Cajanus platycarpus (Benth.) Maesen as the donor of new pigeonpea cytoplasmic male sterile (CMS) system

Cajanus platycarpus, a distantly related wild species, was successfully crossed with cultivated pigeonpea using embryo rescue and tissue culture techniques. Advance generation lines showed a range of desirable characters including cytoplasmic male sterility. A range of pigeonpea cultivars restored fertility and was maintained by a few lines including cultivar ICPL 85010. Clasmogamous flowers were observed in the male sterile lines. In such flowers anthers did not form di-adlephous bundle. Cytological analysis revealed that meiosis proceeded normally till the tetrad stage in those anthers with pollen grains. After which many of the pollen grains turned sterile. In the anthers with pollen grains, dehiscence was not observed, thus creating functional sterility. In many other anthers, pollen mother cells (PMCs) were not formed at all, giving rise to sepalous anthers. In conclusion two mechanisms of male sterility existed, one was premeiotic, where PMCs did not form and in the second, although PMCs gave rise to pollen grains, they were either partially or totally sterile accompanied by non-dehiscence of anther wall.     

Inheritance of seed protein in two interspecific pigeonpea (Cajanus cajan) crosses

Pigeonpea is one of the primary sources of protein for most rural communities of south Asia and Africa. The enhancement of protein from the present level of 20–22% will help masses in their nutritional well-beings. Breeders have identified high-protein (28–30%) germplasm amongst the wild relatives of pigeonpea; and these can serve as donors in breeding high-yielding high-protein cultivars. To achieve this, information on the inheritance of seed protein will be useful in organizing interspecific matings, generation advancement, and selection schemes. In the present study, two interspecific crosses, involving two pigeonpea cultivars ('Pant A2' and 'ICP 6997') and a wild species (Cajanus albicans (W. & A.)), were made to study the inheritance of seed protein in F₁, F₂, and BC₁F₁ generations. The high-protein trait was found to be controlled by two independent dominant genes with complementary effects. These genes are tagged with symbols “HPt₁” and “HPt₂”. The authors believe that now opportunities exist for enhancing the protein levels in pigeonpea through breeding approaches.     

Inheritance of compact dwarf plant type in pigeonpea (Cajanus cajan)

A compact dwarf plant type TDT2004-1 isolated from the progeny of a cross involving Cajanus cajan (cv. 'C-11') and C. cajanifolia was investigated for its inheritance. Pigeonpea genotype TDT2004-1 is semi-determinate in growth habit; short (approximately 37 cm) with reduced internodal length (1.2 cm), a compact canopy and a high harvest index (40%), while genotype TT44-4 is indeterminate in growth habit; tall (132 cm) with normal internodal length (2.3 cm), an open canopy and a low harvest index (28.9%). The inheritance study involving cross TT44-4 × TDT2004-1 showed that the compact dwarf plant type was governed by a single recessive gene. TDT2004-1 could be utilized for improving the harvest index and also for restructuring the plant canopy in pigeonpea.     

RFLP analysis of cytoplasmic male-sterile lines of pigeonpea [Cajanus cajan (L.) Millsp.] developed by interspecific crosses

Total DNA from three putative cytoplasmic male sterile (CMS) progenies derived from crosses between the wild species Cajanus sericeus and the cultivated species Cajanus cajan, five C. cajan, one accession of C. sericeus and two genetic male sterile lines of pigeonpea were compared for their RFLP patterns using maize mitochondrial DNA (mtDNA) specific probes. Three putative cytoplasmic male sterile (CMS) progenies from the multiple cross genome transfer of pigeonpea lines (CMS 7–1, CMS 12–3, and CMS 33–1) showed hybridization patterns identical to that of C. sericeus when DNA was digested with EcoRI and HindIII and probed with maize mtDNA clones. The results suggested that these putative CMS progenies have the mitochondria of the female wild species parent. The hybridization patterns of the three male parental lines used in the development of the CMS progenies were similar in all the restriction enzyme-probe combinations except HindIII-atp6. The genetic male sterile lines, MS Prabhat and QMS 1 differed from each other in their hybridization pattern. The genomic DNA hybridization pattern of HindIII digested DNA from ICPL 87 differed from the other pigeonpea lines when probed with the maize mtDNA clones. The cluster analysis of the hybridization data suggested the occurrence of variation in the mitochondrial genome even among the cultivated species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetics of fertility restoration in A2-based cytoplasmic genetic male sterility system in pigeonpea (Cajanus cajan)

