Vector– New Large-Grain Rice Variety of Domestic Breeding

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Introduction
Rice is one of the valuable cereal crops cultivated on all continents, ranking second in terms of sown area after wheat, and in terms of gross grain yields it is equal to or even exceeds it in some years. Asia is the largest rice producer in the world, accounting for about 80% of the world's rice production [1,6,10].

Conditions, materials and methods of research
The agro-climatic conditions of Krasnodar region allow the cultivation of all rice varieties of domestic breeding and provide the crop with the necessary amount of heat. The sum of effective temperatures t°˃15 °С for the frost-free period is 1000-1200 °С at an average daily temperature of about 23 °С for the summer period. The climate of the region is temperate continental. Precipitation is short-term, showery in nature. During rice growing season, they fall about 350-360 mm. The predominant soil type in the experimental plot of FSBSI "Federal Scientific Rice Centre" is meadow-chernozem, weakly leached, lowhumus, heavy loamy on alluvial deposits. The humus content is 2.8-3.4%, gross nitrogen -0.19%, total phosphorus -0.16%, easily hydrolysable nitrogen compounds -6.1 mg / 100 g and exchangeable ammonium -0.78 mg / 100 g. Absorption capacity is low -32.0-34.0 mgeq./100 g of soil. The neutral reaction of the soil solution prevails, rarely weakly alkaline -pH = 7.2-7.6 [12,13].
The object of research was rice initial material, developed and studied in all stages of the breeding process at FSBSI "Federal Scientific Rice Centre". Variety VNIIR 10281 was selected from a variety of genotypes based on the results of previous years of research and studied in more detail in the period 2020-2022 under the conditions of competitive variety testing (CVT) on the rice irrigation system of Federal Scientific Rice Centre. Research work was carried out in accordance with the methods of experimental work on breeding developed at Federal Scientific Rice Centre and GOST 15.101.98 -"Procedure for the implementation of research work" [7,11].
For sowing experimental plots of competitive variety testing (CVT), a seeder with a Wintersteiger "Plotseed" central seeding machine was used. The plot area is 20 m2 (length 15 m, width 1.4 m), four times repetition, placement -randomized repetitions, standard variety -Favorit. The number of rows in a plot is eight, the distance between rows is 15 cm, the distance between plots is 40 and 50 cm. Mineral fertilizers N120P60K40 were applied to the soil before sowing, one dressing in the tillering phase with N46 urea. Predecessors by years of research are soybean, winter wheat and black fallow, respectively. Sowing dates -I-II decades of May.
Plants in the amount of 10 pieces from each repetition of all varieties were selected at full maturity to determine morphological characteristics and biometric analysis.
The results obtained were processed by the methods of variance and covariance analyzes [14].

