ABSTRACT
Straighthead disease is a physiological disorder in rice and the most
widespread non-fungal disease of the U.S. straighthead greatly reduces rice
yield. Straighthead studies were most conducted in the artificial field which was
Arsenic amendment plots due to the similarity of straighthead symptoms of
Arsenic damage. To evaluate the straighthead disease resistance in natural
condition, 46 rice lines, including 24 inbred lines and 22 hybrid combinations which
were developed from breading program, were chosen for straighthead and agronomy
characters testing in a native soil where straighthead naturally induced in the
past years at University of Arkansas at Pine Bluff (UAPB), Arkansas in 2011 and
2012. The straighthead of rice were rated from 0 to 9 levels, and 0 was the least
straighthead disorder and 9 was the most severe straighthead disorder. Cocodrie
(CCDR) was used as the check in this study. The results of 2011 showed that the
yields of 8 entries were higher than the check CCDR. The straighthead scores of
these 8 entries were 0 - 1 which indicated their resistance to straighthead.
The rest of the entries had lower yields than check CCDR with straighthead
scores 5 - 6 which indicated their moderate susceptibility to straighthead. The
yields were negatively related to the straighthead scores (r = -0.9178, P < 0.01). The results of 2012 showed that the
yields of 9 hybrids and 6 inbred entries were higher than the check CCDR. The
straighthead scores of top 12 entries were 0 - 2 which indicated that they were
resistant to straighthead and 3 entries with straighthead score of 3 which indicated
they were moderately resistant to straighthead. The rest 3 hybrids and 4 inbred
entries had lower yields than the check and their straighthead scores were 5 - 6
which indicated their moderately susceptible to straighthead. The yields was
negatively related to the straighthead scores (r = -0.956, P < 0.01).
Compared to CCDR, the yield of hybrids showed their straighthead resistance at
some extent. The yields of top six entries, hybrid 33A/PB23, inbred 3053, hybrid
28s/PB22, 28s/PB24, 29s/PB24 and inbred 3222, were 10,376.4, 9991.4, 9566.7,
9334.3, 9183.9 and 9174.3 Kg/Ha, and 46.0%, 40.7%, 34.7%, 31.4%, 29.3%, and
29.5% higher than the check, respectively.