The three short duration cytoplasmic genetic male sterility (CGMS) hybrids developed using A₂ (Cajanus scarabeoides) cytoplasm-based male sterile lines (CORG 990047A, CORG 990052A and CORG 7A) and the restorer inbred AK 261322 and their segregating populations (F₂ and BC₁F₁) were subjected to the study of inheritance of fertility restoration in pigeonpea. The fertility restoration was studied based on three different criteria, namely, anther colour, pollen grain fertility and pollen grain morphology and staining. The F₂ and BC₁F₁ populations of the three crosses, namely, CORG 990047A × AK 261322, CORG 990052A × AK 261322 and CORG 7A × AK 261322, segregated in the ratio of 3:1 and 1:1, for anther colour (yellow:pale yellow), pollen grain fertility (fertile:sterile) and for pollen grain morphology and staining. The above study confirmed that the trait fertility restoration was controlled by single dominant gene. This finding can be utilized for the identification of potential restorers, which can be further used in the development of CGMS-based hybrids in pigeonpea.     

Inheritance and molecular mapping of restorer‐of‐fertility (Rf) gene in A2 hybrid system in pigeonpea (Cajanus cajan)

Inheritance of fertility restorer gene in pigeonpea was studied using F₂ and BC₁F₁ populations derived from cross AL103A × IC245273. It was found to be controlled by single dominant gene. Out of 228 SSR primer pairs, 33 primer pairs showed parental polymorphism, while four primers were found polymorphic in bulk segregant analysis (BSA). These four primers viz., CcM 1615, CcM 0710, CcM 0765 and CcM 1522 were used for genotyping of F₂ population and were found to be placed at 3.1, 5.1, 28.1 and 45.8 cM, respectively. Two of them, CcM 1615 and CcM 0710, evinced clear and unambiguous bands for fertility restoration in F₂ population. The Rf gene was mapped on linkage group 6 between the SSR markers CcM 1615 and CcM 0710 with the distances of 3.1 and 5.1 cM, respectively. The accuracy of the CcM 1615 was validated in 18 restorers and six maintainer lines. The marker CcM 1615 amplified in majority of male restorer lines with a selection accuracy of 91.66%.     

Intra species variation in Atylosia scarabaeoides (L.) Benth., a wild relative of pigeonpea (Cajanus cajan (L.) Millsp.)

Summary Atylosia scarabaeoides (L.) Benth., a wild relative of pigeonpea, possesses several useful genes which can be utilized for pigeonpea improvement. In the present study, 33 accessions of A. scarabaeoides were evaluated at ICRISAT Center during the 1987 rainy season for variation in some useful traits to identify parents for inter-generic hybridization. A large variation was observed for leaf components, seed size, pod length, seeds/pod, days to flowering, seed protein, sulphur amino acids, resistance to cyst nematode, phytophthora blight, sterility mosaic, fusarium wilt, pod borer, pod fly, and pod wasp. Only four accessions were found to have more than 28% protein content. Methionine and cystine contents were marginally higher than in pigeonpea but the variation was not large enough to utilize them in the breeding program. In A. scarabaeoides. accessions resistant to fusarium wilt, phytophthora blight, sterility mosaic, and cyst nematode were detected. Compared to pigeonpea, the A. scarabaeoides accessions were less susceptible to lepidopteran borer and were immune to pod fly damage. Accessions ICPW 89 and ICPW 111 in short- (100–120 days), and ICPW 94 and ICPW 118 in medium-duration (140–180 days) were identified as potential parents for use in inter-generic hybridization.ICRISAT Journal Article No. 967     

Inheritance of resistance to two isolates of sterility mosaic pathogen in pigeonpea (Cajanus cajan (L.) Millsp.)

