Expression of resistance to Atherigona soccata in F1 hybrids involving shoot fly-resistant and susceptible cytoplasmic male-sterile and restorer lines of sorghum

In recent years, cytoplasmic male‐sterility (CMS) has been recognized as a potential danger to the stability of crop production and resistance to insect pests in sorghum. Therefore, the influence of CMS on the expression of resistance to sorghum shoot fly was studied at the ICRISAT, Patancheru, India using the interlard fishmeal technique. The experimental material consisted of 12 restorer, 12 CMS and the maintainer lines, and their 144 F₁ hybrids. Shoot fly‐resistant CMS lines were preferred for oviposition and had more damage because of deadhearts than the corresponding maintainer lines. The hybrids based on shoot fly‐resistant CMS × resistant restorer lines were significantly less preferred for oviposition than the hybrids based on other cross combinations and exhibited the highest frequency (69.1%) of shoot fly‐resistant hybrids. The hybrids based on glossy and trichomed parents had the highest frequency (>90%) of hybrids with glossy and trichome traits, emphasizing the need to transfer these traits into both parents for better expression in the F₁ hybrids. The expression pattern of trichome density, leaf glossiness and leaf sheath pigmentation in the F₁ hybrids and their parents suggested that the interactions between cytoplasmic and nuclear genes possibly control the expression of traits associated with resistance to sorghum shoot fly in the F₁ hybrids.     

Genetic Divergence and Molecular Characterization of Sorghum Hybrids and their Parents for Reaction to Atherigona Soccata (Rondani)

Summary Simple sequence repeat (SSR) markers linked to quantitative trait loci (QTL) associated with resistance to sorghum shoot fly, Atherigona soccata resistance were used to characterize the genetic and phenotypic diversity of 12 cytoplasmic male-sterile (CMS) and maintainers, 12 restorer lines, and 144 F₁ hybrids. The genetic diversity was quite high among the shoot fly-susceptible parents and the hybrids based on them, as indicated by high polymorphic information content (PIC) values, while limited genetic diversity was observed among shoot fly-resistant lines. The phenotypic and genotypic dissimilarity analysis indicated that the shoot fly-resistant and -susceptible parents were 73.2 and 38.5% distinct from each other, and the morphological and genetic distances of certain resistant and susceptible cross combinations was more than their resistant or susceptible parents. Genetic variability among the groups was low (10.8%), but high within groups (89.2%). The genetic and morphological distances suggested that the F₁ hybrids were closer to CMS (5 to 12% dissimilar) than the restorer (11 to 87% dissimilar), suggesting that CMS influences the expression of resistance to sorghum shoot fly. The SSR markers can be used to characterize the homologous traits in sorghum germplasm.     

Compensation in grain weight and volume in sorghum is associated with expression of resistance to sorghum midge, Stenodiplosis sorghicola

Sorghum midge, Stenodiplosis sorghicola (Coquillett) is one of the most important pests of grain sorghum worldwide. We studied the inheritance of resistance to sorghum midge and compensation in grain weight and volume in panicles of sorghum hybrids and their parents under uniform infestation (40 midges per panicle for two consecutive days). Sorghum midge damage ranged from 8.2 to 82.4% in the maintainer lines (B-lines) of the females parents (A-lines), and 9.0 to 67% in the male parents (restorer lines). Hybrids involving resistant × resistant parents were highly resistant, while those involving resistant ×susceptible and susceptible × resistant parents showed moderate susceptibility. Susceptible × susceptible hybrids were susceptible. Compensation in (percentage increase) grain weight and volume in midge-infested panicles of midge-resistant parents and their F₁ hybrids was greater than in midge-susceptible parents and hybrids. General combining ability effects for midge damage, and grain weight and volume were significant and negative for the midge-resistant females (ICSA 88019 and ICSA 88020), whereas those for the midge-susceptible females (ICSA 42 and 296A) were significant and positive. However, the reverse was true in case of compensation in grain weight and volume. Inheritance of compensation in grain weight and volume and resistance to sorghum midge is controlled by quantitative gene action with some cytoplasmic effects. Resistance is needed in both parents to realize full potential of midge-resistant hybrids. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cytoplasmic male-sterility and source of pollen influence the expression of resistance to sorghum midge, Stenodiplosis sorghicola

