The opposite arrangement of the leaves of the cucumber

Actuality. The opposite arrangement of the first two leaves in cucumber seedlings can be attributed to undesirable morphoses. The task was set: "To find out how often this sign occurs in cucumber seedlings and whether it is transmitted in the next generations during seed propagation."
Material and conditions. The research was carried out on the cucumber breeding material of the laboratory of selection and seed production of pumpkin crops (100-142 samples) on the basis of the Federal Scientific Vegetable Center in 2019-2021 in the Moscow region in the conditions of the seedling department of the winter greenhouse. Sowing of cucumber seeds for seedlings was carried out on January 10-13, March 15 and May 5. Seedlings were grown on racks in plastic pots with a 0.7 l peat mixture in accordance with the generally accepted cultivation technology. In winter – with additional illumination, in spring – without artificial illumination.
Results. From year to year, almost the same selection samples of cucumber had plants with the opposite arrangement of the first real leaves. These samples differed significantly in the number of plants with an unconventional arrangement of the first true leaves, but there were differences, sometimes very strong, between families of the same origin. All this suggests that the trait is genetically determined. When sowing cucumber seeds for seedlings on January 10-13, depending on the year of research and the genotype of the material used, from 18.3 to 25.6% of samples were identified that had plants with the opposite arrangement of the first and second true leaves. In seedlings for a spring heated greenhouse (sowing on March 15), there were about 15% of such samples, and 11.0% for non-heated ones (sowing on May 5). In general, the total number of plants with the opposite arrangement of real leaves in the first node was small and varied, depending on the growing conditions and the genotype of the studied samples, from 4.2 to 11.5% of the total number of studied plants. When sowing cucumber seeds at the same time, in the winter of 2019, compared to 2020 and 2021, there were 2.4 and 1.5 times more plants with the opposite arrangement of the first two real leaves. This can be explained by the fact that when planting seedlings, families with a large number of plants with opposite leaves were rejected. Weakened plants with opposite leaves within the family were also rejected. As a result, the material involved in further work had fewer plants with an unconventional arrangement of the first true leaves. It should be noted that plants with opposite leaf arrangement had only those F1 hybrids whose parent forms also differed in this disadvantage. It can be concluded that by selecting parent forms that do not have opposite leaf arrangement, it is possible to create hybrids that will not react sharply to the deterioration of growing conditions by laying opposite leaves.

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