Gene action and combining ability estimates using cytoplasmic-genic male sterile lines to develop pigeonpea hybrids for rainfed condition

Pigeonpea is the major source of vegetable protein in Indian diet. About 72.5 percent area and 62.5 production of world’s pigeonpea is in India.Pigeonpea is the only food legume where cytoplasmic-genic male sterility is being exploited for commercial use of hybrids. The discovery of stable CMS system and breeding of commercial hybrids in pigeonpea has become a landmark in increasing the productivity of this crop. Keeping in view the combining ability estimates were worked out through Line x Tester analysis of 10 hybrids developed by crossing 2 lines (Males) with five cytoplasmic male sterile (CMS) lines (Females) to know the genetic architecture of yield attributesDays to maturity, branches plant1 , pods plant1 , seed yield, wilt resistance and pollen fertility. Analysis of variance revealed significant differences among genotypes, crosses, lines, testers and Line x tester interactions for most of the traits. Preponderance of non-additive gene action was realized by higher values of specific combining ability compared to general combining ability. The average degree of dominance were more than unity (>1) and predictability ratio was less than unity (<1) for all the traits, signifying non-additive gene action resulted from dominance, over dominance, epistasis and various other interactions. Hence, heterosis breeding is effective for increasing yield potential of hybrids in pigeonpea.The proportional contribution of testers was observed to be lower than that of line x tester interactions, thus highest estimates of SCA variances. The estimates of GCA effects indicated male parent ICPL 87119 was good general combiner for days to maturity and pollen fertility and among the female parent ICP 2043 was good general combiner. Cross combinations ICP 2043 x ICP 87119, ICP 2048 x ICP 20108, ICP 2078 x ICP 87119 and ICP 2092 x ICP 20108 were found to be good specific combinations for seed yield plant1 and other desirable traits

Challenges and opportunities of breeding early maturing pigeonpea hybrids

Recently, a hybrid breeding technology has been successfully developed in pigeonpea and three high yielding hybrids were released. This technology is based on cytoplasmic -nuclear male-sterility (CMS) and insect-aided natural out – crossing systems. These hybrids produced 25–40% more yield over the local cultivars in farmers'fields. The seed production technology of hybrids and their male and female parents has also now been perfected. These hybrids mature in 6–7 months hence have limited adaptation; to register greater impact of this technology early maturing (4–5 months) group hybrid breeding programme was initiated. This paper, besides reviewing the performance of some early maturing hybrids, discusses their prospects in enhancing productivity in the existing and new potential niches

Developing improved varieties of pigeonpea

By 2050 the world population is likely to reach nine billion, with most of the increase in the semi-arid tropics where many of the world’s poor reside. It has been estimated that this will require a 70% increase in food production (Alexandratos and Bruinsma, 2012). Increasing food production to this extent in the face of looming climate changes, decreasing water resources, escalating production cost and limitation of arable land will be a Herculean task. In this context, a food legume, popularly called as pigeonpea (Cajanus cajan (L.) Millsp.), red gram (tuar) or yellow lentil, could play a significant role in providing food and nutritional security. This is possible because this crop has potential to grow well in warmer conditions with limited water and inputs..

Advances in Pigeonpea Genomics

Pigeonpea, a member of family Fabaceae, is one of the important food legumes cultivated in tropical and subtropical regions. Due to its inherent properties to withstand harsh environments, it plays a critical role in ensuring sustainability in the subsistence agriculture. Furthermore, plasticity in the maturity duration imparts it a greater adaptability in a variety of cropping systems. In the post genomics era, the importance of pigeonpea is further evident from the fact that pigeonpea has emerged as first non-industrial legume crop for which the whole genome sequence has been completed. It revealed 605.78 Mb of assembled and anchored sequence as against the predicted 833 Mb genome consequently representing 72.8 % of the whole genome. In order to perform genetic and genomic analysis various molecular markers like random amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), simple sequence repeat (SSR), diversity array technology (DArT), single feature polymorphism (SFP), and single nucleotide polymorphism (SNP) were employed. So far four transcriptome assemblies have been constructed and different sets of EST-SSRs were developed and validated in a panel of diverse pigeonpea genotypes. Extensive survey of BAC-end sequences (BESs) provided 3,072 BES-SSRs and all these BES-SSRs were further used for linkage analysis and trait mapping. To make the available linkage information more useful, six intra-specific genetic maps were joined together into a single consensus genetic map providing map positions to a total of 339 SSR markers at map coverage of 1,059 cM. However, earlier very few linkage maps were available in the crop because of non-availability of genomic resources. Several quantitative trait loci (QTLs) associated with traits of agronomic interest including QTLs for sterility mosaic disease, fertility restoration, plant type and earliness have been identified and validated. To strengthen the traditional breeding, plenty of genomics tools and technologies are now available for integration in regular pigeonpea breeding schemes. This article presents the progress made in the area of pigeonpea genomics and outlines its applications in crop breeding for pigeonpea improvement