Sorghum midge, Stenodiplosis (Contarinia) sorghicola (Coquillett), is an important pest of grain sorghum, and host plant resistance is an important aspect of control of this pest. This research investigated how cytoplasmic male-sterility and source of pollen influence the expression of resistance to sorghum midge. Sorghum midge emergence was significantly lower in panicles of midge-resistant and midge-susceptible cytoplasmic male-sterile lines when pollinated with AF 28 - a midge-resistant restorer line, than those pollinated with Swarna - a midge susceptible restorer line, indicating the presence of xenia effects. Maintainer lines (B-lines) of midge-resistant parents had significantly lower numbers of eggs and larvae than the B-lines of midge-susceptible parents. Male-sterile lines of the both midge-resistant and midge-susceptible lines were equally susceptible, indicating that resistance to sorghum midge is influenced by factors in the cytoplasm of the B-line. These findings will have an important bearing on the production of hybrids with resistance to insects. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relative susceptibility of different male-sterile cytoplasms in sorghum to shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis>

Summary The shoot fly, Atherigona soccata is an important pest of sorghum, and host plant resistance is one of the most effective components for managing this pest. Most of the hybrids grown in India based on milo cytoplasm (A₁ cytoplasm) are highly susceptible to shoot fly. Therefore, the present studies were undertaken to evaluate different male-sterile cytoplasms (CMS) for their relative susceptibility to sorghum shoot fly. Oviposition and deadheart formation were significantly lower on the maintainer lines as compared to the corresponding male-sterile lines. Among the cytoplasms tested, A₄M cytoplasm showed antixenosis for oviposition and suffered lower deadheart formation than the other cytoplasms tested. The A₄G₁ and A₄M cytoplasms suffered lower deadhearts in tillers than the other cytoplasms. Recovery following shoot fly damage in A₄M, A₃, and A₂ cytoplasms was better than in the other cytoplasms tested. The larval and pupal periods were longer and male and female pupal weights lower in A₄M and A₄VzM CMS backgrounds compared to the other CMS systems. Fecundity and antibiosis indices on CMS lines were lower than on the B-lines. The A₄M cytoplasm was found to be relatively resistant to sorghum shoot fly, and can be exploited for developing shoot fly-resistant hybrids for sustainable crop production in future.     

Mechanisms of resistance to shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis> in sorghum

Summary Sorghum shoot fly, Atherigona soccata (Rondani) is an important pest of sorghum in Asia, Africa, and Mediterranean Europe, and host plant resistance is an important component for the management of this pest. The levels of resistance in the cultivated germplasm are low to moderate, and therefore, it is important to identify genotypes with different mechanisms of resistance to pyramid the resistance genes. We studied the antixenosis for oviposition, antibiosis, and tolerance components of resistance in a diverse array of shoot fly-resistant and -susceptible genotypes. The main plants and tillers of SFCR 151, ICSV 705, SFCR 125, and, IS 18551 experienced lower shoot fly deadhearts at 28 days after seedling emergence, produced more number of productive tillers. The insects fed on these genotypes also exhibited longer larval period (10.1–11.0 days compared to 9.3 days on Swarna), lower larval survival and adult emergence (54.7–67.8 and 46.7–52.2% compared to 73.3 and 60.6% on Swarna, respectively), and lower growth and adult emergence indices as compared to the susceptible check, Swarna. Physico-chemical traits such as leaf glossiness, trichome density, and plumule and leaf sheath pigmentation were found to be associated with resistance, and chlorophyll content, leaf surface wetness, seedling vigor, and waxy bloom with susceptibility to shoot fly and explained 88.5% of the total variation in deadhearts. Step-wise regression indicated that 90.4% of the total variation in deadhearts was due to leaf glossiness and trichome density. The direct and indirect effects, correlation coefficients, multiple and step-wise regression analysis suggested that deadhearts, plants with eggs, leaf glossiness, trichomes on the abaxial surface of the leaf, and leaf sheath pigmentation can be used as marker traits to select for resistance to shoot fly, A. soccata in sorghum.     