Results and discussion
The most important traits characterizing new rice genotypes are grain yield and quality of final product (milled rice). However, it should be noted that they are quite complex, since they are due to a large number of simpler traits and properties that determine them, the variability of which largely depends on the agroclimatic and agrotechnical conditions of crop cultivation. Therefore, with the help of variance and covariance analyzes of the data, we revealed significant differences between the variants of our experiment in developing the large-grain rice variety Vector. The low variability of the main economically valuable traits indicates the high adaptability of the variety and the reliability of the results obtained (Table 1). It is well known that yield is the most important quantitative trait, prevailing over all others in its continuous methodological and analytical improvement. The table shows that the variety Vector during the years of study formed a yield higher than or equal to the standard, i.e. in 2020, a significant excess was revealed -8.8 t/ha. On average, over three years, the yield of the new variety was 9.13 t/ha with a low variability of the trait -3.3%. This is due to the maximum realization of the potential of panicle grain capacity, the number of productive stems with the duration of the growing season -124 days.
The calculation of the integral indicators that determine the yield -the productivity of one growing day and the grain content of agrophytocenosis, showed that the Vector accumulated 71.23 kg of dry matter / days / ha during the growing season, which is within the standard with an average grain content of agrophytocenosis -40.04 thous. pcs./m2. The variability of these traits is average -13.3 and 12.1%, respectively, due to the dynamism of the constituent elements (the duration of growing season, grain content of panicles, productive density and yield).
The total number of grains per panicle characterizes the yield potential of varieties and possible ways of its realization. The grain content of the variety Vector for three years averaged 150.7 pieces, which is 26.3 pieces higher than that of the standard. Hence, with almost the same grain sterility -17-18%, the new variety forms a larger number of grains. The average degree of variability of this trait -16.6% indicates the high adaptability of the variety Vector. It should be noted that the high grain content is a consequence of the increased panicle density. The density of the main panicle of variety Vector was 10.6 grains per 1 cm of the panicle, with an average length of 17.3 cm.
The mass of 1000 grains is one of the most important traits that characterize a variety, and is also a reliable criterion for belonging to a certain group according to grain size (short-grain, medium-grain and large-grain) [1,8]. In terms of grain size, the variety Vector should be attributed to the group of large-grain varieties with a mass of 1000 grains -34.5 g. The trait is slightly variable over the years -4.8%.
Total milling yield and head rice content are the main technological quality indicators that characterize economic efficiency of rice varieties during grain processing [9]. The variety Vector has high indicators of total milling yield and head rice content in the grain (according to ISO) -70,40 и 61,63 % respectively with a similar filminess and vitreousity. Low variability (< 10 %) of technological indicators of grain and mulled rice quality of new variety shows their stability.
An important aspect of the optimal combination of traits in one plant is the nature and closeness of their correlations. It is known that the relationship of economically valuable traits in different genotypes has its own specifics ( Table 2).  Qtrait; 1yield, t/ha; 2productivity of one growing day, kg/days/ha; 3grain content of agrophytocenosis, thous.pcs./m 2 ; 4plant height, cm; 5main panicle density, pcs./cm; 6total number of spikelets, pcs; 7mass of 1000 grains, g; 8vitreousity, %; 9filminess, %; 10total milling yield, %; 11head rice content (according to ISO), %.
Correlation analysis of the data revealed that the yield of variety Vector has a positive and close relationship with the productivity of one growing day of vegetation, grain content of agrophytocenosis, mass of 1000 grains, vitreousity and the total milling yield -0.975, 0.978, 0.890, 0.839 and 0.796, respectively. Hence, it should be assumed that in 95-63% of cases, conjugate traits are genetically determined. A similar picture is observed in the standard variety Favorit. Negative high correlation of yield with filminess and head rice content in the grain (ISO) --0.999 and -0.726, respectively, should be noted. From this it follows that an increase in yield above the optimum (8-9 t/ha) in 99 and 53% may lead to a decrease in grain and milled rice quality. Here, in variety Favorit, we observe a positive, but weak correlation with the head rice content -0.345. Table 2 shows that the plant height of new variety positively and closely correlates with the mass of 1000 grains and vitreousity -0.946 and 0.974. However, there was a close negative relationship with the head rice content --0.999, which may be a consequence of a similar correlation between plant height and grain filminess, but to a lesser extent --0.694, since the relationship of these quality indicators in 53% of cases is of a genetic nature. In the standard, the relationship of these traits is expressed weakly and in a different way.
It should be noted that in variety Vector, with a positive average degree of correlation of the total millng yield with the productivity of one growing day of and the grain content of agrophytocenosis -0.644 and 0.653, there is a negative close relationship of the latter with the head rice content --0.859 and -0.853. A close negative relationship of these integral yield indicators with filminess was also noted --0.975 and -0.978.
It has been established that the grain size of variety Vector closely and negatively correlates with filminess (-0.890) and head rice content in the grain (-0.960), and positively with vitreousity (0.995). This indicates a high degree of genetic determination of conjugated traits -79, 92 and 99%. In variety Favorit, the opposite nature of the relationship of these traits was noted.
Filminess has a close negative relationship with the total milling yield --0.796 and positive with the head rice content in the grain -0.726. In the standard variety, the nature of the relationship is similar.
Based on the results of a multi-year comprehensive assessment of new rice genotypes under the conditions of competitive variety testing, we have identified a promising largegrain variety Vector (VNIIR 10281), which was characterized in detail and transferred to SVT in 2022. Below is a description of a new rice variety, according to the generally accepted form of description.
Belongs to medium-late ripening group with a duration of growing period -121-124 days.
The leaves are medium dark green, intermediate in size, slightly pubescent. The flag leaf is of medium length and width, departing from the axis of the stem by 30-40°.
The panicle is compact, vertical, slightly spreading in the phase of full ripeness, 16-18 cm long, with a grain content of 185-195 spikelets and a density of 10-12 spikelets per 1 cm of length. The stalk of the panicle is of medium thickness, strong, protruding from the leaf sheath by 3-5 cm. The lemmas are straw-yellow in color, medium pubescent, without awns (Fig. 1).
Cooked rice is white, crumbly, the taste is good, water-uptake coefficient is 4.9-5.0, water absorption coefficient is 2.9. Grain is recommended for cooking garnishes, dishes of the Spanish and Italian cuisine (risotto, paella).
During the development of a new initial material and its further study, a promising largegrain rice variety Vector (VNIIR 10281) was identified, which has a high yield of 9.13 t/ha with its low variability of 3.3%. This is due to the ability of the variety to maximize the potential of the grain content of agrophytocenosis -40.01 thousand pieces / m 2 with the optimal duration of the growing season -124 days. The probability of genetic determination of these traits is 96%, with the degree of their positive correlation being 0.978.
The high level of stability and breeding value of variety Vector is ensured by its resistance to the main bio-and abiotic factors, and it also has a number of advantages in terms of some economically valuable traits. The new variety is characterized by a combination of relatively high indicators of the total milling yield and the head rice content in both milled rice and grains (70.4, 87.2 and 61.1%, respectively) with a mass of 1000 grains -34.5 g. However, a negative a close relationship between grain size and the head rice content (ISO) --0.960 is due to its similar correlation with filminess --0.890, since the probability of genetic determination of the last traits is 53% with their positive relationship -0.726.
Slight variability of the technological indicators of grain and milled rice quality of variety Vector -1.8-4.7% with a stable high yield is an important adaptive property both for its cultivation in various agro-climatic zones of Krasnodar region and neighboring Republics (Adygea, Dagestan, Chechnya) in order to increase gross yields, and for use in breeding programs as an initial material for development of large-grain forms (lines) with excellent taste and valuable culinary qualities.
According to the results of a multi-year comprehensive assessment, the medium-late ripening large-grain rice variety Vector, which optimally combines biometric and technological traits, was submitted in 2022 to the State Variety Test.