The resistant reaction to tomato spotted wilt virus (TSWV) was found to be determined by a single dominant gene in three Capsicum chinense Jacq. accessions (‘PI 152225’, ‘PI 159236’, ‘7204’). Allelism studies indicated that all C. chinense lines bear the same allele located at the Tsw locus. All the inoculated plants in the allelism tests displayed a resistant hypersensitive phenotype characterized by necrotic local lesions followed by abscission of the inoculated organ. However, a small proportion of them showed late systemic infection. Nine TSWV isolates obtained from these individual plants with systemic symptoms were backinoculated to the three resistant parents. All isolates were able to infect systemically all the resistant accessions without inducing local necrotic lesions. Serological analysis confirmed that these nine viral isolates belong to the TSWV species (serogroup I). Consequently, the susceptible plants in the allelism tests could not be interpreted as possessing a recombinant genotype because of the virulence change in the viral strain. Hobbs et al. (1994) already reported the existence of TSWV pathotypes overcoming the resistance of C. chinense resistant accessions. Practical consequences for pepper breeding associated with the emergence of these resistance-breaking isolates are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Role of Arbuscular Mycorrhizae in the Alleviation of Ionic, Osmotic and Oxidative Stresses Induced by Salinity in Cajanus cajan (L.) Millsp. (pigeonpea)

Salinity stress causes ion toxicity and osmotic imbalances, leading to oxidative stress in plants. Arbuscular mycorrhizae (AM) are considered bio‐ameliorators of saline soils and could develop salinity tolerance in crop plants. Pigeonpea exhibits strong mycorrhizal development and has a high mycorrhizal dependency. The role of AM in enhancing salt tolerance of pigeonpea in terms of shoot and root dry weights, phosphorus and nitrogen contents, K⁺ : Na⁺, Ca²⁺ : Na⁺ ratios, lipid peroxidation, compatible solutes (proline and glycine betaine) and antioxidant enzyme activities was examined. Plants were grown and maintained at three levels of salt (4, 6 and 8 dSm^?1). Stress impeded the growth of plants, led to weight gain reductions in shoots as well as roots and hindered phosphorus and nitrogen uptake. However, salt‐stressed mycorrhizal plants produced greater root and shoot biomass, had higher phosphorus and nitrogen content than the corresponding uninoculated stressed plants. Salt stress resulted in higher lipid peroxidation and membrane stability was reduced in non‐AM plants. The presence of fungal endophyte significantly reduced lipid peroxidation and membrane damage caused by salt stress. AM plants maintained higher K⁺ : Na⁺ and Ca²⁺ : Na⁺ ratios than non‐AM plants under stressed and unstressed conditions. Salinity induced the accumulation of both proline and glycine betaine in AM and non‐AM plants. The quantum of increase in synthesis and accumulation of osmolytes was higher in mycorrhizal plants. Antioxidant enzyme activities increased significantly with salinity in both mycorrhizal and non‐mycorrhizal plants. In conclusion, pigeonpea plants responded to an increased ion influx in their cells by increasing the osmolyte synthesis and accumulation under salt stress, which further increased with AM inoculation and helped in maintaining the osmotic balance. Increase in the antioxidant enzyme activities in AM plants under salt stress could be involved in the beneficial effects of mycorrhizal colonization.     

Identification of two RAPD markers genetically linked to a recessive allele of a Fusarium wilt resistance gene in pigeonpea (Cajanus cajan L. Millsp.)