食葵主要经济性状的配合力及杂种优势分析

选用农家种改良过的6个食葵细胞质雄性不育系和4个优良的分枝型恢复系为亲本,按NCⅡ遗传交配设计,配成24个F₁杂种,研究了9个主要经济性状,即株高、茎粗、生育期、盘径、单盘总粒数、单盘实粒数、结实率、百粒重、单株产量的配合力及杂种优势表现。结果显示：（1）不育系中有8个性状,恢复系中有7个性状的一般配合力差异达显著或极显著水平;有4个性状的特殊配合力差异达到显著或极显著水平;（2）株高、茎粗、生育期、盘径、百粒重等5个性状主要受基因的加性效应控制;单盘总粒数、单盘实粒数、结实率、及单株产量等4个性状则受基因的加性效应和非加性效应共同影响;（3）从GCA分析看,参试的不育系以A6最为理想,A2次之;恢复系则以C3最为理想。从SCA分析看,组合A2C1单株产量效应值最高;（4）杂种优势分析表明,大部分经济性状存在杂种优势,甚至相当一部分存在超亲优势,并且这些优势都是可利用的,F₁多倾向于早熟、粗壮、高杆、大盘、多粒亲本。     

印水型杂交粳稻产量及产量构成因素的配合力分析

为确定新育成印水型杂交粳稻亲本的潜力,并为印水型杂交粳稻育种提供理论基础,本研究以4个不育系和4 个恢复系为亲本进行不完全双列杂交,研究产量及其构成因素的配合力。结果表明：产量性状一般配合力(GCA)方差均达到极显著水平,除结实率外,父本的一般配合力方差大于母本,单株产量、有效穗和结实率的特殊配合力(SCA)方差达到显著或极显著水平。139A和晚轮422 的GCA效应较高,产量性状以Ⅱ类为主,139A×晚轮422 和辽粳10A×晚轮422 的单株产量水平及组合SCA效应较高。父本GCA效应和组合SCA效应对产量性状的影响较大,母本GCA效应对产量性状的影响相对较小。本研究中,父本的遗传差异大于母本,对产量性状的影响也大于母本,139A和晚轮422 有较大的应用潜力。     

Genetic analysis of biotype I greenbug resistance in sorghum

The greenbug has been a major insect pest of sorghum since 1968. Although sources of genetic resistance have been identified to combat this pest, new and virulent biotypes have successfully overcome these resistance genes. KS 97 was developed and released by the Kansas Agricultural Experiment Station as a new germplasm source of biotype I greenbug resistance in sorghum. The objectives of this study were to evaluate combining ability effects for greenbug resistance in KS 97 and to determine the number of genes responsible for this trait. Six inbred lines, including KS 97 and greenbug resistant and susceptible checks, were intercrossed using a Design-II mating scheme to produce nine F1 hybrids. Responses of seedlings of parent lines and hybrids to biotype I greenbug were evaluated in replicated growth chamber experiments. The results of these studies indicated significant effects of general combining ability (GCA) and specific combining ability (SCA). Greenbug resistance derived from KS 97 was found to be incompletely dominant, and the GCA effect for resistance associated with KS 97 was superior to that associated with PI550610, the resistant check. Segregation studies to determine the number of genes responsible for greenbug resistance in KS 97 were conducted in BC1F1 populations. KS 97 was introgressed into three greenbug-susceptible genetic backgrounds. Segregation analysis indicated a consistent 1:3 (resistant:susceptible) segregation ratio for greenbug resistance across populations. The simplest explanation for these results is that two dominant genes requiring complementary gene action control resistance. This revised version was published online in August 2006 with corrections to the Cover Date.     

