 50 DAS both in Bt and NBt. The loss of young fruiting forms by the entomological factors was three times less in Bt than NBt. As a consequence, Bt had more early formed bolls on the lower canopy which contributed to higher biomass and seed cotton yield. On the other hand, bolls distributed intermittently in NBt. Heavy boll load altered the growth and physiological processes, and as a result Bt had higher g _s, E, and P _N than NBt. Since developing bolls (sink) divert the saccharides and nutrients from other organs, Bt plants with heavy boll load senesced early and stopped the production of new squares and bolls. Thus, the boll load influenced the change in growth and physiological processes of Bt from NBt.     

Relationships of abscised cotton fruit to boll weevil (Coleoptera: Curculionidae) feeding, oviposition, and development

Abscised cotton, Gossypium hirsutum L., fruit in field plots planted at different times were examined to assess adult boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), use of squares and bolls during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Although boll abscission is not necessarily related to infestation, generally more bolls abscised than squares and abundances of fallen bolls were not related to the planting date treatments. During 2003, fallen squares were most abundant in the late-planted treatment. Although large squares (5.5-8-mm-diameter) on the plant are preferred for boll weevil oviposition, diameter of abscised squares is not a reliable measurement because of shrinkage resulting from desiccation and larval feeding. Fallen feeding-punctured squares and bolls were most abundant in late plantings but differences between fallen feeding-punctured squares versus fallen feeding-punctured bolls were found in only one treatment in 2003. During the same year, fallen oviposition-punctured squares were more numerous in the late-planted treatment than in the earlier treatments. Treatment effects were not found on numbers of oviposition-punctured bolls, but fallen oviposition-punctured squares were more common than bolls in the late-planted treatment compared with earlier treatments each year. Dead weevil eggs, larvae, and pupae inside fallen fruit were few and planting date treatment effects were not detected. Living third instars and pupae were more abundant in fallen squares of the late-planted treatment than in the earlier treatments and bolls of all three treatments. This study shows that fallen squares in late-planted cotton contribute more to adult boll weevil populations than bolls, or squares of earlier plantings.     

The Degree of Susceptibility of Nectary-Inoculated Cotton Flowers and Bolls to Subsequent Seed Infection by Aspergillus flavus Is Determined at or before Anthesis

In greenhouse and field studies, cotton (Gossypium hirsutum L.) flowers were inoculated with Aspergillus flavus at the involucral nectaries. Bolls developing from early-season flowers had significantly higher percentages of A. flavus-infected seed than did bolls from flowers formed later in the season. Seeds from bolls inoculated 2 weeks after anthesis had the same infection levels as those from flowers inoculated at anthesis. These results indicate that early-season flowers are predisposed to A. flavus infection and that the degree of susceptibility at anthesis is retained through early boll development.     

Longevity and egg development of adult female boll weevils fed exclusively on different parts and stages of cotton fruiting bodies

The capacities of the rind (i.e., the developing calyx and petals of squares; and the outer casing, or husk, of bolls) and the internal reproductive portion of cotton, Gossypium hirsutum L. (Malvaceae), squares of three sizes, and bolls of three ages to influence adult female boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), longevity and egg production were evaluated in laboratory bioassays. While feeding on the reproductive portion of squares was expected to support adult boll weevils for considerable periods of time (e.g., medium square reproductive portion: ≈185 days), feeding on rinds also resulted in substantial longevity (e.g., medium square rind: ≈120 days). As anticipated, feeding on the reproductive portion of squares resulted in formation of chorionated eggs in mated females, but a diet comprised exclusively of rinds, particularly from large squares, was associated with gravidity and high fecundity relative to rinds of young and mature bolls. The reproductive portion and rind of post‐bloom and young bolls as sources of food resulted in limited gravidity while mature bolls were not associated with any egg formation. These findings further our understanding of how boll weevils feed on different parts of the cotton plant and how those parts as food sources are related to the biology and ecology of the boll weevil.     