Summary Fusarium wilt (Fusarium udum Butler) is a soil borne disease of pigeonpea which causes substantial yield losses. The disease can occur at any stage of plant development, from the young seedling to the pod filling stage. Though resistance is simply inherited, transfer to locally adapted cultivars has been difficult due to linkage drag and difficulty in accurate phenotyping, except in sick plots. An attempt was made to identify RAPD markers associated with wilt phenotype by using F2 populations derived from contrasting parents; GSl (susceptible) ‘ICPL87119 (resistant) and GS1’ ICP8863 (resistant). Parents and F₂s were grown in a national _Fusarium sick-plot at Gulbarga, India and phenotyped as resistant or susceptible during the entire crop growth period. In both the crosses, resistance to wilt segregated as a monogenic dominant character. DNA samples extracted from sick plot grown, early seedling stage plants of parents and 254 F₂ plants of GS1 × ICPL87119 were held separately for marker identification. PCR reactions using 340 random decamer primers with genomic DNA of parents resulted in detection of 45 polymorphic amplicons from 39 primers. PCR testing of bulked DNA from subsets of resistant and susceptible plants revealed the presence of two amplicons at 704 bp and 500 bp (OPM03704 and OPAC11500) with susceptibility. Analysis of individual F₂ plants showed a segregation ratio of 3: 1 for the presence: absence of the amplicon in both crosses. Considering the wilt reaction and susceptibility-linked RAPD marker, it was possible to deduce genotype of every F₂ plant and the genotypic ratio for wilt reaction was 1RR: 2Rr: 1rr, as expected.     

Development of a <Emphasis Type="Italic">Cajanus cajanifolius</Emphasis>-based CMS Hybrid Technology in Pigeonpea

Pigeonpea is an important food legume of the semi-arid tropics grown mainly under subsistence agriculture. As a first step to address the five decades-long yield stagnation, a proof-of-concept for a commercially viable CMS-based hybrid technology with high standard heterosis and fertility restoration has been demonstrated. Six generations of backcrossing and selection for male sterility, and agronomic superiority using a Cajanus cajanifolius- (A₄ cytoplasm) based CMS donor (ICPA 2039) and a medium-maturity group recurrent parent ICPL 20176 (ICPB 2043) which resulted in a stable male sterile line (ICPA 2043) with near-perfect male sterility and superior agronomic traits. Following backcrossing and selections, the A-line (ICPA 2043) appeared to be morphologically similar in terms of various qualitative and quantitative traits compared to the B-line (ICPB 2043). However, differences between ICPA 2043 and ICPB 2043 were observed for days to maturity, 100-seed weight, pods plant^-1, and seed weight plant^-1. These differences may not be genetic but physiological. The best heterotic restorer line selected in a cross (ICPH 2671) combination restored a mean of 96.49% male fertility in 36 environments (12 locations, 3 years). Present investigation did not reveal significant G×E interaction for fertility restoration, indicating the possibility of obtaining high and stable grain yields in the pigeonpea growing areas of South and Central India.     

Identification of stable restorers and genetics of fertility restoration in late‐maturing pigeonpea [Cajanus cajan (L.) Millspaugh]

A total of sixty‐six germplasm lines were crossed with five CMS lines, where two belong to A₄ cytoplasm, while other three belong to A₂ cytoplasm. On the basis of pollen fertility test as well as good pod setting, of 330 hybrids, 34 restorer lines were observed in ICPA 2043 and 19 in ICPA 2092. Thirteen germplasm lines restored fertility in both the A₄ CMS lines, viz. ICPA 2043 and ICPA 2092; however, none of the lines restored fertility in A₂ CMS lines. For confirmation of result, restoration competence of identified lines tested subsequently 2 years at two different temperatures. The segregation patterns for fertility restoration studied in F₂ and BC₁F₁ generations of selected ten crosses. Six crosses indicated the involvement of two major genes with recessive epistasis, three crosses confirmed dominant epistasis, and one cross indicated the involvement of duplicate recessive epistasis. The obtained results from this study will hasten the future three‐line breeding programme and lead the hybrid technology to the farmers' field with the better exploitation of CMS lines.     

Detection and characterization of two new CMS systems in faba bean (Vicia faba) *

Wide crosses were made to identify new cytoplasmic male sterility (CMS) systems in faba beans, based on the interaction of cytoplasm with restorer and maintainer alleles. A total of 330 F₁ hybrids were produced in both reciprocal forms. Male sterile segregates were observed in one reciprocal version in the F₂ generation of six crosses. Two of these crosses with female parents originating from Afghanistan and Egypt expressed stable male sterility in subsequent backcross generations. Based on the female parents of the two crosses, these two CMS systems were designated CMS 199 and CMS 297. CMS 199 was more stable than CMS 297 during backcross generations and across different environments. Maintainer and restorer lines for both CMS systems were identified. Lower expression of male sterility occurred in CMS 297 in the greenhouse during the winter generations than in isolation cages during the summer generations, which may be utilized to maintain male sterile lines by selfing. Regarding practical applications, the CMS 199 shows great promise for hybrid breeding in faba beans.     