Smut reaction of pearl millet hybrids affected by fertility restoration and genetic resistance of parental lines

Summary Pearl millet (Pennisetum glaucum (L.) R. Br.) hybrids based on the A₁ cytoplasmic-nuclear male-sterile (CMS) lines are more susceptible to smut (Tolyposporium penicillariae Bref.) than open-pollinated varieties. Seventy eight pairs of hybrids, made onto male-sterile (A) lines and their counterpart maintainer (B) lines, were evaluated to examine the effects of male sterility and genetic resistance of parental lines on the smut severity of hybrids. The A-line hybrids had higher smut severity and lower selfed seedset than the counterpart B-line hybrids, indicating that it is the CMS-mediated male sterility rather than the A₁ cytoplasm per se that caused greater smut severity of A-line hybrids. However, with the use of resistant parental lines even male-sterile hybrids of A-lines, in several cases, were as resistant as some of the highly resistant male-fertile hybrids of B-lines. It would be possible to produce smut resistant hybrids (< 10% severity) on A-lines, albeit in low frequency, even if only one parent of a hybrid were resistant. However, the probability of producing such hybrids would be higher when both parents were resistant to smut. Thus, improvement in smut resistance of parental lines and fertility restoration ability of pollinators would provide the most effective genetic approach to smut disease management in hybrids.Submitted as JA No 1737 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).     

Leaf and neck blast resistance reaction in tropical rice lines under green house condition

Rice blast (Magnaporthe oryzae) is the most destructive and epidemic disease of rice. Use of host resistance is the best alternative for disease management. The leaf and neck blast resistance of 182 rice breeding lines were assessed for leaf and neck blast and classified relative to a susceptible check-Masuli and resistant check-Laxmi, from greenhouse experiment in 2005 and 2006. The test plants were inoculated with 10⁵ conidial suspension/ml of M. oryzae at 21 days old seedlings for the leaf blast, and at neck base for the neck blast. Among them, for leaf blast, 77 rice lines were resistant, 43 were moderately resistant, 39 were moderately susceptible and 23 were susceptible. While among the selected 31 rice lines evaluated for neck blast, 4 lines were resistant, 4 were moderately resistant, 16 were moderately susceptible and 7 were susceptible. Leaf and neck infection was significant and positively correlated (r = 0.30, P = 0.05). The rice lines, Barkhe 1032, Barkhe 1034, Barkhe 1035, Barkhe 1036, Barkhe 2014, Barkhe 2024, Barkhe 3019, Super 3004 were resistant to leaf blast and Barkhe 1006, Barkhe 1032, Barkhe 1035, Barkhe 3004 were resistant to neck blast. The rice lines with identification # 11, 69, 137, 168, 182 from Masuli × MT4 parentage, and Barkhe 3017 were susceptible to both leaf and neck blast. Progenies of Irradiated Pusa Basmati (IPB), Kalinga III/IR64 (KIII/IR64), and Masuli/IR64 were resistant to both leaf and neck blast. However, most progenies from Masuli/MT4 showed susceptible reaction to both leaf and neck blast. Thus, rice lines form the IPB, KIII/IR64 and Masuli/IR64 will be promising resistant sources for rice blast in breeding programme.     

A comparison of cytoplasmic and chemically-induced male sterility systems for hybrid seed production in wheat (Triticum aestivum L.)

