Screening of 8 New Virus-Free Potato Lines

1 Materials and Methods

1.1 Experimental Materials A total of 9 new virus-free potato lines were used in the test, all introduced from the Bijie Region Potato Breeding and Virus-Free Center. Their line numbers were: B9904-2, B9904-1, B9901-33, B9911-1, B9911-3, B9907-4, B9910-9, BP26, and Mira (CK).

1.2 Experimental Methods The test was conducted on the contracted land of farmer Chen Guangyi in Fengshan Village, Fengshan Township, Dafang County, at an altitude of 1682 m, with flat terrain and medium fertility; the previous crop was @#@245@#@. Before sowing, the soil was plowed and broken up, and the land preparation quality met the test requirements. The test was monoculture, arranged in a single-factor randomized complete block design, with 3 replications and 27 plots. The plot area was 13.28 sq m, with a plot length of 4 m and width of 3.32 m, row spacing of 0.66 m, and hill spacing of 0.25 m. Each plot had 5 rows, with 16 hills per row, totaling 80 hills per plot, equivalent to 60,000 hills per hectare.

The test was sown on March 2, 2006, by digging hills and planting one whole tuber per hill (25-30 g). Per hectare, 22,500 kg of farmyard manure and 375 kg of potato-specific compound fertilizer were applied as base fertilizer, with no topdressing. After sowing, soil was covered and ridges were formed. After full seedling emergence, on May 13, earthing up was carried out together with intertillage and weeding.

2 Results and Analysis

2.1 Yield Table 1 shows that among the tested lines, the yields of 4 lines, B9904-1, B9904-2, B9901-33, and B9910-9, were higher than that of the control Mira, with yield increase rates of 25.85%, 17.42%, 13.70%, and 10.64%, respectively; the yields of 4 lines, B9911-3, B9911-1, BP26, and B9907-4, were lower than that of the control Mira, with yield reduction rates of 0.74%, 5.72%, 8.00%, and 10.84%, respectively. Analysis of variance showed that the yield increases of B9904-1 and B9904-2 over the control reached the 0.01 significant level and the 0.05 significant level, respectively. The yield differences between the remaining lines and the control were not significant.

2.2 Seedling Emergence Dynamics Table 2 shows that all 3 replications of the control Mira had complete seedling emergence, with an emergence rate of 100%; for B9904-2 and B9910-9, one plot each had complete seedling emergence, while the remaining test plots showed missing hills to varying degrees.

2.3 Growth Period Table 3 shows that for the number of growth days from sowing to emergence, the control Mira and BP26 were the same, B9910-9 was 17 d earlier than the control Mira, and the remaining lines were 7 d later than the control Mira. In terms of growth days from emergence to maturity, the control Mira and BP26 were the same, B9910-9 was 11 d earlier than the control; B9904-2 and B9911-1 were the same, 12 d later than the control; B9901-33 was 9 d later than the control; B9911-3 and B9907-4 were the same, 8 d later than the control; and B9904-1 was 4 d later than the control.

2.4 Main Underground Traits (Table 4)

2.4.1 Large and Medium Tuber Rate. Among the tested lines, except for B9911-1, which was lower than the control Mira, all other tested lines had a higher large and medium tuber rate than the control Mira.

2.4.2 Starch Content. Among the tested lines, 4 lines, BP26, B9907-4, B9911-3, and B9910-9, had higher starch content than the control Mira; the other 4 lines were all lower than the control Mira.

2.4.3 Average Number of Tubers per Plant. Among the tested lines, except for B9911-3, which had more than the control Mira, all other tested lines had a lower number of tubers per plant than the control Mira.

2.4.4 Average Yield per Plant. Among the tested lines, B9911-3 was the same as the control Mira, and B99011-1 and B9907-4 were lower than the control; the other 5 tested lines were all higher than the control Mira.

2.4.5 Tuber Shape and Skin Smoothness. In terms of tuber shape, the control Mira was long cylindrical; the 3 lines B9904-2, B9904-1, and B9901-33 were long elliptical; B9911-1, B9911-3, and BP26 were round; and B9907-4 and B9910-9 were oblate. In terms of skin, B9904-2, B9907-4, and BP26 had netted skin, the control Mira was relatively rough, and the remaining tested lines all had smooth skin.