Inheritance and combining ability studies of pod physical and biochemical quality traits in vegetable pigeonpea (<Emphasis Type=Italic>Cajanus cajan</Emphasis> L. Millsp)

Pigeonpea (Cajanus cajan L. Millsp) is a popular vegetable crop in the Caribbean, grown for its immature green peas. Although breeding programmes, in the past, have made considerable strides in improving yield in a relatively photoperiod insensitive genetic background, the quality of peas continue to affect consumer acceptance. The mode of inheritance of a number of quality traits (physical and biochemical) known to affect consumer acceptance of pigeon peas was investigated in this study using a 6 × 6 half-diallel mating design and a M × N (5 × 6) mating design analysed using Griffing’s Method II Model I approach and the North Carolina design-II approach, respectively. The results showed that pod length, pod width, seeds per pod, shelling percentage and phenolic content were under the control of additive genetic effects with the non-additive effects generally being either not significant or much smaller compared to the additive genetic effects. Hundred seed weight was controlled by both additive and non-additive effects, while pod biochemical characteristics viz. sugar content, starch content and protein content, were governed by a preponderance of non-additive genetic effects. The strong genetic correlation between pod length, pod width and seed number indicates that these characteristics could be simultaneously improved in breeding programmes. The best general and specific combiners for the various characteristics were identified, and a method of improvement of quality in pigeonpea is discussed.     

Genetic analysis of yield and quantitative traits in pigeonpea (<Emphasis Type="Italic">Cajanus cajan</Emphasis> L. Millsp.)

Basic information on genetics and inheritance of quantitative characters, which is necessary to develop future breeding programme, is not widely studied in pigeonpea. Hence, present study was conducted among 5 generations in four pigeonpea crosses to know significance of additive-dominance model, gene action involved in inheritance of quantitative characters, heritability and genetic advance. “Scaling” and “joint scaling test” was significant for most characters indicating that additive-dominance model alone is not enough to explain the inheritance of a character. Though additive variance was more, dominance variance also played important role for most of the traits. Positive and negative alleles were found to be distributed between parents. Additive gene effect (d) was significant for pods per plant and seeds per pod whereas dominance gene effect (h) was more predominant among pod yield and seed yield. Dominance × Dominance inter-allelic interactions (l) was more important than Additive × Additive type (i) for most of the traits studied which could be exploited by selecting individuals based on their performance in recurrent selection. Complementary gene action was observed among many traits with few exhibiting duplicate gene action. Heritability and genetic advance was high indicating the effectiveness of selection. Since dominance effects is also present along with additive effects selection could be practised in later generations to identify high yielding genotypes.     

新型不育胞质在栽培稻中的分布与鉴定

为了分析只含有不育基因orf216在栽培稻中的分布,鉴定具有新的细胞质雄性不育胞质类型的种质资源。选取栽培稻824个品系为研究对象,以细胞质雄性不育相关序列HL-Sp1的特异引物进行PCR扩增,初步筛选得到9个候选品系,利用细胞质雄性不育基因orfH79,orf216的特异引物进行PCR扩增完成进一步筛选,并用Southern杂交验证。结果表明,最终筛选出IR72892,IR43,IR735463个只含有不育基因orf216不含orfH79的新型细胞质雄性不育胞质类型的品系。通过分子标记辅助选择,已成功的从824个栽培稻种中筛选到新的具有细胞质雄性不育胞质类型的新品系,为后续不育系的培育和相关理论研究奠定基础。     

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.     

植物CMS线粒体相关开放阅读框(ORFs)研究进展

从DNA、RNA、蛋白质水平分别阐述了线粒体开放阅读框(ORFs)与胞质雄性不育(CMS)的关系,并对目前发掘与胞质雄性不育相关的线粒体基因的研究策略进行了探讨.