A comparison of two male sterility systems was carried out in wheat for hybrid seed production and hybrid performance. Seventeen hybrid combinations based on Triticum timopheevi cytoplasm were compared with their genetically equivalent CHA-facilitated combinations. The same set of restorer lines was used as parents in CMS- and CHA-based hybrids to maintain genetic equivalence. In the first experiment aimed at study of female line behavior and crossed seed production, the CHA treated lines showed significantly shorter heights whereas CMS lines were similar to the control. The two systems were equally effective in sterilizing rate. The outcrossing percentage of the CMS lines was almost twice that of the CHA treated lines. Thousand-grain weight of the crossed seeds on CMS lines was greater than on the CHA treated lines and control. On average, the germination percentage of seeds on CMS lines was double that of the CHA treated lines and the percentage of effective outcrossed seeds in CMS lines was 3 times more than that from CHA treated lines. The second experiment was conducted to examine the yield performance of the hybrids derived from the two systems of male sterility. A total of 40 entries including 20 hybrids and 20 parents were evaluated in the experiment. The mean grain yield of the CMS-based hybrids was greater than that of the CHA-based hybrids,the B and R lines. All the CMS-based hybrids showed significantly higher grain yields than their better parents whereas all the CHA-based hybrids, except two,showed no significant yield increases over their better parents. Possible reasons for differences in CMS- and CHA-based hybrid performance are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation in inheritance of resistance to sorghum midge, Stenodiplosis sorghicola across locations in India and Kenya

Sorghum midge [Stenodiplosis sorghicola (Coquillett)] is an important pest of grain sorghum, and host plant resistance is one of the important components for the management of this pest. We studied the inheritance of resistance to this insect involving a diverse array of midge-resistant and midge-susceptible genotypes in India and Kenya. Testers IS 15107, TAM 2566, and DJ 6514, which were highly resistant to sorghum midge in India, showed a greater susceptibility to this insect in Kenya. The maintainer lines ICSB 88019 and ICSB 88020 were highly resistant to sorghum midge in India, but showed a susceptible reaction in Kenya; while ICSB 42 was susceptible at both the locations. General combining ability (GCA) effects for susceptibility to sorghum midge for ICSA 88019 and ICSA 88020 were significant and negative in India, but such effects were non-significant in Kenya. The GCA effects of ICSB 42 for susceptibility to sorghum midge were significant and positive at both the locations. The GCA effects were significant and positive for Swarna, and such effects for IS 15107 and TAM 2566 were negative at both the locations. GCA effect of DJ 6514 were significant and negative in India, but non-significant and positive in Kenya; while those of AF 28 were significant and positive during the 1994 season in India, but significant and negative in Kenya. Inheritance of resistance to sorghum midge is largely governed by additive type of gene action. Testers showing resistance to sorghum midge in India and/or Kenya did not combine with ICSA 88019 and ICSA 88020 to produce midge-resistant hybrids in Kenya. Therefore, it is essential to transfer location specific resistance into both parents to produce midge-resistant hybrids.     

Improvement of Sclerotinia resistance of a Polima CMS restorer line of rapeseed via phenotypic selection, marker-assisted background selection and microspore culture

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most severe diseases of rapeseed in China and other major growing regions. The objective of this study was to improve the S. sclerotiorum resistance of 'Hui5200', an elite 'Polima' CMS restorer line, by introgression and fixation of resistance alleles from the partially resistant cultivar 'NingRS-1' via phenotypic selection (PS), marker-assisted background selection (MAB) and microspore culture. A progeny designated as 'RSH' with greatly improved Sclerotinia resistance and a similar genetic background as 'Hui5200' was obtained by two backcrosses and one selfing. From a selected elite progeny line (named as 7-5) double haploid (DH) lines were developed. By three cycles of PS considering economic traits and genetic distance analysis, four resistant DH restorer lines with elite economic traits were finally selected. The obtained resistant restorer lines have been used to produce commercial F₁ hybrids. The results indicated that backcrossing plus PS and MAB is effective and suitable for improving resistance of rapeseed to S. sclerotiorum .     