2.4.6 Skin and Flesh Color. Among the tested varieties (lines), except for B9904-1, B9901-33, B9911-1, and B9910-9, whose skin color was light yellow, all other tested varieties (lines) had yellow skin. In terms of flesh color, B9911-3 was light yellow, B9901-33, B9911-1, and BP26 were milky white, and all other tested varieties (lines) had yellow flesh.

2.4.7 Eyes. The number of eyes was medium in the control Mira, while all other tested lines had fewer eyes than the control Mira. Eye depth was deep in the control Mira, medium in B9907-4, and shallow in all other tested lines.

2.5.1 Plant Shape and Flower Color. The plant shape of B9911-3, B9907-4, and the control Mira was semi-erect, while the other tested lines were erect. Except for the 3 lines B9904-1, B9911-1, and B9911-3, which did not flower, all other varieties (lines) had white flowers.

2.5.2 Plant Height and Stem Thickness. The control Mira had a plant height of 89.4 cm and a stem thickness of 0.6 cm; all tested lines had greater plant height and stem thickness than the control Mira.

2.5.3 Number of Main Stems and Branches. The number of main stems was 4.2 for BP26 and the control Mira. Among the other tested varieties (lines), except for B9907-4, which had 6.2 and was higher than the control Mira, all other lines had fewer main stems than the control. All tested lines had more branches than the control Mira.

2.6 Disease Situation During the entire test period, only leaf roll disease, late blight, and powdery scab occurred (Table 6).

2.6.1 Leaf Roll Disease. In the field, except for B9904-1, which had leaf roll disease with a diseased plant rate of 2.5%, none of the other tested varieties (lines) had leaf roll disease.

2.6.2 Late Blight. In the survey on June 30, only the two lines B9904-1 and B9911-1 had no diseased plants; all other varieties (lines) had late blight to varying degrees, among which the control Mira had the most severe incidence, with a disease grade of 3 and an incidence rate of 100%; the other lines all had a disease grade of 1, and the incidence rates were 90% for B9911-3, B9907-4, B9910-9, and BBP26, 80% for B9904-2, and 50% for B9901-33. In the survey on July 7, the highest disease grade was 3 for the control Mira, followed by 2 for B9901-33 and B9911-3, and 1 for all other lines; for incidence rate, except for B9904-1 and B9907-4, which were 80.0% and 90.0%, all other lines had an incidence rate of 100.0%.

2.6.3 Powdery Scab. Among the tested varieties (lines), B9904-2, B9911-1, B9907-4, BF26, and the control Mira did not develop powdery scab, while the remaining lines all had mild powdery scab.

3 Characteristics of the Tested Varieties and Recommendations

3.1 B9904-1 Its yield ranked 1st among the tested varieties (lines), with a plot-equivalent yield of 420482 kg/ha, reaching the 0.01 extremely significant level of yield increase over the control Mira, with a yield increase rate of 25.85%. The tubers were long elliptical, with light yellow skin, yellow flesh, few and shallow eyes, smooth skin, relatively late occurrence of late blight, and mild powdery scab. It is recommended for participation in regional trials and for organizing production tests.

3.2 B9904-2 Its yield ranked 2nd among the tested varieties (lines), with a plot-equivalent yield of 392319 kg/ha, reaching the 0.05 significant level of yield increase over the control Mira, with a yield increase rate of 17.42%. The tubers were long elliptical, with yellow skin and yellow flesh, few and shallow eyes, smooth skin, and resistance to powdery scab. It is recommended for participation in regional trials and for organizing production tests.

3.3 B9911-3 Its yield ranked 3rd among the tested varieties (lines), with a plot-equivalent yield of 37989.5 kg/ha, 13.70% higher than the control Mira. Its large and medium tuber rate was 91.28%, ranking 1st and 23.55% higher than the control. The tuber shape was long elliptical, with light yellow skin, milky white flesh, smooth skin, and few and shallow eyes. It is recommended to continue identification.

3.4 B9910-9 Its yield ranked 4th among the tested varieties (lines), with a plot-equivalent yield of 36965.4 kg/ha, 10.64% higher than the control Mira. The tubers were oblate, with light yellow skin, yellow flesh, few and shallow eyes, and smooth skin. It is recommended to continue identification.

3.5 Other Varieties The yields of the other varieties were all lower than that of the control Mira. Because this test was conducted for only 1 year, and there was early drought that year, followed by rainy weather in mid-to-late June, the field humidity was relatively high. In order to correctly evaluate the "three traits" of the new potato lines in Dafang County, it is recommended to continue the test the following year.