Variety Trials - 03



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Project Leader and Principal UC Investigators

James E. Hill, UCCE specialist, Dept. of Agronomy and Range Science, UC Davis


Sixteen on-farm rice variety evaluation trials were conducted throughout the rice-growing regions of California in 2003 by UC Cooperative Extension in collaboration with public and private plant breeders. These trials perform an essential role in exposing standard, advanced and preliminary varieties to a range of environments, cultural practices and disease levels.

Six similar tests were conducted at the Rice Experiment Station - two from each maturity group. Average yields across varieties and locations in the advanced line tests ranged from 8,610 pounds/acre in the very early trials to about 9,080 pounds/acre in the early tests. Unlike the dry, warm planting season of 2002, last year's planting time was exceptionally wet and thus late - not in total rainfall, but in the number and spacing of rainy days that delayed planting. Thus, the intermediate and late varieties yielded less than the early varieties in 2003.

As in previous years, the commercial standards ranked high in yield against the advanced and preliminary entries, demonstrating that yield advances are difficult to attain. That was particularly true with

M-205 in both the early and intermediate/late tests and S-102 in the very early tests. However, several advanced lines in 2003 produced very high yields and represent other important breeding objectives such as blast tolerance. Testing advanced and preliminary lines under a variety of conditions remains a critical aspect of releasing varieties adapted to changing cultural practices, markets and pests.

A replicated rice variety strip trial compared M-206 with M-103 and M-104 in the cool area of San Joaquin and Stanislaus counties.

Very Early Tests

Nine advanced breeding lines and eight commercial varieties were compared in four very early advanced tests. Additionally, 34 cultivar lines were tested in the preliminary trials at each location.

Grain yield in the advanced tests averaged 8,660 pounds/acre at RES, 8,500 pounds/acre at San Joaquin, 8,300 pounds/acre at Sutter and 9,000 pounds/acre at Yolo. Over the four locations, the highest yielding entry on average was the advanced long grain 02-Y-045 at 9,240 pounds/acre, followed by short grains S-102 (9,190 pounds/acre), experimental 00-Y-170 (8,970 pounds/acre) and advanced premium quality 01-Y-185 (8,940 pounds/acre). Other top-yielding commercial varieties included L-205, M-206, L-204 and M-202.

In spite of late planting, the time to reach 50 percent heading was 10-12 days less than in 2002 because of a prolonged stretch of plus-100 degree days last summer. The heat may also have been to blame for an increased amount of lodging in all four locations.

Over a five-year period and across locations, S-102 was the highest yielding variety, followed by M-104.

Early Tests

Nine advanced lines and 10 commercial varieties were compared in four early tests. Thirty-four preliminary lines were also evaluated in separate tests at each location.

Yields in the advanced lines averaged 9,080 pounds/acre at RES, 7,560 pounds/acre at Butte, 8,270 pounds/acre at Colusa and 8,020 pounds/acre at Yuba. The advanced medium grain 01-Y-617 was the highest-yielding entry averaged over the four locations at 9,240 pounds/acre. Other fairly consistent high yielders were M-205, 01-Y-327, 01-Y-327, 01-Y-655 and 99-Y-041.

Days to 50 percent heading ranged from 77 at RES to 84 at Colusa, a heat accelerated maturity in the same range as the very early tests (10-12 days).

Over a five-year period and across locations, M-205 was the highest yielding commercial variety at 9,130 pounds/acre, followed by M-204 at 8,931 pounds/acre.

Intermediate to Late tests

Eight advanced lines and six commercial varieties were compared in three intermediate-to-late tests. Twenty preliminary lines were also evaluated in separate tests at each location.

Yields in the advanced lines averaged 9,420 pounds/acre at RES, 7,580 pounds/acre at Glenn and 9,560 pounds/acre at Sutter, down on average from 2002 from the weather-related shorter growing season. M-205 was the highest yielding commercial entry at Sutter and, in the over-location average, was not significantly different from the top-yielding experimental entries.. L-205 and M-202 were the next highest yielding commercial entries. The highest yielding entry over both the advanced and preliminary lines was the medium grain cultivar 02-Y-382 at 10,060 pounds/acre.

Days to 50 percent heading ranged from 84 at RES to 87 at Sutter, which was three to nine days less than in 2002. Intermediate to late tests are planted earlier than the other maturity groups and were thus at a more advanced stage of development when high summer temperatures hit.

Over a five-year period and across locations, M-202 has been the highest yielding commercial variety in this group at 8,932 pounds/acre, with M-205 and M-204 close behind.

Nitrogen management study

This project also examines cultural practices associated with existing and upcoming varieties. One test conducted in 2003 evaluated nitrogen management in dry-seeded rice. This test clearly showed that nitrogen fertilizer should be managed differently in dry-seeded rice. Preplant nitrogen can be easily oxidized during periods when the soil is allowed to dry and lost in gaseous form when soil is reflooded. Thus nitrogen efficiency can be increased by a combination of split applications, part preplant and part topdressed immediately prior to permanent flood. In this test, nitrogen applied at panicle initiation was too late to affect yield.


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