Inheritance of trichomes and resistance to pod borer (Helicoverpa armigera) and their association in interspecific crosses between cultivated pigeonpea (Cajanus cajan) and its wild relative C. scarabaeoides

The legume pod borer, Helicoverpa armigera, is one of the most devastating pests of pigeonpea. High levels of resistance to pod borer have been reported in the wild relative of pigeonpea, Cajanus scarabaeoides. Trichomes (their type, orientation, density and length) and their exudates on pod wall surface play an important role in the ovipositional behavior and host selection process of insect herbivores. They have been widely exploited as an insect defense mechanism in number of crops. In the present investigation, inheritance of resistance to pod borer and different types of trichomes (A, B, C and D) on the pod wall surface in the parents (C. cajan and C. scarabaeoides) and their F₁, F₂, BC₁ (C. cajan × F₁), and F₃ generations has been studied. Trichomes of the wild parents (high density of the non-glandular trichomes C and D, and glandular trichome B and low density of glandular trichome A) were dominant over the trichome features of C. cajan. A single dominant gene as indicated by the segregation patterns individually will govern each trait in the F₂ and backcross generation. Segregation ratio of 3 (resistant): 1 (susceptible) for resistance to pod borer in the F₂ generation under field conditions was corroborated with a ratio of 1:1 in the backcross generation, and the ratio of 1 non-segregating (resistant): 2 segregating (3 resistant: 1 susceptible): 1 non-segregating (susceptible) in F₃ generation. Similar results were obtained for pod borer resistance under no-choice conditions. Resistance to pod borer and trichomes associated with it (low density of type A trichome and high density of type C) are governed individually by a dominant allele of a single gene in C. scarabaeoides. Following backcrossing, these traits can be transferred from C. scarabaeoides into the cultivated background.     

Pattern of genetic inheritance of morphological and agronomic traits of sorghum associated with resistance to sorghum shoot fly, <Emphasis Type="Italic">Atherigona soccata</Emphasis>

Sorghum shoot fly, Atherigona soccata is an important pest of sorghum during the seedling stage, which influences both fodder and grain yield. To understand the nature of inheritance of shoot fly resistance in sorghum, we performed generation mean analysis using two crosses IS 18551 × Swarna and M 35-1 × ICSV 700 during the 2013–2014 cropping seasons. The F₁, F₂, BC₁ and BC₂ progenies, along with the parental lines were evaluated for agronomic and morphological traits associated with resistance/susceptibility to sorghum shoot fly, A. soccata. The cross IS 18551 × Swarna exhibited significant differences between the parents for shoot fly deadhearts (%) in the postrainy season. The progenies of this cross exhibited lower shoot fly damage, suggesting that at least one of the parents should have genes for resistance to develop shoot fly-resistant hybrids. Leaf glossiness, leafsheath pigmentation and plant vigor score during the seedling stage exhibited non-allelic gene interactions with dominant gene action, whereas 100 seed weight showed both additive and dominant gene interactions. Presence of awns showed recessive nature of the awned gene. Generation mean analysis suggested that both additive and dominance gene effects were important for most of the traits evaluated in this study, but dominance had a more pronounced effect.     

