Analysis of Crop Genetic and Germplasm Diversity

Plant genetic resources are the basis for the genetic improvement of cultivated plants and future food and feed security [...]

From Classical Radiation to Modern Radiation: Past, Present, and Future of Radiation Mutation Breeding

Radiation mutation breeding has been used for nearly 100 years and has successfully improved crops by increasing genetic variation. Global food production is facing a series of challenges, such as rapid population growth, environmental pollution and climate change. How to feed the world's enormous human population poses great challenges to breeders. Although advanced technologies, such as gene editing, have provided effective ways to breed varieties, by editing a single or multiple specific target genes, enhancing germplasm diversity through mutation is still indispensable in modern and classical radiation breeding because it is more likely to produce random mutations in the whole genome. In this short review, the current status of classical radiation, accelerated particle and space radiation mutation breeding is discussed, and the molecular mechanisms of radiation-induced mutation are demonstrated. This review also looks into the future development of radiation mutation breeding, hoping to deepen our understanding and provide new vitality for the further development of radiation mutation breeding.

Unraveling Cuticle Formation, Structure, and Properties by Using Tomato Genetic Diversity

The tomato (Solanum lycopersicum) fruit has a thick, astomatous cuticle that has become a model for the study of cuticle formation, structure, and properties in plants. Tomato is also a major horticultural crop and a long-standing model for research in genetics, fruit development, and disease resistance. As a result, a wealth of genetic resources and genomic tools have been established, including collections of natural and artificially induced genetic diversity, introgression lines of genome fragments from wild relatives, high-quality genome sequences, phenotype and gene expression databases, and efficient methods for genetic transformation and editing of target genes. This mini-review reports the considerable progresses made in recent years in our understanding of cuticle by using and generating genetic diversity for cuticle-associated traits in tomato. These include the synthesis of the main cuticle components (cutin and waxes), their role in the structure and properties of the cuticle, their interaction with other cell wall polymers as well as the regulation of cuticle formation. It also addresses the opportunities offered by the untapped germplasm diversity available in tomato and the current strategies available to exploit them.

Frequent germplasm exchanges drive the high genetic diversity of Chinese-cultivated common apricot germplasm

The genetic diversity of germplasm is critical for exploring genetic and phenotypic resources and has important implications for crop-breeding sustainability and improvement. However, little is known about the factors that shape and maintain genetic diversity. Here, we assembled a high-quality chromosome-level reference of the Chinese common apricot ‘Yinxiangbai’, and we resequenced 180 apricot accessions that cover four major ecogeographical groups in China and other accessions from occidental countries. We concluded that Chinese-cultivated common apricot germplasms possessed much higher genetic diversity than those cultivated in Western countries. We also detected seven migration events among different apricot groups, where 27% of the genome was identified as being introgressed. Remarkably, we demonstrated that these introgressed regions drove the current high level of germplasm diversity in Chinese-cultivated common apricots by introducing different genes related to distinct phenotypes from different cultivated groups. Our results highlight the consideration that introgressed regions may provide an important reservoir of genetic resources that can be used to sustain modern breeding programs.

In situ conservation of traditional vegetable diversity in Wa homegardens in southwestern Yunnan, China

Background Homegardens are in situ conservation sources of germplasm diversity for overcoming homogenous germplasm problems in industrial agricultural systems. The Wa people constitute a long-dwelling ethnic group mainly in southwestern Yunnan with a unique culture and rich knowledge of traditional vegetables. We hypothesized that traditional vegetable varieties are well conserved in Wa homegardens because Wa culture promotes the preservation of traditional vegetables. We surveyed vegetable varieties and the practices that are involved in the conservation of traditional vegetables in Wa homegardens, which could form the basis for in situ conservation. Methods The methods were used including questionnaires and semi-structured interviews. Sixty homegardens were surveyed through purposive sampling in 6 Wa villages. We documented ethnobotanical information about vegetables in homegardens. Plant species were identified according to the Flora of China. And thematic analyses were conducted for in-depth interviews to identify the conservation factors for traditional vegetables. Results Fifty-two vegetable species belonging to 16 families and 41 genera were recorded from 60 Wa homegardens. Fifty-five traditional vegetable varieties and thirty-six hybrids were recorded. Among all the villages, 23 ± 6 (average ± SD) traditional vegetable varieties per homegarden and 9 ± 3 (average ± SD) introduced varieties per homegarden were recorded. Local seeds were stored in 78% of households, with an additional 9% of households’ seed supplies coming from neighbors and relatives; the other 13% of households purchased local seeds from markets. In 83% of families, the female head was mainly responsible for the decision-making concerning traditional vegetables in homegardens; in 10% of families, the male head was responsible for decision-making, and a small percentage (2%) was determined by elderly people. Five percent of families made decisions jointly between male and female household heads. Conclusions This study demonstrated that rich traditional germplasm diversity is harbored in Wa homegardens because of the unique culture and traditional knowledge of Wa communities, which are practiced daily with homegrown food plants. Local vegetable seed conservation and sharing systems help maintain germplasm diversity in the Wa community homegardens. Wa homegardens constitute a practical solution for protecting traditional germplasm diversity and maintaining traditional lifestyles.