Nutrient uptake in cotton in relation to plant architecture

Summary The studies on uptake of nitrogen, phosphorus and potassium by two morphologically contrasting varieties of cotton MCU-1 and PRS-72 (bothGossypium hirsutum L.) at weekly intervals, showed that till the bursting of early formed bolls, the former type accumulated these nutrients in larger quantities in leaves and stem than in the fruiting parts unlike the latter type where differences in nutrient contents of these organs were very narrow till the active bolling phase. From flowering onwards, the fruiting parts of PRS-72 contained more phosphorus. Because of its bushy habit more dry matter accumulated and more nutrients remained unutilised in leaves and stem of MCU-1 at harvest compared with the short-branch variety PRS-72. Though both the varieties gave the same yield of seed cotton per unit area, PRS-72 removed considerably less quantities of nitrogen, phosphorus and pottassium. The short fruiting branch character in cotton therefore appears to contribute substantially towards balanced and economic utilization of nutrients.     

花铃期干旱和渍水对棉铃碳水化合物含量的影响及其与棉铃生物量累积的关系

在池栽条件下,以美棉33B为材料,研究花铃期干旱、渍水7 d和渍水14 d处理对棉铃碳水化合物含量的影响及其与生物量累积的关系.结果表明: 干旱处理对下部果枝棉铃铃壳碳水化合物含量的影响较小,降低了中部铃壳碳水化合物含量;干旱处理上部铃壳和渍水处理铃壳可溶性糖、淀粉含量增加,蔗糖含量先降后增,且随渍水持续期延长变幅增大,蔗糖外运受阻加重.与铃壳相比,花铃期干旱和渍水处理对棉籽碳水化合物含量的影响较小.干旱和渍水7 d处理中部果枝棉铃生物量快速增长起始期提前但历时短,下部和上部棉铃生物量累积最大增长速率降低;渍水14 d处理不同果枝部位棉铃生物量累积最大增长速率均降低.相关分析表明,棉铃生物量及其最大增长速率与铃壳可溶性糖和蔗糖含量关系密切.因此,花铃期干旱和渍水影响棉铃蔗糖外运,改变棉铃生物量累积特性,是棉铃生物量降低的原因.
     

Exclusion cage studies on the impact of predation on Helicoverpa armigera in cotton

The impact of predation on Helicoverpa armigera was studied in four field cage exclusion trials on cotton in Kenya. H. armigera egg cohorts were introduced inside predator‐free and open control cages, and the impact of local predator populations on the cohort was examined. Fourteen days after inoculation, exclusion cages had four times more larvae than controls, indicating a strong impact of predation. Ants and Anthocoridae were the predominant predator groups. Exclusion cages had more damaged fruiting plant parts (squares, flowers and bolls) than the control. In the absence of predators, natural mortality of H. armigera was greater as cotton matured, and is likely to be linked to the host plant condition.     

Influence of cotton fruit stages as food sources on boll weevil (Coleoptera: Curculionidae) fecundity and oviposition

Boll weevil, Anthonomus grandis grandis Boheman (Coloeoptera: Curculionidae), populations in the Lower Rio Grande Valley of Texas increase strongly during the squaring stage, and preemptive insecticide sprays at the pinhead square stage were designed to capitalize on that association. Laboratory assays showed that cotton plant volatiles, or leaves as a food source, do not elicit egg production in wild weevils. Boll weevils fed on large (5.5-8-mm diameter) squares for 7 d resulted in > or = 3.8-fold more gravid females that developed 4.8-fold more chorionated eggs per female than weevils fed on match-head-sized squares, or postbloom, young (5-10-d-old), or old (3-5-wk-old) bolls. When presented with a choice, nongravid females preferred to feed on young and old bolls 4.7- and 8.4-fold more, respectively, than on large squares. In the field, large squares had 7.8- and 25-fold more feeding punctures than match-head-sized squares and bolls, respectively. Oviposition increased > or = 2.7-fold when females fed on large squares compared with match-head-sized squares and bolls. Greater feeding on large squares during squaring and the associated greater fecundity explain rapid weevil population buildups shortly after large squares become well established.