In contemporary biological breeding, species propagation, and ecological germplasm cultivation, a one-sided and deeply entrenched consensus has long been solidified: hybridization equals advantage, crossbreeding equals improvement, and inter-varietal fusion equals evolutionary upgrade. Whether in crop breeding, livestock improvement, or certain population optimization studies, the vast majority of research and practical applications blindly pursue hybrid combinations. The mixing of genes from different varieties, strains, or even closely related species is regarded as the sole shortcut to enhancing biological traits, strengthening viability, and achieving genetic iteration. This one-dimensional cognition has long dominated the field, while deliberately avoiding the most fundamental laws of genetics and ignoring the irreversible genetic risks posed by blind, disorderly hybridization. Based on the principles of random genetic recombination, the logic of germplasm resource conservation, and empirical evidence from biological propagation, this paper thoroughly refutes the scientific fallacy that "hybridization necessarily produces advantage." It establishes a brand-new core concept for breeding: pure germplasm as the foundation, controlled hybridization as a tool, and inferior hybrids as must-be-eliminated. This framework reshapes the underlying logic of biological propagation and germplasm protection.

1. The Probabilistic Nature of Genetic Recombination

The essence of genetics has never been "fusion equals improvement," but rather the probabilistic, bidirectional outcome of gene combination. This is the unshakable objective fact underlying all biological reproduction and varietal evolution, and it is the core scientific basis for overturning the myth of hybridization as a panacea. The key traits, immune resistance, growth stability, and reproductive viability of any biological variety are determined by the population's core advantageous gene clusters, purified over generations through selective propagation. Hybridization between different varieties or strains is essentially a random recombination process between two differentiated gene pools; there is no pre-set "automatic superposition" of advantages. Genetic recombination has no inherent tendency toward directed optimization. It has only two possible outcomes:

· Optimization: The complementary aggregation of advantageous genes. The favorable traits for stress resistance, high yield, and healthy reproduction from both parents are orderly combined, producing high-quality offspring with heterosis.
· Degradation: The superimposed amplification of deleterious genes. The recessive pathogenic genes, immune defects, and trait degradation genes latent within both parents couple with each other, giving rise to frail, immunodeficient, reproductively declined, congenitally defective inferior hybrid offspring.

2. Empirical Evidence of Hybrid Degradation

These two outcomes follow the natural laws of random probability. Superior varieties are never automatically harvested simply by performing a hybridization operation. Numerous cases in practical breeding demonstrate the backfiring effects of inferior hybridization. The most representative examples are the cross-species hybrids, ligers and tigons. Although these hybrid individuals appear large and unique in form, their genetic defects fully erupt: congenital immune system hypoplasia, disease resistance far below that of native lion and tiger populations, high rates of organ malformation, and drastically shortened lifespans. Moreover, they completely lack natural reproductive capacity. They are classic examples of hybrid degradation. The mule, produced by crossing horses and donkeys, is another example. Although mules possess the single advantage of draft labor, they permanently lack reproductive ability—a case of restrictive hybrid degradation where population sustainability is sacrificed for a narrow function. Similar phenomena exist in crop breeding. In some regions, blind backcrossing and disorderly intercrossing of high-yield hybrid crops have led to plummeting pest and disease resistance, degradation of stable yield traits, and a progressive decline in germplasm quality across generations. This fully confirms that hybridization is a double-edged sword: it can either optimize or degrade, and it is by no means a universal panacea.

3. The Myth of Hybridization as an End in Itself and the Loss of Germplasm

The long-standing industry-wide blind worship of hybridization and neglect of pure variety value stems from a core misunderstanding: treating hybridization as the goal of breeding rather than as a tool. This inversion of priorities has resulted in the irreversible loss of global germplasm resources. Numerous breeders and researchers blindly pursue short-term trait novelties from hybridization, striving for the number of new varieties and superficial improvements, while continuously compressing the conservation space for core pure germplasm. Countless native single varieties, purified over decades or centuries, are gradually moving toward varietal homogenization and germplasm extinction due to unplanned, blind hybridization that dilutes genetic purity and degrades trait foundations. Data from China's crop germplasm resource surveys have confirmed this severe current situation. Across many regions, native local characteristic crop varieties and high-quality livestock strains have seen sharp declines in core pure populations due to long-term unplanned and blind hybrid improvement. Some rare native germplasms are on the verge of complete extinction. Once the native pure gene pool disappears, any subsequent high-quality hybrid breeding or iterative variety improvement will become water without a source, a tree without roots.

4. Conclusion: Pure Germplasm as the Strategic Reserve

A core scientific principle must be clearly established: The pure single variety is the strategic gene reserve for all biological breeding and the foundational prerequisite for all high-quality hybrid improvement. Without pure variety conservation, there is no breeding sustainability. Pure varieties, through generations of natural selection and directed artificial purification, possess stable gene sequences, constant trait expression, high identifiability of advantageous vs. deleterious genes, and controllable population propagation patterns. They can consistently transmit superior core traits, clearly identify recessive deleterious genes, and serve as the essential raw material for scientific hybridization and directed breeding. Retaining pure single varieties is not an act of conservatism or a rejection of variety improvement; rather, it is about safeguarding the security baseline and genetic foundation of biological breeding. Maintaining varietal genetic purity is not about excluding genetic optimization; it is about retaining the core germplasm leverage for controlled, directed, and merit-based hybridization. If pure germplasm conservation is abandoned, and all varieties are allowed to undergo disorderly hybridization and chaotic gene fusion, the ultimate outcome will be genetic homogenization across all varieties, dilution of all superior traits, and spread of all deleterious genes. At that point, neither high-quality pure varieties for breeding nor high-quality hybrids for improvement will remain. The industry will fall irreversibly into a vicious cycle of breeding collapse.

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