Diversity, trait preferences, management and utilization of yams landraces (Dioscorea species): an orphan crop in DR Congo

BackgroundYam ( Dioscorea spp .) is cultivated in many villages of DR Congo as a means to sustain food security and alleviate poverty. However, the extent of the existing diversity has not been studied in details thus, considered as an orphan.MethodologyA survey covering 540 farmers in 54 villages was conducted in six major yam growing territories covering three provinces in DR Congo to investigate the diversity, management and utilization of yam landraces using pre-elaborate questionnaires.ResultsSubject to synonymy, a total of 67 landraces clones from five different species were recorded. Farmers’ challenges limiting yam production were poor tuber qualities (69%), harvest pest attack (7%), difficulty in harvesting (6%), poor soil status (6%). The overall diversity was moderate among the recorded yam germplasm maintained at the household level (1.32) and variability exist in diversity amongst the territories and provinces. Farmers’ in territories of Tshopo and Mongala provinces maintained higher level of germplasm diversity (2.79 and 2.77) compared to the farmers in territories of Bas-Uélé (1.67). Some yam landraces had limited abundance and distribution due to loss of production interest in many villages attributable to poisons contained hence, resulting in possible extinction. Farmers’ most preferred seed source for cultivation were backyard (43%) and exchange with neighboring farmers (31%) with the objective of meeting food security and generating income. In villages where yam production is expanding, farmers are relying on landraces with good tuber qualities and high yield even though they are late maturing.ConclusionThis study revealed the knowledge of yam genetic diversity, constraints to production and farmers’ preferences criteria as a guide for collection and conservation of yam genetic resources for yam improvement intervention.

In-situ Conservation of Traditional Vegetable Diversity in Wa Homegardens in Southwestern Yunnan, China

Background: Homegardens are recognized as in-situ conservation sources of germplasm diversity to overcome homogenous germplasm problems in the industrial agriculture system; it is crucial to understand how smallholders manage their homegardens to maintain traditional genetic resources. Wa is a long-dwelling ethnic group living mainly in southwest Yunnan, China. Traditional vegetables in homegardens management are still central to farmers’ livelihoods in Wa villages. We surveyed traditional vegetables in Wa homegardens and analyzed the factors conserving traditional vegetables in the homegardens management. Methods: The methods used in this work included semi-structured interviews, questionnaires, and field surveys. A total of 60 households through purposive sampling in three townships, 6 villages were surveyed. We documented ethnobotanical information on local name, edible methods, edible parts of traditional vegetables maintained in Wa homegardens. Plant species cultivated in Wa homegardens were identified according to Flora of China.Results: Fifty-five traditional vegetable varieties and 36 hybrid vegetable varieties in the homegardens were recorded. Among all the villages, 23 ± 6 (average ± S.D.) traditional vegetable varieties per homegarden and 9 ± 3 (average ± S.D.) introduced vegetable varieties per homegarden were recorded. 78% of households choose to store the local seeds themselves, with a further 9% of households’ seed supplies coming from neighbors and relatives, other 13% of households choose to purchase local seeds in the markets. In 83% of families, the female head holds the main responsibility for decision making for traditional vegetables planted in homegardens; in 10% of families were male head household to take responsibility for decision-making, and a small percentage which is 2% is determined by the elderly. 5% of families will make decisions jointly between both male and female household heads.Conclusions: This study demonstrated that rich traditional germplasm diversity is harbored in the Wa homegardens because of Wa communities’ unique culture and traditional knowledge, which is practiced daily using homegrown food plants. Local vegetable seed saving and sharing systems can help maintain the germplasm diversity in the Wa community’s homegardens. Wa homegardens can be a practical solution to protect the traditional germplasm diversity and maintain a lifestyle with traditional culture.

Gamma-ray induced pedigreed mutant population of tossa jute (Corchorus olitorius L.): a key resource for forward and reverse genetics.

Narrow genetic diversity in available germplasm is a serious limiting factor for academic progress and agronomic improvement of crops like Corchorus olitorius, an economically important bast fibre crop. Mutation breeding, with its proven ability to improve qualitative as well as quantitative traits, can be employed to augment germplasm diversity. In the present study, gamma-rays were used to treat the seeds of two promising varieties, JRO 204 and JRO 8432; LD50 doses for gamma-rays were 200 Gy and 300 Gy for JRO 204 and JRO 8432, respectively. Irradiation of two varieties has resulted in the development of a large number of macro-mutants, such as twisted bark, extreme dwarf, non-abscission leaf, soft stem, hard stem and round pod mutants. Morphological and anatomical studies of these mutants gave new light on secondary growth in the species. In addition to the academic utility, these mutants will prove of immense importance to plant breeders aiming to improve fibre quality. Moreover, novel mutants will help to develop new plant architecture suitable for diversified applications of the genus.

Insights into Marker Assisted Selection and Its Applications in Plant Breeding

Burgeoning the human population with its required food demand created a burden on ever-decreasing cultivated land and our food production systems. This situation prompted plant scientists to breed crops in a short duration with specific traits. Marker-assisted selection (MAS) has emerged as a potential tool to achieve desirable results in plants with the help of molecular markers and improves the traits of interest in a short duration. The MAS has comprehensively been used in plant breeding to characterize germplasm, diversity analysis, trait stacking, gene pyramiding, multi-trait introgression, and genetic purity of different cereals, pulses, oilseeds, and fiber crops, etc. Mapping studies pointed out several marker-trait associations from different crop species, which specifies the potential application of MAS in accelerating crop improvement. This chapter presents an overview of molecular markers, their genesis, and potential use in plant breeding.