Recent advances in Pigeonpea [Cajanus cajan (L.) Millspaugh) Research

Pigeonpea or red gram [Cajanus cajan (L.) Millspaugh] is an important food legume of the semi-arid tropics of Asia and Africa. It occupies a prime niche in sustainable farming systems of smallholder rainfed farmers. It occupies a prominent place in Indian rainfed agriculture. It is an integral component in various agro ecologies of the country mainly inter cropped with cereals, pulses, oilseeds and millets. It is the second most important pulse crop next to chickpea, covering an area of around 4.42 m ha (occupying about 14.5% of area under pulses) and production of 2.86 MT (contributing to 16% of total pulse production) and productivity of about 707 kg/ha. It is mainly consumed as dry split dhal throughout the country besides several other uses of various parts of pigeonpea plant. Enhancing the productivity of the crop assumes specific significance in India mainly to combat protein malnutrition as it is the main source of protein to the predominant vegetarian population. The productivity of pigeonpea has remained low and stagnant over the last few decades thus this prompted scientists to search for novel ways of crop improvement. To tackle this challenge, ICRISAT and IIPR are working on number of innovative ideas like, genome sequencing (Varshney et al. 2012), development of CGMS hybrids with 30 to 40 % yield advantage over traditional varieties, development of photo insensitive super early maturing lines, introgression of cleistogamous flower structure to maintain genetic purity of elite lines, use of obcordate leaf shape as NEP to assess genetic purity of hybrid parental lines and development of disease resistant hybrids and elite breeding lines. These aspects are described briefly in this paper..

Pigeonpea Seed Production System of Smallholder Farmers: An Assessment in Odisha, India

Smallholder pigeonpea farmers in Odisha always rely on self-saved seeds of preferred landrace with long maturity period of 7 months and exploiting this for a period of 2-4 years or more. These model of seed system continuously resulted in low yield (250-500 kg/ha) due to seed deterioration. Seed production at farmers’ level with the provision of new package of technology such as providing farmers preferred high yielding varieties and hybrids, on the ground training on cultural production and management, and integrated pest and disease management has contributed in increase in productivity (780 kg/ha), improving livelihood, and income of farmers in the project sites (Rayagada, Kalahandi, and Nauparha). Institutionalizing the seed system model through the ‘one village one variety’ concept has brought about the production of 1610 tons of various certified seeds. The assessment also revealed that higher investment in seed production resulted in higher seed yield and income. Likewise, farmers seed growers with medium land classification showed the best B;C ratio with Rs 3.38 per Rs 1 invested. Moreover, it can be deduced from the B:C ratio of all land classification that seed production is economically viable for smallholder farmers to venture in improving their livelihoods. However, there are still limitations that needs to be addressed to ensure the sustainability of the seed delivery system of the project. The most pressing constraint of pigeonpea production is the damage caused by pests and diseases and the lack of farm inputs; trainings/awareness meetings/exposures are required to educate farmers on new pigeonpea technologies; and the need to regulate prices of pigeonpea seeds is a major concern for smallholder farmers to obtain benefit from their pigeonpea cultivation

Tropical Legumes 2 pigeonpea seed system in India: An analysis

Pigeonpea farmers in India have historically relied on selfsaved seed of local varieties as their seed source for upcoming growing seasons. As improved varieties for disease resistance and yield have been consistently developed, the challenges have been to help farmers gain and retain access to these improved varieties. The above objectives were tried to be accomplished through improved agronomic practices, promoting the seed village concept to minimize the effects of out-crossing, and developing local seed production capacity under the aegis of the Bill Melinda Gates Foundation funded Tropical Legumes 2 (TL 2) project operational with the pigeonpea farmers for the last 4 years. The project was implemented in Tandur, Ranga Reddy District of Andhra Pradesh, India, a region where the pigeonpea is cultivated as monocropped or intercropped with other crops. Ahandful of farmers have become truthfully labeled seed producers, but educational programmes and improved seed have not yet reached the majority of individuals in the communities targeted, creating a gap both in understanding and in meeting project goals. Small hold farmers because of their subsistence level are usually not involved in seed production. However, improved varieties should be made available to them for meeting the above objectives. The focus on continuing increasing opportunity for small holders through seed system improvement would yield more innovative methods for community involvement and accessibility so that the gaps in understanding can be bridged up for the welfare of the society as a whole

Strategies for pigeonpea improvement

In order to feed an ever-increasing population, it is essential to deal yieldreducing factors. Climate smart crop varieties that yield more with fewer inputs will be required to achieve the success. In this scenario pigeonpea plays an important role as it can stand in relatively harsh environmental conditions. Hybrid breeding along with the pure line breeding, genetic resources and genomics advances are enriching this crop. However, the pigeonpea improvement program must be re-oriented in order to deal with the yield-reducing factors and to break the yield plateau

Characterization and mapping of Dt1 locus which co-segregates with CcTFL1 for growth habit in pigeonpea

Pigeonpea (Cajanus cajan) is one of the most important legume crops grown in arid and semi-arid regions of the world. It is characterized with few unique features compared with other legume species, such as Lotus, Medicago, and Glycine. One of them is growth habit, an important agronomic trait. In the present study, identification of mutations affecting growth habit accompanied by a precise analysis of phenotype has been done which will shed more light upon developmental regulation in pigeonpea. A genetic study was conducted to examine the inheritance of growth habit and a genotyping by sequencing (GBS)-based genetic map constructed using F2 mapping population derived from crossing parents ICP 5529 and ICP 11605. Inheritance studies clearly demonstrated the dominance of indeterminate (IDT) growth habit over determinate (DT) growth habit in F2 and F2:3 progenies. A total of 787 SNP markers were mapped in the genetic map of 1454 cM map length. Growth habit locus (Dt1) was mapped on the CcLG03 contributing more than 61% of total phenotypic variations. Subsequently, QTL analysis highlighted one gene, CcTFL1, as a candidate for determinacy in pigeonpea, since an Indel marker derived from this gene co-segregated with the Dt1 locus. Ability of this Indel-derived marker to differentiate DT/IDT lines was also validated on 262 pigeonpea lines. This study clearly demonstrated that CcTFL1 is a candidate gene for growth habit in pigeonpea and a user-friendly marker was developed in the present study which will allow low-cost genotyping without need of automation