Genetical analysis of resistance to Mycosphaerella pinodes in pea seedlings

Summary In studies of the inheritance of resistance, pea seedlings of seven lines in which stems and leaves were both resistant to Mycosphaerella pinodes were crossed with a line in which they were both susceptible. With seven of the crosses resistance was dominant to susceptibility. When F₂ progenies of five crosses were inoculated on either stems or leaves independently, phenotypes segregated in a ratio of 3 resistant: 1 susceptible indicating that a single dominant gene controlled resistance. F₂ progenies of one other cross gave ratios with a better fit to 9 resistant: 7 susceptible indicating that two co-dominant genes controlled resistance. The F₂ progeny of another cross segregated in complex ratios indicating multigene resistance.When resistant lines JI 97 and JI 1089 were crossed with a susceptible line and leaves and stems of each F₂ plant were inoculated, resistance phenotypes segregated independently demonstrating that leaf and stem resistance were controlled by different genes. In two experiments where the F₂ progeny of the cross JI 97×JI 1089 were tested for stem and leaf resistance separately, both characters segregated in a ratio of 15 resistant:1 susceptible indicating that these two resistant lines contain two non-allelic genes for stem resistance (designated Rmp1 and Rmp2) and two for leaf resistance (designated Rmp3 and Rmp4). Evidence that the gene for leaf resistance in JI 1089 is located in linkage group 4 of Pisum sativum is presented.     

培育水稻恢复系抗稻褐飞虱基因导入系和聚合系

稻褐飞虱是水稻的主要虫害之一,培育优良的抗性基因聚合系对于防治稻褐飞虱具有重要的意义.本研究通过回交、分子标记辅助选择和接虫鉴定三者相结合的办法,将抗稻褐飞虱基因Bph3和Bph24(t)分别导入主栽杂交水稻恢复系广恢998、9311、R15、明恢63、R29中,最终获得遗传稳定的Bph3导入系32份和Bph24(t)...     

Brassica coenospecies: a rich reservoir for genetic resistance to leaf spot caused by Alternaria brassicae

Development of leaf spot resistant mustard cultivars is a relevant objective in view of heavy crop losses caused by this pathogen. Thirty-eight species belonging to 9 genera, including cultivated and wild allies, of the genus Brassica were evaluated under epiphytotic conditions for two years. Inoculations were done on whole plants (in vivo) and on detached leaves (in vitro). Data on incubation period, number of lesions per leaf, lesion size and leaf area covered by lesions were recorded. Species which never produced disease symptoms throughout the growing period in pots and until 72 hours after inoculation in detached leaf assays during both years were treated as resistant, while those that produced symptoms were classified as moderately resistant, susceptible or highly susceptible depending upon incubation period, size of lesions and leaf area covered by disease symptoms. Eight species (Brassica desnottesii, Camelina sativa, Coincya pseuderucastrum, Diplotaxis berthautii, D. catholica, D. cretacea, D. erucoides, and Erucastrum gallicum) were found completely resistant, whereas others were classified as moderately resistant (12), susceptible (11) or highly susceptible (9). Since resistance is unavailable within the cultivated species, these 8 resistant wild species could be used as donor parents for introgressing resistance to leaf spot disease in Indian mustard. This revised version was published online in August 2006 with corrections to the Cover Date.     

Are ordinal rating scales better than percent ratings? a statistical and “psychological” view

Cytoplasmic male sterility (CMS) is considered an efficient genetic tool in pearl millet hybrid breeding. Of the several CMS sources available in pearl millet, A₁ is the only CMS widely exploited to produce commercial hybrids in India. To explore the possibility of using alternate CMS sources, we studied the cytoplasmic effects of different CMS sources on agronomic characters in pearl millet. Five CMS (A) lines representing A₁, A₂, A₃, A₄ and A₅ cytoplasms, their respective maintainer (B) lines and eight restorer (R) lines were used to generate 40 A × R and B × R experimental crosses. The experimental material was evaluated at two different locations in India. Analysis of combining ability and heterosis revealed that A₄ and A₅ cytoplasms had desirable effects for earliness. The A₅ CMS was found to be particularly promising, as compared to other CMS sources for improving grain yield. The study also indicated that the cytoplasmic effects on general combining ability (GCA) for various agronomic characters were largely non-significant. However, cytoplasmic effects on specific combining ability and heterosis were found to be modulated by cytoplasmic-nuclear interactions and influenced by the environmental conditions. The study also demonstrated the advantage of utilizing diverse male-sterile and restorer combinations in maximizing the productivity as well as for genetic and cytoplasmic diversification of hybrids in pearl millet.